I did search. Promise. But nothing jumped out at me that said start here. 89 350 tpi. New distributor, plugs, injectors, tps, cts, iac. Fans come on when the key clicks over (I know shouldnt bone stock). Engine idles high over 1500 for quite a while when started. Put in drive it dies. Let it warm, fan speed slows, idle drops and wobbles between 900 and 700. Will drive but not well. When fan is off...purrs so beautiful. I did try a reset of the iac. Maybe it didn't take? But from looking it seems only the ecm can control fans. No codes either. When its warm it can run great, until that fan kicks on and I get erratic driveablity due to the fluctuating rpms. Appreciate any insight one might have. Thanks

 

High idle sounds like vacuum leaks. Issues with fans on could be excessive current draw from bad motor(s). Sounds like your wiring has been hacked, so could also be bad wiring / incorrect stuff going on there. I'd be comparing what you've got going on at the relays near the battery with the electrical diagrams in the factory service manual. If you take some pictures of what's going on at the fan wiring we might be able to diagnose more.

 

Thanks. I did a smoke test for vacuum and nothing. It didn't do this before I pulled the top of the motor off and replaced those sensors so I can't say it was something someone else did. All of which has me quite perplexed. Never thought fan speed could affect idle speed. Its not visa versa. Plus kicking on at ACC isn't right and didn't happen previous.

 

I've had that happen in other kinds of cars.

It's a grounding issue. Usually the engine is not electrically bonded to the chassis well enough. Voltage drop in the connection. (or lack of it) The high current from the fans causes the voltage on the engine and the voltage on the chassis to be different. The O2 sensor in particular gets affected because the voltages it works with are so low to begin with, that even a small error caused this way, totally distorts its signal.

Try adding a short battery cable type of connection between the engine block and some convenient place on the "frame" or radiator core support. You can get things like a #4 18" long cable with eye terminals at both ends hanging on cards in the battery dept at the parts stores, that work perfect for this.

 

Thank you! That is something I wouldnt have considered.