https://zr1netregistry.com RSS feeds for ZR-1 NET Registry 60 https://www.zr1netregistry.com/Information/C4ZR-1TechWrite-Ups/EngineDrivetrain/Engine/tabid/137/articleType/ArticleView/articleId/1847/Engine-Bolt-Charts.aspx#Comments 0 https://www.zr1netregistry.com/DesktopModules/DnnForge%20-%20NewsArticles/RssComments.aspx?TabID=137&ModuleID=597&ArticleID=1847 https://www.zr1netregistry.com:443/DesktopModules/DnnForge%20-%20NewsArticles/Tracking/Trackback.aspx?ArticleID=1847&PortalID=0&TabID=137 https://www.zr1netregistry.com/Information/C4ZR-1TechWrite-Ups/EngineDrivetrain/Engine/tabid/137/articleType/ArticleView/articleId/1847/Engine-Bolt-Charts.aspx LT5 Bolt Charts with suggested bolt torque, loctite and antiseize application information are included above. Based on the chart provided by Jerry's Gaskets. Click to enlarge. host1 Thu, 14 Nov 2013 20:01:00 GMT f1397696-738c-4295-afcd-943feb885714:1847 https://www.zr1netregistry.com/Information/C4ZR-1TechWrite-Ups/EngineDrivetrain/Engine/tabid/137/articleType/ArticleView/articleId/1844/Engine-Oil.aspx#Comments 0 https://www.zr1netregistry.com/DesktopModules/DnnForge%20-%20NewsArticles/RssComments.aspx?TabID=137&ModuleID=597&ArticleID=1844 https://www.zr1netregistry.com:443/DesktopModules/DnnForge%20-%20NewsArticles/Tracking/Trackback.aspx?ArticleID=1844&PortalID=0&TabID=137 https://www.zr1netregistry.com/Information/C4ZR-1TechWrite-Ups/EngineDrivetrain/Engine/tabid/137/articleType/ArticleView/articleId/1844/Engine-Oil.aspx Engine Oil 8.6 quarts (with filter change) Amsoil 10W-40 AMO Motor Oiil Bosch 3401 Filter FRAM TG 3985 Filter Mobile 1 M1-207 Filter host1 Thu, 14 Nov 2013 18:41:00 GMT f1397696-738c-4295-afcd-943feb885714:1844 https://www.zr1netregistry.com/Information/C4ZR-1TechWrite-Ups/EngineDrivetrain/Engine/tabid/137/articleType/ArticleView/articleId/216/Oil-Pressure-Sender-Reconditioning.aspx#Comments 2 https://www.zr1netregistry.com/DesktopModules/DnnForge%20-%20NewsArticles/RssComments.aspx?TabID=137&ModuleID=597&ArticleID=216 https://www.zr1netregistry.com:443/DesktopModules/DnnForge%20-%20NewsArticles/Tracking/Trackback.aspx?ArticleID=216&PortalID=0&TabID=137 https://www.zr1netregistry.com/Information/C4ZR-1TechWrite-Ups/EngineDrivetrain/Engine/tabid/137/articleType/ArticleView/articleId/216/Oil-Pressure-Sender-Reconditioning.aspx Reconditioning the oil pressure sender host1 Tue, 24 Apr 2012 02:38:00 GMT f1397696-738c-4295-afcd-943feb885714:216 https://www.zr1netregistry.com/Information/C4ZR-1TechWrite-Ups/EngineDrivetrain/Engine/tabid/137/articleType/ArticleView/articleId/214/Reinforcing-the-Air-Duct-Bellows.aspx#Comments 1 https://www.zr1netregistry.com/DesktopModules/DnnForge%20-%20NewsArticles/RssComments.aspx?TabID=137&ModuleID=597&ArticleID=214 https://www.zr1netregistry.com:443/DesktopModules/DnnForge%20-%20NewsArticles/Tracking/Trackback.aspx?ArticleID=214&PortalID=0&TabID=137 https://www.zr1netregistry.com/Information/C4ZR-1TechWrite-Ups/EngineDrivetrain/Engine/tabid/137/articleType/ArticleView/articleId/214/Reinforcing-the-Air-Duct-Bellows.aspx How to make a reinforcement for the air duct (bellows). host1 Mon, 23 Apr 2012 21:53:00 GMT f1397696-738c-4295-afcd-943feb885714:214 https://www.zr1netregistry.com/Information/C4ZR-1TechWrite-Ups/EngineDrivetrain/Engine/tabid/137/articleType/ArticleView/articleId/213/Replacing-the-Throttle-Body.aspx#Comments 1 https://www.zr1netregistry.com/DesktopModules/DnnForge%20-%20NewsArticles/RssComments.aspx?TabID=137&ModuleID=597&ArticleID=213 https://www.zr1netregistry.com:443/DesktopModules/DnnForge%20-%20NewsArticles/Tracking/Trackback.aspx?ArticleID=213&PortalID=0&TabID=137 https://www.zr1netregistry.com/Information/C4ZR-1TechWrite-Ups/EngineDrivetrain/Engine/tabid/137/articleType/ArticleView/articleId/213/Replacing-the-Throttle-Body.aspx How to remove and replace the throttle body. host1 Mon, 23 Apr 2012 19:31:00 GMT f1397696-738c-4295-afcd-943feb885714:213 https://www.zr1netregistry.com/Information/C4ZR-1TechWrite-Ups/EngineDrivetrain/Engine/tabid/137/articleType/ArticleView/articleId/212/LT5-Cam-Timing.aspx#Comments 1 https://www.zr1netregistry.com/DesktopModules/DnnForge%20-%20NewsArticles/RssComments.aspx?TabID=137&ModuleID=597&ArticleID=212 https://www.zr1netregistry.com:443/DesktopModules/DnnForge%20-%20NewsArticles/Tracking/Trackback.aspx?ArticleID=212&PortalID=0&TabID=137 https://www.zr1netregistry.com/Information/C4ZR-1TechWrite-Ups/EngineDrivetrain/Engine/tabid/137/articleType/ArticleView/articleId/212/LT5-Cam-Timing.aspx How to time the LT5 camshafts. host1 Mon, 23 Apr 2012 18:48:00 GMT f1397696-738c-4295-afcd-943feb885714:212 https://www.zr1netregistry.com/Information/C4ZR-1TechWrite-Ups/EngineDrivetrain/Engine/tabid/137/articleType/ArticleView/articleId/211/Engine-Removal.aspx#Comments 1 https://www.zr1netregistry.com/DesktopModules/DnnForge%20-%20NewsArticles/RssComments.aspx?TabID=137&ModuleID=597&ArticleID=211 https://www.zr1netregistry.com:443/DesktopModules/DnnForge%20-%20NewsArticles/Tracking/Trackback.aspx?ArticleID=211&PortalID=0&TabID=137 https://www.zr1netregistry.com/Information/C4ZR-1TechWrite-Ups/EngineDrivetrain/Engine/tabid/137/articleType/ArticleView/articleId/211/Engine-Removal.aspx How to remove the LT5 engine. host1 Mon, 23 Apr 2012 16:58:00 GMT f1397696-738c-4295-afcd-943feb885714:211 https://www.zr1netregistry.com/Information/C4ZR-1TechWrite-Ups/EngineDrivetrain/Engine/tabid/137/articleType/ArticleView/articleId/210/LT5-Cylinder-Head-Removal.aspx#Comments 8 https://www.zr1netregistry.com/DesktopModules/DnnForge%20-%20NewsArticles/RssComments.aspx?TabID=137&ModuleID=597&ArticleID=210 https://www.zr1netregistry.com:443/DesktopModules/DnnForge%20-%20NewsArticles/Tracking/Trackback.aspx?ArticleID=210&PortalID=0&TabID=137 https://www.zr1netregistry.com/Information/C4ZR-1TechWrite-Ups/EngineDrivetrain/Engine/tabid/137/articleType/ArticleView/articleId/210/LT5-Cylinder-Head-Removal.aspx How to remove the LT5 cylinder heads. host1 Mon, 23 Apr 2012 16:50:00 GMT f1397696-738c-4295-afcd-943feb885714:210 https://www.zr1netregistry.com/Information/C4ZR-1TechWrite-Ups/EngineDrivetrain/Engine/tabid/137/articleType/ArticleView/articleId/209/Oil-Cooler-Lines-Replacement.aspx#Comments 2 https://www.zr1netregistry.com/DesktopModules/DnnForge%20-%20NewsArticles/RssComments.aspx?TabID=137&ModuleID=597&ArticleID=209 https://www.zr1netregistry.com:443/DesktopModules/DnnForge%20-%20NewsArticles/Tracking/Trackback.aspx?ArticleID=209&PortalID=0&TabID=137 https://www.zr1netregistry.com/Information/C4ZR-1TechWrite-Ups/EngineDrivetrain/Engine/tabid/137/articleType/ArticleView/articleId/209/Oil-Cooler-Lines-Replacement.aspx How to remove and install replacement oil cooler lines. host1 Mon, 23 Apr 2012 16:39:00 GMT f1397696-738c-4295-afcd-943feb885714:209 https://www.zr1netregistry.com/Information/C4ZR-1TechWrite-Ups/EngineDrivetrain/Engine/tabid/137/articleType/ArticleView/articleId/208/LT5-Plenum-Removal.aspx#Comments 1 https://www.zr1netregistry.com/DesktopModules/DnnForge%20-%20NewsArticles/RssComments.aspx?TabID=137&ModuleID=597&ArticleID=208 https://www.zr1netregistry.com:443/DesktopModules/DnnForge%20-%20NewsArticles/Tracking/Trackback.aspx?ArticleID=208&PortalID=0&TabID=137 https://www.zr1netregistry.com/Information/C4ZR-1TechWrite-Ups/EngineDrivetrain/Engine/tabid/137/articleType/ArticleView/articleId/208/LT5-Plenum-Removal.aspx How to remove the LT5 plenum. host1 Mon, 23 Apr 2012 16:02:00 GMT f1397696-738c-4295-afcd-943feb885714:208 https://www.zr1netregistry.com/Information/C4ZR-1TechWrite-Ups/EngineDrivetrain/Engine/tabid/137/articleType/ArticleView/articleId/203/Fuel-Gauge-Sender-Unit-Repair.aspx#Comments 1 https://www.zr1netregistry.com/DesktopModules/DnnForge%20-%20NewsArticles/RssComments.aspx?TabID=137&ModuleID=597&ArticleID=203 https://www.zr1netregistry.com:443/DesktopModules/DnnForge%20-%20NewsArticles/Tracking/Trackback.aspx?ArticleID=203&PortalID=0&TabID=137 https://www.zr1netregistry.com/Information/C4ZR-1TechWrite-Ups/EngineDrivetrain/Engine/tabid/137/articleType/ArticleView/articleId/203/Fuel-Gauge-Sender-Unit-Repair.aspx Removing and repairing the Fuel Gauge Sender Unit host1 Sun, 22 Apr 2012 17:56:00 GMT f1397696-738c-4295-afcd-943feb885714:203 https://www.zr1netregistry.com/Information/C4ZR-1TechWrite-Ups/EngineDrivetrain/Engine/tabid/137/articleType/ArticleView/articleId/202/Fuel-Pump-Replacement.aspx#Comments 2 https://www.zr1netregistry.com/DesktopModules/DnnForge%20-%20NewsArticles/RssComments.aspx?TabID=137&ModuleID=597&ArticleID=202 https://www.zr1netregistry.com:443/DesktopModules/DnnForge%20-%20NewsArticles/Tracking/Trackback.aspx?ArticleID=202&PortalID=0&TabID=137 https://www.zr1netregistry.com/Information/C4ZR-1TechWrite-Ups/EngineDrivetrain/Engine/tabid/137/articleType/ArticleView/articleId/202/Fuel-Pump-Replacement.aspx How to remove and replace the fuel pumps. host1 Sun, 22 Apr 2012 17:28:00 GMT f1397696-738c-4295-afcd-943feb885714:202 https://www.zr1netregistry.com/Information/C4ZR-1TechWrite-Ups/EngineDrivetrain/Engine/tabid/137/articleType/ArticleView/articleId/195/Master-Cylinder-and-Actuator-Cylinder-Quality-Issue.aspx#Comments 2 https://www.zr1netregistry.com/DesktopModules/DnnForge%20-%20NewsArticles/RssComments.aspx?TabID=137&ModuleID=597&ArticleID=195 https://www.zr1netregistry.com:443/DesktopModules/DnnForge%20-%20NewsArticles/Tracking/Trackback.aspx?ArticleID=195&PortalID=0&TabID=137 https://www.zr1netregistry.com/Information/C4ZR-1TechWrite-Ups/EngineDrivetrain/Engine/tabid/137/articleType/ArticleView/articleId/195/Master-Cylinder-and-Actuator-Cylinder-Quality-Issue.aspx Symptoms: We have had a terrible time during the last few years dealing with the C4 MN6 CHS Master Cylinders (P/N 19158668) and Slave Cylinders (P/N 12509313) components in regards to meeting operational requirements of the ZF S6-40 gear shifting operation. Our livelihood at ZR51 Performance, remanufacture of the ZF S6-40 transmission, is profoundly impacted by problems incurred with C4 MN6 CHS operational problems. As a shop that mostly services C4 MN6 Corvettes, we have documented time and material loses exceeding $5,000.00 during the past two years directly caused by problems incurred when installing new GM CHS Master Cylinders (P/N 19158668) and new GM CHS Slave Cylinders (P/N 12509313) into our customer's vehicles.   Procedure: C4 Clutch Hydraulic System (CHS) component fault diagnostic and corrective action report to GM SPO Quality Group regarding latest field observations of GM Replacement CHS Master Cylinder (P/N 19158668) and Actuator Cylinder (P/N 12509313) Quality Assurance. We have noticed during the last 45 days only the first two (2) out of the last twelve (12) CHS Actuator Cylinders (P/N 12509313) had their seals installed backwards. Unfortunately with this (seal direction) quality assurance correction we have noticed another quality assurance issue has developed. Failure Analysis (P/N 12509313): Out of the last ten CHS Actuator Cylinders (P/N 12509313) disassembled for QA inspection, eight (8) out of ten (10) of these units were found to have the seal compromised. Upon further inspection of these failed units, it was determined that the damage to the seals had occurred during manufacturing when the piston assemblies were installed into the cylinder assemblies. Trace evidence indicates that Assembly personnel were/are not using a mandrel device to ease-load the piston assemblies into the Actuator Cylinder assemblies causing the seal to in some cases fold over backwards and tear or sheer off large portions of the seal lip while being inserted into the bore. We observed that on all units (P/N 12509313) there is a sharp burr edge present at the bore opening where a 45 degree chamfer relief is machined into the leading edge of the bore. This sharp edge happens to be at the major diameter edge of the 45 degree chamfer relief which only poses a threat to the seal integrity during insertion when a mandrel device is not utilized. Operation of the MN6 CHS while having a compromised Actuator Cylinder seal will cause wide range of problems ranging from reduced longevity and notchy shifting to a state where operation of the CHS is not even possible. Corrective Action (P/N 12509313): It is an industry standard practice to employ the use of a mandrel device whenever inserting a piston/seal assembly into a cylinder bore assembly especially when the bore entry has sharp edges present which pose a hazard to the integrity of the piston seal(s) during the insertion process. To fabricate a mandrel device for this particular assembly process cut a section of tubing from an existing Actuator Cylinder, machine the end faces flat and break (remove) all sharp edges. With ample lubricant, load piston/seal assembly into mandrel feeding in direction where seal is gathered in gently by ramping smallest to largest diameter of seal. Place the mandrel with piston protruding slightly for ease of alignment up to the cylinder bore opening and load into the bore by pushing with finger. Failure Analysis (P/N 19158668): The C4 MN6 CHS Master Cylinder (P/N 19158668) Hydraulic Fluid Reservoir (last 15 out of 20 samples) have been found to have defects in the bulkhead (seal) fitting portion of the plastic molded component. From an operational standpoint, this defect reduces the CHS operational level of effectiveness by allowing air to be drawn into the system during each actuation stroke at the bulkhead seal but does not allow hydraulic fluid to leak out. With the reservoir lid and moisture barrier removed, bubbles can be seen rising from the Master cylinder chamber just about every clutch pedal stroke even after the CHS has been reverse bled with all air removed from CHS. This causes stiff or notchy shifting during operation of ZF S6-40 manual transmission. Corrective Action (P/N 19158668): Check the Extrusion Mold surfaces for imperfections at the barb portion bulkhead fitting, reworking if necessary. Review the production process requirements regarding necessary component cooling before removing component from the molding fixture. add photos here...  Author Bill Boudreau (ZFDoc)   host1 Thu, 19 Apr 2012 22:08:00 GMT f1397696-738c-4295-afcd-943feb885714:195 https://www.zr1netregistry.com/Information/C4ZR-1TechWrite-Ups/EngineDrivetrain/Engine/tabid/137/articleType/ArticleView/articleId/194/Clutch-Master-And-Slave-Hydraulic-Cylinders-Leakdown-test.aspx#Comments 3 https://www.zr1netregistry.com/DesktopModules/DnnForge%20-%20NewsArticles/RssComments.aspx?TabID=137&ModuleID=597&ArticleID=194 https://www.zr1netregistry.com:443/DesktopModules/DnnForge%20-%20NewsArticles/Tracking/Trackback.aspx?ArticleID=194&PortalID=0&TabID=137 https://www.zr1netregistry.com/Information/C4ZR-1TechWrite-Ups/EngineDrivetrain/Engine/tabid/137/articleType/ArticleView/articleId/194/Clutch-Master-And-Slave-Hydraulic-Cylinders-Leakdown-test.aspx Procedure: The following procedure may help to solve a "notchie" gear issue. As long as you haven't heard any gear clash (grinding) when shifting to the problematic gear. If you have already experienced gear clash when shifting into the affected gear then it is unlikely that any oil brand will remedy the problem of notchiness even after correcting a faulty clutch hydraulic system. Once the dogteeth start developing clash related burrs on them, replacement of the gear and ring usually is required along with replacement of the synchronizer. Leak Down Test Of The Clutch Master And Slave Hydraulic Cylinders How to check out the operational condition of the hydraulic clutch system: Thoroughly bleed the system with GM P/M 12345347 hydraulic clutch fluid. Simulate the vehicle being parked on an incline for 12-24 hours with the front end at least 1 foot higher than the rear. Lower the vehicle and start the engine. Do not cycle (pump) the clutch several times before the next step. Try to put it into reverse when it first gets started (cold). Note: Difficulty getting into reverse when in this condition indicates that the clutch master cylinder is not at 100%. Repeat steps 1-5 of this procedure except with rear end raised. Note: This will be the leak down test for the slave cylinder. It is possible that the slave cylinder can developed a build up of deposits in the barrel at the fully depressed piston seal position causing a hang up of the actuation seal under mild depression rate cycling of the cylinder. Rapid and complete depression of the clutch will cause the seal to stretch momentarily at the fully depressed end of the cycle causing the actuation stroke to cycle slightly deeper than when cycling the clutch at a slower rate. This condition may be corrected with a good bleeding of the system. I have rebuilt many ZF S6-40s which had badly burred and worn reverse gear synchronizer dog teeth. Reverse is usually the first gear to be used after cold startup and tells the most accurate story of the clutch hydraulic system's condition. If either cylinder is below standard, I highly recommend that the master and slave cylinder are replaced as a set. The key to optimal shifting performance for your ZF: When servicing the clutch master cylinder, be sure to flush clean the reservoir with clean new fluid. Pay EXTREME ATTENTION to getting the reservoir LEVEL BETWEEN the HIGH-LOW marks (ABSOLUTELY NO LOWER OR NO HIGHER) WHEN the weather barrier BLADDER-SEAL is SEATED and the reservoir screw-on cap is in place. Author: Bill Boudreau (ZFDoc)   host1 Thu, 19 Apr 2012 21:24:00 GMT f1397696-738c-4295-afcd-943feb885714:194 https://www.zr1netregistry.com/Information/C4ZR-1TechWrite-Ups/EngineDrivetrain/Engine/tabid/137/articleType/ArticleView/articleId/192/Clutch-Master-Cylinder-Installation.aspx#Comments 1 https://www.zr1netregistry.com/DesktopModules/DnnForge%20-%20NewsArticles/RssComments.aspx?TabID=137&ModuleID=597&ArticleID=192 https://www.zr1netregistry.com:443/DesktopModules/DnnForge%20-%20NewsArticles/Tracking/Trackback.aspx?ArticleID=192&PortalID=0&TabID=137 https://www.zr1netregistry.com/Information/C4ZR-1TechWrite-Ups/EngineDrivetrain/Engine/tabid/137/articleType/ArticleView/articleId/192/Clutch-Master-Cylinder-Installation.aspx How to install a new clutch master cylinder. host1 Wed, 18 Apr 2012 22:01:00 GMT f1397696-738c-4295-afcd-943feb885714:192 https://www.zr1netregistry.com/Information/C4ZR-1TechWrite-Ups/EngineDrivetrain/Engine/tabid/137/articleType/ArticleView/articleId/112/ZR-1-No-Start-issue.aspx#Comments 1 https://www.zr1netregistry.com/DesktopModules/DnnForge%20-%20NewsArticles/RssComments.aspx?TabID=137&ModuleID=597&ArticleID=112 https://www.zr1netregistry.com:443/DesktopModules/DnnForge%20-%20NewsArticles/Tracking/Trackback.aspx?ArticleID=112&PortalID=0&TabID=137 https://www.zr1netregistry.com/Information/C4ZR-1TechWrite-Ups/EngineDrivetrain/Engine/tabid/137/articleType/ArticleView/articleId/112/ZR-1-No-Start-issue.aspx Causes and possible cures for the "No Start" issue. host1 Wed, 04 Apr 2012 22:36:00 GMT f1397696-738c-4295-afcd-943feb885714:112 https://www.zr1netregistry.com/Information/C4ZR-1TechWrite-Ups/EngineDrivetrain/Engine/tabid/137/articleType/ArticleView/articleId/101/Secondary-Port-Vacuum-Diagnosis.aspx#Comments 1 https://www.zr1netregistry.com/DesktopModules/DnnForge%20-%20NewsArticles/RssComments.aspx?TabID=137&ModuleID=597&ArticleID=101 https://www.zr1netregistry.com:443/DesktopModules/DnnForge%20-%20NewsArticles/Tracking/Trackback.aspx?ArticleID=101&PortalID=0&TabID=137 https://www.zr1netregistry.com/Information/C4ZR-1TechWrite-Ups/EngineDrivetrain/Engine/tabid/137/articleType/ArticleView/articleId/101/Secondary-Port-Vacuum-Diagnosis.aspx LT5 Secondary Port Operation & Vacuum Diagnosis Before getting into diagnosing the LT5 engine's secondary port vacuum system, I thought it would be a good idea to take this opportunity to clear up a few popular misconceptions about the LT5 engine and establish a basis for understanding what the engine is and how it operates. The heart of the 1990-1995 ZR-1 Corvette is the LT5 engine; one of the most technologically advanced engines of its time. A lot of misconception seems to exist about the history and operation of the LT5 engine. Rather than go into great detail here about the engine, a few facts should be addressed up front: The LT5 engine is an all aluminum, double overhead cam design with 32 valves, and 16 fuel injectors (8 primary, 8 secondary). Power output was as follows:         1990 - 1992: HP: 375 hp @ 6,000 rpm, Torque: 370 ft-lbs @ 4,800 rpm         1993 - 1995: HP: 405 hp @ 5,800 rpm, Torque: 385 ft lbs @ 4,800 rpm The LT5 motor was designed and engineered by both GM Powertrain in Detroit, MI *and* Lotus Engineering in Hethel, England. It was not solely designed by Lotus Engineering. It should be noted that at the time, Lotus was owned by General Motors. The motor was built by Mercury Marine in Stillwater, Oklahoma. Mercury Marine was chosen by GM to build the LT5 due to their expertise in building aluminum outboard motors and their ability to manufacture engines on a small scale. Valet Key ("Power Key") Since there is a lot of misunderstanding about what the purpose of the Valet Key is and how it works, I thought I would include the following from page 6E3-C2-2 of the 1990 Corvette Service Manual: "The driver can select two engine power modes, "FULL" or "NORMAL" power, with a a console mounted key switch. This switch is wired into the ECM, and allows the driver to determine the engine output by controlling secondary port throttle valves, secondary injectors and secondary fuel pump operation. When the key switch is in the "FULL" power position, the "Full Engine Power" light, located in the driver information center, is illuminated. In the "NORMAL" power position, the ECM does not allow the secondary port throttle valves to be opened, or allow the secondary injectors to be turned "ON." In the "FULL" power position, the ECM enables secondary operation only if no trouble codes are stored and other criteria are met..." It should be noted that with the key in the "NORMAL" power position, the engine is limited to approximately 210 horsepower. The following information below comes from Tim Holland, a Lotus Engineer who started at Lotus in March of 1985 and began work on the LT5 project in July of 1985. Among his other responsibilities for the project, he served as the mechanical/calibration engineer as well as the emissions engineer responsible for meeting EPA requirements. Secondary Port Throttle Operation In order for the secondary port throttle valves to open, the following parameters must be met:    Coolant Temperature  20 Deg C (68 Deg F) or above  Oil Temperature  20 Deg C (68 Deg F) or above  System Voltage  10 V. or above  Trouble Codes (SES Light)  None  Power Key  On  Throttle versus RPM  See diagrams below   When these parameters are met, the ECM will signal the ports to open and wait for .5 seconds before turning on the secondary injectors. As the secondary injectors share the same drivers as that of the primaries, the pulse width signals are halved when the secondaries operate. As shown in the diagrams (below), there are three different styles of driving which will operate the port throttles: Ref. line A-B. Constant throttle position with a rising rpm. At the point the arrow crosses into the 'Port Throttle Opening Region' (top left shaded area) the port throttles open and the secondary injectors start firing. Ref. line C-D. Constant rpm with increasing throttle position - logic as above. Combination of the above: i.e. increasing throttle and rpm - logic as above. Secondary Port Throttle   Vacuum Leak Diagnosis One of the easiest ways to determine if you have a secondary port vacuum leak is to simply turn the ignition key to the on position but do not start the car. You should hear the Secondary Port Throttle Vacuum Pump turn on. If you don't hear the pump turn on, it's possible that it could be burned out. The pump is located in front of the coolant reserve tank right underneath the headlight bucket on the passenger side of the engine compartment (see Figure 1 below). The pump should run for 5-10 seconds to prime the system and then turn off.     Figure 1 - Secondary Port Vacuum Pump - Part #10098474 (Also check Part #10098493) Unfortunately the quality of this photo is not as good as I'd like but good enough for this example. This is the secondary port vacuum pump located under the passenger side headlight bucket So what does this pump do? There is a vacuum reservoir located under the plenum. If the vacuum level in the reservoir drops below 41 kPa (12" Hg) while the secondary port throttle valves are open, the pump is turned "on" by a vacuum switch to supplement engine vacuum. If the pump cycles on and off every few seconds or it runs continuously, chances are, you have a vacuum leak somewhere in the system. To begin, take a ride to your local Sears Automotive Center and purchase a hand held vacuum pump as shown below in Figure 2. This pump is extremely invaluable and will help you to locate the source of the vacuum leak. The pump comes with all necessary hose adapters.   Figure 2 - Handheld Vacuum Pump Figure 3 below shows the vacuum connection between the line going to the pump (right - see pump below) and the left hand vacuum system going underneath the plenum (left).     Figure 3 - Vacuum Connection Disconnect the hose at this connection. At this point, with the engine key in the "On" position, the pump should turn on and run constantly. (Another way of verifying that the pump is operating correctly) Connect your hand held vacuum pump to the line going under the plenum and bring the system up to 10-12 Hg. If the system does not have a leak, the gauge needle will stay at that level. If there is a leak, it will slowly move back to zero. If there is no leak under the plenum, repeat the procedure at the other end of the hose going to the pump to determine if there is a leak on that side of the system. If you have a leak under the plenum, it's time to remove the plenum from the top of the engine. To do this, follow the procedure outlined in your service manual for plenum removal. You should always have a service manual for your model year prior to conducting any diagnostic tests or repairs. If you don't have a service manual for your car, you can purchase one from companies such as MidAmerica, Ecklers or Helm. To put everything in perspective, below is an LT5 engine with the plenum on (Figure 4 below). With the plenum off, it's a much different picture than what you see here!   Figure 4 - LT5 Engine Prior to Plenum Removal Figure 5 - Secondary Port Vacuum Hose Assembly In this photo, you can see the entire secondary port vacuum hose assembly (Part #10146221). At the lower right you can see the connector that is pointed to in the picture above. The upper left hand corner connects to another connector under the ECM.     Figure 6A - Plenum Removed Key: Primary Port Secondary Port Secondary Port Control Solenoid Secondary Port Vacuum Actuator (Part #1996743) (just to the right, you can see the metal arm and attachment going to the injector housing Fuel Rail Assembly with injectors inserted into the Injector Housing     Figure 6B - Close-up of Primary and Secondary Ports Figure 6B is a closeup view of a primary and secondary port. The primary port is on the right and the secondary port is on the left. You can see the butterfly valve inside the secondary port. Below is a picture of the LT5 engine throttle body. Figure 7- LT5 Throttle Body In the center of the throttle body, at the bottom, you see the primary throttle valve which is 22 mm (0.87 in.) in diameter. Above are the two larger secondary valves which are 59 mm (2.32 in.). The secondary throttle valves begin opening when the primary valve is 80% open and are completely open at full throttle. From page 2-9, Corvette LT5 Fuel and Emissions, Course No. 16009.14-1: "The primary throttle valve is operational when the vehicle speeds are less than approximately 113 km/h (70 mph) (level terrain cruise). The secondary throttle valves are opened at approximately 80 degrees of primary throttle opening."     Figure 8 - Top View, Plenum Removed Key: Secondary Port Vacuum Reservoir (Part #10067563) Crankcase Ventilation Cover Secondary Port Vacuum Actuators (Part #1996743) Ignition Coil Packs (starter is underneath them) Vacuum connector which plugs into the Secondary Port Vacuum Solenoid Crankcase Breather Hoses (Part #s 10110908, 10110907) In this picture you can see the top of the Crankcase Ventilation Cover. For those of you with 1990 ZR-1s, this is a common area of oil seepage. The cover bolts were not torqued properly from the factory and can loosen up over time. If you notice the top of your engine V is damp with oil, chances are, this is the source. It's a good idea to replace the Crankcase Breather Gasket underneath (Part #10168682) and retorque the bolts.   Figure 9 - Top view, from driver's side   Key: Vacuum Solenoid with conical air filter (Part #1997222), Conical Air Filter Part #: 10159525 Injector Housing Fuel Rail Figure 9 is a different angle taken from the driver's side of the engine looking down at the vacuum solenoid.   Figure 10 - Secondary Port Solonoid From LT5 Fuel and Emissions, a GM STG Training Course Book, pages 2-12 and 2-13: Secondary Port Control Solenoid This solenoid is used by the ECM to control the application of vacuum to the secondary port throttle valve actuators. The solenoid is normally closed and is opened ("ON") when the ECM provides the ground path. The solenoid is located under the intake plenum at the front of the cylinder block valley, near the left hand side of the vacuum reservoir. The sensor is connected to the engine wiring harness by a two terminal blue connector. (Refer to Figure 2-15)." Figure 11 - Secondary Port Throttle Valves, Actuator and Linkage Secondary Port Throttle Valves, Actuator and Linkage "The secondary port throttle valves are used to provide additional control of airflow to the cylinders. The valves are vacuum operated, and controlled by an ECM actuated solenoid, based on input signals from the Throttle Position Sensor (TPS), engine RPM, engine oil temperature sensor and Manifold Absolute Pressure (MAP) sensor. Vacuum is supplied through the vacuum reservoir and vacuum pump. (Refer to Figure 2-14). In operation, the secondary port throttle valves are closed during low engine speeds and loads, allowing no air path to each cylinder. Additional air is allowed to enter the cylinders at higher RPM when the following criteria are met: When the TPS indicates to the ECM that the driver has pushed down on the accelerator pedal far enough, and the oil temperature sensor indicates engine oil temperature is within an acceptable range, the ECM will turn "ON" the secondary port throttle actuators through the secondary port throttle control solenoid allowing engine vacuum to be applied to the actuators to open the valves. At the same time, the secondary injectors are turned "ON" to provide additional fuel flow to maintain the correct air/fuel ratio for maximum power (12:1). The secondary port throttle valves are located in the right and left hand cylinder head (four plates per head). The actuators are mounted to brackets attached near the center of each cylinder head. A common linkage incorporates each set of four throttle valves together to the actuators which will open all throttle valves in unison (Refer to Figure 2-14)." At this point, if you trace the various connections of the vacuum lines, you'll see that they go to the secondary port throttle valve actuators, vacuum solenoid and vacuum reservoir. These are the three main areas for vacuum leaks to occur due to mechanical failure of these parts. Test the Secondary Port Throttle Vacuum actuators by disconnecting the vacuum line, connecting your vacuum pump and applying enough vacuum until you see the secondary port throttle valve plates open. Once open, they should stay open until you release the vacuum from the pump. If they slowly start to close, chances are the secondary port throttle valve actuator needs to be replaced. Conduct this procedure for both actuators. Test the Vacuum Reservoir by connecting your vacuum pump to one inlet and blocking the other. Apply 10-12 Hg of vacuum. If the gauge starts to decrease, replace the vacuum reservoir. Test the vacuum solenoid which is in front of the left hand side of the vacuum reservoir. Make sure all connections but one to the solenoid are blocked and connect your vacuum pump to the free connection. Apply a vacuum as described in step two. If the gauge decreases and vacuum is lost, the solenoid needs to be replaced. Case in Point Recently, I noticed that my secondary port vacuum pump was cycling on and off when the ignition key was turned on. I started off by confirming that a vacuum leak existed under the plenum. After removing the plenum I checked the vacuum at many of the connections and found that the vacuum solenoid was not holding a vacuum. Upon replacement, the vacuum pump primed the system, turned off and did not continue cycling on and off as before. Tips Keep in mind that if you run vacuum checks on the three main areas I outlined above and they all pass the vacuum check, it is possible that you have a leak somewhere else in the vacuum lines. The vacuum line system consists of several hoses and check valves that are routed throughout the "V" under the plenum. Make sure that before you put the plenum back on the engine, all vacuum lines and electrical connectors are reconnected! This is very important because all it takes is one failed connection and you will be pulling the plenum back off to determine why the secondaries don't work at all. As you can see, the most difficult part of diagnosing and repairing most secondary port vacuum leaks is the removal of the plenum. Once you get the plenum off, you have easy access to most of the key components that control secondary port vacuum operation. Good luck!     Author: Rob Loszewski - Corvette Action Center host1 Sun, 01 Apr 2012 22:39:00 GMT f1397696-738c-4295-afcd-943feb885714:101 https://www.zr1netregistry.com/Information/C4ZR-1TechWrite-Ups/EngineDrivetrain/Engine/tabid/137/articleType/ArticleView/articleId/80/GM-Clutch-Hydraulic-System-Actuator.aspx#Comments 2 https://www.zr1netregistry.com/DesktopModules/DnnForge%20-%20NewsArticles/RssComments.aspx?TabID=137&ModuleID=597&ArticleID=80 https://www.zr1netregistry.com:443/DesktopModules/DnnForge%20-%20NewsArticles/Tracking/Trackback.aspx?ArticleID=80&PortalID=0&TabID=137 https://www.zr1netregistry.com/Information/C4ZR-1TechWrite-Ups/EngineDrivetrain/Engine/tabid/137/articleType/ArticleView/articleId/80/GM-Clutch-Hydraulic-System-Actuator.aspx Information on issues with the GM Clutch Hydraulic System Actuator. host1 Fri, 23 Mar 2012 22:36:00 GMT f1397696-738c-4295-afcd-943feb885714:80 https://www.zr1netregistry.com/Information/C4ZR-1TechWrite-Ups/EngineDrivetrain/Engine/tabid/137/articleType/ArticleView/articleId/79/Reading-DTCs-1994-1995.aspx#Comments 2 https://www.zr1netregistry.com/DesktopModules/DnnForge%20-%20NewsArticles/RssComments.aspx?TabID=137&ModuleID=597&ArticleID=79 https://www.zr1netregistry.com:443/DesktopModules/DnnForge%20-%20NewsArticles/Tracking/Trackback.aspx?ArticleID=79&PortalID=0&TabID=137 https://www.zr1netregistry.com/Information/C4ZR-1TechWrite-Ups/EngineDrivetrain/Engine/tabid/137/articleType/ArticleView/articleId/79/Reading-DTCs-1994-1995.aspx Thanks to Erle, Hib, Ed, James, and even Bruce, I've figured out how to read Diagnostic Trouble Codes on the 1994-95 MY ZR-1.   The 1994 service manual is confusing on this issue. It says you cannot read the codes on cars with the 16 pin connector under the dashboard right above the pedals. The reason for this is because the 94-95 LT1 cars were wired up for OBD II, which was required in 1996. Since the LT5 was going to be discontinued after MY1995, there was no OBD II implemented on the LT5, but it got the 16 pin connector anyway.   I was able to read the codes on my 94 ZR-1 by grounding the #6 pin by connecting it to the #5 pin. If you look at the connector, it is trapezoidal in shape. The wide part is the top, the narrow part the bottom. The pin on the top left is #1, the top right is #8.     It's simple enough to use an unfolded paper clip to make the connection. Having done the above, turn the ignition key to the "on" position, but do not start the engine. Every relay on the car comes on (except the fuel pumps), so don't be alarmed if you've never done this. The "Service Engine Soon" light will flash a code 12 three times. It will flash once, then pause, then flash twice, then a long pause, then repeats two more times. Code 12 indicates everything is working. After the code 12 flashes three times, the SES light will flash out any DTCs that have been set three times each, starting with the highest numerically. If the SES flashes four times, then pauses, then flashes five times, then it's DTC 45. Follow the service manual for diagnosis and corrective action. Disclaimer: I provide the above information to save any 94-95 owners some time figuring out how to read DTCs on their ZR-1s. Use the information at your own risk. If you're not comfortable with that, please take your car to a qualified technician. host1 Fri, 23 Mar 2012 22:29:00 GMT f1397696-738c-4295-afcd-943feb885714:79 https://www.zr1netregistry.com/Information/C4ZR-1TechWrite-Ups/EngineDrivetrain/Engine/tabid/137/articleType/ArticleView/articleId/78/Engine-StumblesDies.aspx#Comments 4 https://www.zr1netregistry.com/DesktopModules/DnnForge%20-%20NewsArticles/RssComments.aspx?TabID=137&ModuleID=597&ArticleID=78 https://www.zr1netregistry.com:443/DesktopModules/DnnForge%20-%20NewsArticles/Tracking/Trackback.aspx?ArticleID=78&PortalID=0&TabID=137 https://www.zr1netregistry.com/Information/C4ZR-1TechWrite-Ups/EngineDrivetrain/Engine/tabid/137/articleType/ArticleView/articleId/78/Engine-StumblesDies.aspx Information on the cause of Engine stumbles. host1 Fri, 23 Mar 2012 22:27:00 GMT f1397696-738c-4295-afcd-943feb885714:78 https://www.zr1netregistry.com/Information/C4ZR-1TechWrite-Ups/EngineDrivetrain/Engine/tabid/137/articleType/ArticleView/articleId/77/Upgrades.aspx#Comments 1 https://www.zr1netregistry.com/DesktopModules/DnnForge%20-%20NewsArticles/RssComments.aspx?TabID=137&ModuleID=597&ArticleID=77 https://www.zr1netregistry.com:443/DesktopModules/DnnForge%20-%20NewsArticles/Tracking/Trackback.aspx?ArticleID=77&PortalID=0&TabID=137 https://www.zr1netregistry.com/Information/C4ZR-1TechWrite-Ups/EngineDrivetrain/Engine/tabid/137/articleType/ArticleView/articleId/77/Upgrades.aspx Information on engine upgrades made between different years. host1 Fri, 23 Mar 2012 22:25:00 GMT f1397696-738c-4295-afcd-943feb885714:77 https://www.zr1netregistry.com/Information/C4ZR-1TechWrite-Ups/EngineDrivetrain/Engine/tabid/137/articleType/ArticleView/articleId/76/Chain-Tensioner-Rattles.aspx#Comments 1 https://www.zr1netregistry.com/DesktopModules/DnnForge%20-%20NewsArticles/RssComments.aspx?TabID=137&ModuleID=597&ArticleID=76 https://www.zr1netregistry.com:443/DesktopModules/DnnForge%20-%20NewsArticles/Tracking/Trackback.aspx?ArticleID=76&PortalID=0&TabID=137 https://www.zr1netregistry.com/Information/C4ZR-1TechWrite-Ups/EngineDrivetrain/Engine/tabid/137/articleType/ArticleView/articleId/76/Chain-Tensioner-Rattles.aspx Information on the chain tensioner rattles heard with the LT5. host1 Fri, 23 Mar 2012 22:22:00 GMT f1397696-738c-4295-afcd-943feb885714:76 https://www.zr1netregistry.com/Information/C4ZR-1TechWrite-Ups/EngineDrivetrain/Engine/tabid/137/articleType/ArticleView/articleId/75/Plenum-Removal.aspx#Comments 1 https://www.zr1netregistry.com/DesktopModules/DnnForge%20-%20NewsArticles/RssComments.aspx?TabID=137&ModuleID=597&ArticleID=75 https://www.zr1netregistry.com:443/DesktopModules/DnnForge%20-%20NewsArticles/Tracking/Trackback.aspx?ArticleID=75&PortalID=0&TabID=137 https://www.zr1netregistry.com/Information/C4ZR-1TechWrite-Ups/EngineDrivetrain/Engine/tabid/137/articleType/ArticleView/articleId/75/Plenum-Removal.aspx How to remove the LT5 Plenum. host1 Fri, 23 Mar 2012 22:18:00 GMT f1397696-738c-4295-afcd-943feb885714:75 https://www.zr1netregistry.com/Information/C4ZR-1TechWrite-Ups/EngineDrivetrain/Engine/tabid/137/articleType/ArticleView/articleId/74/Flywheel-Concerns.aspx#Comments 1 https://www.zr1netregistry.com/DesktopModules/DnnForge%20-%20NewsArticles/RssComments.aspx?TabID=137&ModuleID=597&ArticleID=74 https://www.zr1netregistry.com:443/DesktopModules/DnnForge%20-%20NewsArticles/Tracking/Trackback.aspx?ArticleID=74&PortalID=0&TabID=137 https://www.zr1netregistry.com/Information/C4ZR-1TechWrite-Ups/EngineDrivetrain/Engine/tabid/137/articleType/ArticleView/articleId/74/Flywheel-Concerns.aspx Information regarding concerns with the stock flywheel. host1 Fri, 23 Mar 2012 22:13:00 GMT f1397696-738c-4295-afcd-943feb885714:74 https://www.zr1netregistry.com/Information/C4ZR-1TechWrite-Ups/EngineDrivetrain/Engine/tabid/137/articleType/ArticleView/articleId/73/ClutchFlywheel-Replacement.aspx#Comments 1 https://www.zr1netregistry.com/DesktopModules/DnnForge%20-%20NewsArticles/RssComments.aspx?TabID=137&ModuleID=597&ArticleID=73 https://www.zr1netregistry.com:443/DesktopModules/DnnForge%20-%20NewsArticles/Tracking/Trackback.aspx?ArticleID=73&PortalID=0&TabID=137 https://www.zr1netregistry.com/Information/C4ZR-1TechWrite-Ups/EngineDrivetrain/Engine/tabid/137/articleType/ArticleView/articleId/73/ClutchFlywheel-Replacement.aspx Information on replacing the clutch/flywheel. host1 Fri, 23 Mar 2012 22:10:00 GMT f1397696-738c-4295-afcd-943feb885714:73