ZR-1 Maintenance Tips

General Maintenance

by Jim VanDorn


The most common call we receive by far is from a confused ZR1 owner. After years of reading everything from which thermostat to use, to what type of spark plug is best, the average owner is totally and completely confused...and for good reason. There are many varied opinions of what is best for our cars but that may depend greatly on how you use your ZR1.


After seven years plus, many ZR1's are finally accruing some mileage. We have had the opportunity to closely inspect many engines with a variety of types of use from normal street driving to severe "weekend" use (track time). Compiling this information we can now offer the ZR1 owner some observations. One rule we've adopted after hearing so many owners say the same thing is the "DIMWIT" or "Darn, if I didn't Mess With IT" rule. In other words, if you didn't have a problem, then what are your intentions in the first place? To date, the only company known to have a fleet of engineering ZR1's to test with was GM and it's affiliates.


Therefore, we must ask ourselves if their suggested procedures and parts recommendations should have a considerable amount of merit. Obviously they do, but on the other hand, there are no doubt areas for improvement. Although we will begin our segment discussing the routine and normal maintenance of the ZR1, there are many areas where an upgrade will be suggested.


Please understand that these are personal opinions and experiences and are not intended to conflict with service procedures outlined in the appropriate service manual.

Many systems aboard the ZR1 are monitored by the Electronic Control Module (ECM). Theoretically, when a monitored system moves out of a predetermined range, the SES light will come on. The SES light will also appear if an electrical short or open in a monitored circuit occurs. There are also several common reasons for this warning to appear.

On all year models, if the SES comes on during hard acceleration, then most probably a code 61, Secondary Throttle system error has occurred. Test you vacuum pump (located in the right front headlight cavity) by turning on both ignition and power keys (do not start the engine) and disconnecting the secondary vacuum connection coming from the pump. The pump should turn on immediately and run continuously. Place a finger over the open line and the pump should suck down and quit running. Check all other vacuum connections. Particular to the '93 model year, we have seen a tremendous amount of problems with the Exhaust Gas Recirculation (EGR) systems. This may also be compounded by a faulty PROM (Programmed Read Only Memory) calibration. There is an updated replacement PROM available from your dealer.

Note: When the SES is illuminated, both the cruise control and secondary throttle systems will become inoperative.

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