Idle Air Control, Air Vacume or ECM

Hi Jacobandnickolas

When I bought this car every thing OK but I noticed on thing strange that is when I switch A/C on idle speed the engine slow down up to 500 to 600 rpm I thought that IAC valve is not working of faulty, I removed and found that the lower hole (shutter) was closed by some hard glue then I bought a new IAC with gasket and fit it. I started the car the engine run very high speed up to 2000 rpm or more, so to use the car I removed the new IAC valve and put back the old one. I checked all pipes for leak of air every thing is OK. But the A/C problem is still, any suggestion.

Thank you. Sayed Ali

NO it is fix type but I noticed when I connect the three wires plug to the new IAC without fitting it to engine it is always opened more than half way at normal engine speed with the old one fitted to engine.

See attached immage

Hi Jacobandnickolas
Yes you are right because the PCM ECM is sending interrupted negative pulses on wire no. 3 ( checked by test lamp ) which make the IAC open and close rapidly. What do you suggest is there a way to rest the PCM to original condition or shall I take it to a specialist. And if the problem in the PCM why it does not effect other things?
Thanks.

I didn't notice any damage or corrosion in wiring unless you mean I have to check the whole wiring of the car ! Any way I will take it to someone expert in reprogramming the PCM and I hope it will solve the problem.
Thank you very much.
Sayed Ali