I have a 1985 IROC-Z 305 TPI 215 HP. This car is all stock only with the cat removed. This car will over heat and cook over one time and then the next the fan comes on and no problem. also when the problem is there the idle runs up around 1500 but when the problem disappears the idle is about 700.
The check engine light code is 53 egr valve for carb, an over voltage for fuel injected as per my Haynes manual. The temp gauge works, the fans good and the relay is working fine. I have been looking for a vacume leak but have not found one. Should I just start replacing sensors till I find the bad one? Or does anybody have any suggestions? I have read about the switch on the dash for the fan That would help with the over heating problem but not the high idle. Also I am trying to keep this car as original as possible. I am looking for any ideas or suggestions

 

Never mind. I found the problem. With all the reading I did seems like everybody keeps saying a sensor or fan switch pulls in the relay. Well I guess I have a rare iroc because the ecm controls the fan relay. I ended up replacing the ecm an the code 53 is no longer, an the fan comes on an off automatically and the motor runs alot smoother an better.

 

Almost all TPI cars used the ECM to power the primary fan and fan switch to control the secondary fan. That said, I'm glad you got it fixed!

 

Reasonably sure 85-86 tpi only had a single fan Ozz though, ecm controlled still, as you said. 87 had tacked on harness. 88+ the second an was integrated to production wiring.

 

Thank you guys my 86 iroc got totaled because someone did not feel like stopping at a stop sign. Found this 85 iroc in storage for more than 10 years. Even though been pulling out my hair at times been able to fix everything myself. Taking it to my first show today.