I have a 97 Toyota Corolla with a rebuilt engine that is threatening to stall when it is idle. It has been at the mechanics for two weeks and he is still stumped as to why it feels like it will stall. Anyone have any ideas?
It is likely the idle speed is just too slow. The slow idle could be a dirty airflow sensor, or one of many other causes. I wonder if there is a way to turn up the idle speed.
I will assume that the mechanic has cleaned the throttle body and through the idle air passages. The next step is to make sure that the Throttle Position Sensor is adjusted correctly and the noone has misadjusted the throttle plate stop screw. If these are indeed okey, the next step is to see if the windings of the Idle Air Control valve measure the correct resistance. Also make sure there is DC power to the IAC. Then I would look to see if the Power Control Module is commanding the IAC to move (square wave pulses on the drive wires). If everything checks out but the IAC is nonop, you will probably have to replace the IAC.
Hope that helps.
Do not dismiss the idea that some type of problem has been built in because of the rebuild (much less but possibly a intake manifold sealing or EGR operation problem) or a installation/connection error, I have even seen parts get crushed during engine installation.
At times people say their car “is at the mechanic” when it really is with the guy next door, is your car really with a professional mechanic? he really should know everything I mention. With mechanics it is a matter of pride to be able to diagnosis and make your rebuilds run perfect. To have your customer resort to witing to a online Forum must be humiliating, unless you are a DIY’er just tring to help out, its OK for this level of experience to throw up their hands and say “can’t fix it”.