Ever since i replaced my auto transmission about a week ago, the idle's been acting weird. Im not sure if its related to the transmission. It could be just a coincidence that its happening now after changing the transmission. This is whats happening... Sometimes the idle is at 500 and sometimes at 700, and other times slightly above 1000. This is what i noticed...the idle could be at 700 (which i think is the factory setting), if i turn the car off for a couple of mins and start it, it would idle at 500. And sometimes if i rev the engine and let go of the gas, the needle will go down and stop at just a little over 1000. Sometimes it would idle at 500 at the light. Basically its random like that between 500, 700 and 1000. A few times it has stalled on me when i first started the car in the morning. Other times it stalled when i turned the steering wheel all the way. Sometimes it just outright feels like its going to stall like when i am at the light. Also usually its a rough idle. The rpm wouldnt be stable, it would moving up and down between 500-900. Any idea whats going on? Ive changed the head gasket about a month ago so ive thoroughly cleaned the manifold and throttle body.
Have you checked the solenoid valve that purges the charcoal cannister that collects fuel tank vapour? They can get stuck open which can cause a bad idle as they are only meant to open once the engine is warmed up and the car is being driven above a certain speed. Also have you checked the operation of the Idle Air Control Valve and/or the output of the throttle position sensor?
Funny that you mentioned the purge canister. Just mins ago i noticed that its making a pulsating/tapping noise. When i disconnect it, the noise disappears. How can i make sure that it is operating properly? I just cleaned the IAC. It was black from carbon. Of course i also cleaned the housing for it thoroughly. Unfortunately, it didnt change the idle, its still the same. How exactly can i check the output of the TPS? Do i remove it and clean it like the IAC?
The purge cannister solenoid valve should be closed when the engine is at idle. You could disconnect it at each end and connect a vaccuum hand pump to one side and see if it holds vacuum this will tell you if it is leaking or not. There is a test procedure for the IAC from memory you take it out and turn the ignition on and it should go in and out a few times? I had a bad idle in my old VN and a new one fixed it but they are not cheap. TPS is a variable resistor which should have a min and max resistance and a certain amount of change per increment of rotation. I don't know what the figures are off hand, someone else may be able to post this information?
