High cold idle... I think its the ECU

[ZenkaiRacerDsM]

My car idles at 2500 when its cold, then as it warms it bounces around 2000, then when its warmed all the way it idles just fine. So far Ive replaced the ISC with a unit from crebotech. Didnt do a damn thing. Took the throttle body off and cleaned the shit out of it. Didnt do anything, Just today I took the fast idle valve off of the throttle body and cleaned the crap out of it. Still nothing. Im thinking its the ECU... what do you guys think? Tommarow if Im not lazy Im replacing the fast idle valve with one off a 98.

 

[talon1979]

It is normal for the car to idle at a higher rpm when the motor is cold, especially if it is really cold outside. As the car gets warmer the RPM's at idle will drop.

 

[ZenkaiRacerDsM]

Yes but 2500 is excesive and it bounces once it drops to 2000. Its not normal.

 

[crankbender]

Don't jump at this thing like crazy man...

if you are idling high it is usually just 1 thing...too much air is getting past the TB. First try and screw the BISS in. Then try blocking off the egr. If you still suspect the ISC (I don't but hey) pull it and have a friend turn the key on and off while you apply LIGHT pressure to the top of the ISC. it should move in and out smoothly. my car will sometimes idle that high untill it warms up.

Your coolant lines arn't blocked are they? this will cause the bouncing (otherwise known as idle surge). make sure they are flowing and that the coolant is all the way full. Are you having cooling problems?

Idle surge is caused by the ecu seeing too high an idle when the car is warm so it cuts the fuel. as soon as the idle comes down it gives fuel back (and since the problem is still there) the idle immediately rises again. The ECU rinses and repeats.

 

[Enigma_Man]

That's how mine's always behaved, it starts at around 2500, and then slowly decreases, though it doesn't bounce around.

Try an intake leak test.

-Jesse

 

[ZenkaiRacerDsM]

My coolant lines arent blocked off. My EGR isnt hooked up but the valve itself is still there. Could that be it? Does it need a block off plate? It shouldnt be the ISC because I just replaced it. The BISS is set perfectly for a warm idle.

 

[talon1979]

It sounds like you are suffering from idle surge. I would search for old/cracked, or disconnected vacuum lines.

 

[ZenkaiRacerDsM]

All of the vac lines that are supposed to go into the throttle body are blocked off.

 

[crankbender]

If it were a vacume line it wouldn't fix itself after a few mins.

Try a blockoff plate for the EGR first it is fast and easy. then get back .