end of my high idle rope

[long tall eta]

damn, adjusted the valves and put new plugs in her and the idle went from 1200 to 1700. wtf. this is driveing me nuts. everything under the hood seems to be good. could a bad o2 sensor cause this high idle????
or what about a bad maf.
question, everybody says intake leak, now when i pop off the oil fill cap or pull the dip stick while running, the idle drops to around 500 and very rough. removeing those creates an intake leak right? so what other intake leaks would cause a high idle?

[jlevie]

Causes of a high idle include:

1) Intake leaks. You can try to find them visually or with carb cleaner, but the only sure way is to have a shop run a smoke test.

2) A sticky or defective ICV. The ICV can be removed and cleaned with carb cleaner until the van moves freely.

3) A bad or misadjusted TPS or a misadjusted throttle stop.

4) A binding throttle body or accelerator cable. If this is happening pushing the throttle arm closed will drop the idle.

5) A bad Engine Coolant Temp sensor. A resistance check of the sensor will tell if it is bad.

6) On an ETA the Idle Control Module could be bad. The DME is a rare possibility on later cars

To solve this problem do (1) and (2) first. Once it has been proved that there are no intake leaks check the operation of the idle switch in the TPS with an ohmmeter and replace the TPS if either the idle or WOT switch isn't working. If the O2 sensor on the car has over 100K, replace it also.

If the idle is still high and the previous items have been addressed adjust the idle stop and TPS by:

With the engine at normal operating temperature disconnect the ICV and adjust the throttle stop for an idle of 950rpm. Then shut down the engine and adjust the TPS so that the idle switch closes when the throttle arm is 0.030-0.060" off the stop screw. Reconnect the ICV and turn the ignition on. If the ICV isn't buzzing it, the ICV is bad, there's a problem in the wiring, or the ICM or DME is bad. Otherwise crank the engine and the idle should stabilize at 750rpm.

It is possible that someone has fiddled with the AFM or that the van is sticking In which case (after exhausting the other fixes) swapping in a known good AFM is indicated.

I can't emphasize enough how important (1) is. Engines with electronic fuel injection are extremely sensitive to intake leaks and the only way to conclusively find those is with a smoke test.

[long tall eta]

Causes of a high idle include:

1) Intake leaks. You can try to find them visually or with carb cleaner, but the only sure way is to have a shop run a smoke test.

2) A sticky or defective ICV. The ICV can be removed and cleaned with carb cleaner until the van moves freely.

3) A bad or misadjusted TPS or a misadjusted throttle stop.

4) A binding throttle body or accelerator cable. If this is happening pushing the throttle arm closed will drop the idle.

5) A bad Engine Coolant Temp sensor. A resistance check of the sensor will tell if it is bad.

6) On an ETA the Idle Control Module could be bad. The DME is a rare possibility on later cars

To solve this problem do (1) and (2) first. Once it has been proved that there are no intake leaks check the operation of the idle switch in the TPS with an ohmmeter and replace the TPS if either the idle or WOT switch isn't working. If the O2 sensor on the car has over 100K, replace it also.

If the idle is still high and the previous items have been addressed adjust the idle stop and TPS by:

With the engine at normal operating temperature disconnect the ICV and adjust the throttle stop for an idle of 950rpm. Then shut down the engine and adjust the TPS so that the idle switch closes when the throttle arm is 0.030-0.060" off the stop screw. Reconnect the ICV and turn the ignition on. If the ICV isn't buzzing it, the ICV is bad, there's a problem in the wiring, or the ICM or DME is bad. Otherwise crank the engine and the idle should stabilize at 750rpm.

It is possible that someone has fiddled with the AFM or that the van is sticking In which case (after exhausting the other fixes) swapping in a known good AFM is indicated.

I can't emphasize enough how important (1) is. Engines with electronic fuel injection are extremely sensitive to intake leaks and the only way to conclusively find those is with a smoke test.

first off i want to thank you for helping both here and over on that other forum.
second, everything you have listed except the o2 sensor and the tps has bin checked or done. this is whats so frustrating. question, if i take the oil fill cap off the idle drops dramatically and the same with the dip stick and they both create vac leaks correct? so how would another intake leak create a high idle? shouldn't all intake leaks affect the engine the same? when i first start her up, she is at 1000 now and when fully warmed up 1700. the cts is only 2 months old. i just cant help feel its some how electrical. the other day the wife and i where out and when fully warm, shut her down and ran into a store for no more than 3 minutes, when i started her back up a perfect 750 for about 5 minutes then slowly back to 1700. i'm a shade tree mechanic and with no e30 specific shops around i might have to hoof it up to levant. 3 hour ride 1 way.

[jlevie]

A big leak, like when you pull the oil filler cap will cause the engine to bog down and run rough. Small leaks can cause it to run fast.

Have you had a smoke test run (and run properly)? That would mean plugging the exhaust and substituting an adapter for the AFM, introducing smoke through the adapter, and holding at least 2psi of smoke pressure in the intake for 15 or more minutes.

[long tall eta]

A big leak, like when you pull the oil filler cap will cause the engine to bog down and run rough. Small leaks can cause it to run fast.

Have you had a smoke test run (and run properly)? That would mean plugging the exhaust and substituting an adapter for the AFM, introducing smoke through the adapter, and holding at least 2psi of smoke pressure in the intake for 15 or more minutes.

the smoke test i had done did not look to be what you describe. only had a quick look at the set up but don't recall the afm being involved. they introduced the smoke through one of the hoses comming from the tb.

[jlevie]

A smoke test can be done that way, but it is best to test the system with all parts after the AFM intact. And it is essential that pressure be built up in the intake and held for a while. If there crank case leaks it takes a while for the smoke to work its way to those leaks.