My car idles at about 2000 and
i just patched up the vacuum leak and it still runs high. If i put tape partillaly over the idle air port in the throttle body to slow down the air flow will this hurt my engine. It would only be temperary until i find the cause to my high idle.

any thoughts?

-Dorian

I wouldn't do it-it could easily get sucked into the engine. Try disconnecting your battery for about 1 minute to clear the memory out of the ECM and then go for a drive. After the car has been driven enough to thoroughly warm it up, the ECM may relearn the idle. If it still idles too high, then you can start looking for other causes.

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Rod Schneider, Woodstock, Ga.
"You can't have too many toys!"
1988 Fiero GT
1966 Porsche 911
Van's RV-6 airplane-under construction

My initial thoughts... Covering the IAC hole isn't going to hurt the engine in the short term, It is always trying to achieve proper fueling based on readings from the o2. However, since covering the IAC brings the Idle down on your car, you know you don't have a vacuum leak. The IAC valve is either malfunctioning. Or, far more likley, your Throttle Position Sensor or Coolant Temperature Sensor have crapped out.

Now, this is important: The computer MAY NOT set a code even if the sensors have crapped out. The sensors can be inaccurate, but still be in range enough to not set a code.

In the long term, since the sensors are most likley to blame for what is wrong, the engine will most likley devour fuel and this shortens the lifespan of the engine by introducing more fuel into oil, and washing the oil off the cylinders. The piece of tape won't do much harm unless it gets sucked in, or jams up the IACV.

quote Originally posted by Fierobsessed: However, since covering the IAC brings the Idle down on your car, you know you don't have a vacuum leak.

Does it bring it down or kill the engine. If you have leaks and cover the oac port the engine will keep running. If you don't it should die.
If the engine is trying to idle correctly the ecm should be closing the iac all the way anyway if there is a leak.
I would think if it is not then it's sticking or not working right. But do try the above and remove power from the ecm to see if that helps.

[This message has been edited by Dodgerunner (edited 03-21-2008).]

If you completely cover the IAC port the engine should die immediately. If it does not then you still have a vacuum leak. An incorrectly adjusted "idle" screw can do it as well as a partially stuck open throttle plate due to dirt/grime. Has your "idle" screw been tampered with (the cover is missing)?

I put quotes around idle screw because it's actually a throttle plate adjusting screw. The ECM controls the idle through the IAC motor. The purpose of the screw is to set the minimum throttle plate opening so it does not get stuck in the bore by closing too far.

fix the proplem the right way first, bandaids dont fix engines.


if u come up to my shop i could smoke the engine and find your leaks fast, but i dont think you could get here fast enough. lol. try your local shops and see if theyll smoke the car for you, (evap leak detector)

Good info above. Just curious, have you done any work on that engine lately?

quote Originally posted by Hudini: If you completely cover the IAC port the engine should die immediately. If it does not then you still have a vacuum leak. An incorrectly adjusted "idle" screw can do it as well as a partially stuck open throttle plate due to dirt/grime. Has your "idle" screw been tampered with (the cover is missing)? I put quotes around idle screw because it's actually a throttle plate adjusting screw. The ECM controls the idle through the IAC motor. The purpose of the screw is to set the minimum throttle plate opening so it does not get stuck in the bore by closing too far.

If your idle set screw has been tampered with you will see a hole that has been drilled above the screw and the screw itself will be exposed. You should never have to adjust it.

If you cant find any vacuum leaks check the IAC lines with a voltmeter to make sure the ECM is actually trying to adjust idle. A while back I had fixed all the vacuum leaks and it still had a high idle. I checked the IAC pins and only one side was getting a pulse. The ECM raises the voltage and sinks current with the other to move the stepper motor. I replaced the ECM and it still didnt work. The cause was one of the previous owners cut the power wire to the ECM and replaced the break with a smaller gauge wire that had corroded over the years. Thus, the ECM didnt have enough power to step the IAC so it was always too far open. Replacing the wire with proper gauge and crimping the connections properly fixed the problem.

i know i dont have a leak. I spent forever finding the leak in my egr but i fixed that. My engine will stall when i cover the idle air port. my sensor contacts are spotless. I dont think It will suck into my engine if i use a big enough piece of tape. Like I said it would only be temporary until i find the culprit

Some have posted a measurement from the edge of the opening to the butterfly but I think it's probably better to just do it by feel.
You can back the screw out until the butterfly start to feel like it's sticking when you push it shut and open it. Once you find that point you can adjust the screw so that it no longer sticks and add a 1/4 turn.

The other way I usually do it if I know I don't have any leaks is use Winaldl to adjust the screw so the IAC count reads around 35-40 counts when the engine it hot. That setting has worked well for me...