Finally resolved.

It was the IAC valve. I had check its resistance and made sure it wasn't clogged, but I did the electrical tests when it was just sitting. I took it to some mechanics that attached a diagnostic machine and got readings upon start up. Turns out that when my car was having trouble the IAC was putting out 10,000 ohms. Replaced it and all is well.

 

Good job!

Thanks for posting back with the final fix. These issues can be difficult and time consuming to resolve at times.

 

4cylinder - CA emissions - I have changed my EGR and IAC and throttle body gasket along with a host of other things like timing belt, water pump, coolant temp sensor, fuel filter, O2 sensor (top one) air filter, tune up, motor mounts, exhaust system from engine back, if there are vacuum leaks cannot find them - engine still idles/vibrates rough - at idle it is at the line below 1000 RPMs....it sometimes ranges at between that line and 1000, but it eventually settles at that line (I think it is 800) and when it is at 800 RPMs the engine idles rough - other than that the car runs great, but it has been incredibly frustrating to find out what is causing the problem.


Any suggestions?


Car does not leak or burn oil and it does not overheat.