Another hanging idle question?

Brackemyre1 · Mar 11, 2010

I just did like i everyone said and took the IAC off and cleaned it out, and all that and after i put it all back together i drove it and the idle got a lot worse? it idles at about 1500 rpm now when before it idled at about 500 and when i shift it is really bad, it jumps up and drops to about 2500 and stays there. Any advice? Its much needed.

phantom09086 · Dec 1, 2010

mine is doing the same thing let me know if you fixed it

FMSGTS · Dec 1, 2010

when you installed the IAC, do you know what value was reading, they need to be .96-1.0 volts. Check your service manual. Auto Zone sells the the manuals for $12.95 ..

phantom09086 · Dec 1, 2010

if you talking about the tPS it was at .98

justi88 · Dec 2, 2010

i also have that hanging problem and everyone says its the IAC... everytime i push the clutch the rpms go up to 2000 almost and then goes back down, you can find a new one on rockauto.com for 50$.. thats what im getting

phantom09086 · Dec 3, 2010

ok i am gonna check the site out, you ever order from them before

CC'S95GT · Dec 3, 2010

I'm also having the hanging idle issue.
I got a new IAC and it got waaay worse. so I put the old one back on till I could mess with it more.
I only have the hanging idle prob in the winter. Warm weather= no probs.
I've noticed if I shut the engine off once it's up to temp, then restart the idle stays right where it's supposed to be for the rest of the day.
Also my old IAC had the RTV plug removed and under it was an allen screw.
Whether it was messed with IDK. But if your going to buy a new one anyway why not learn something. just count the # of turns in and out just incase you need to put it back.

justi88 · Dec 3, 2010

CC'S95GT said:
I'm also having the hanging idle issue.
I got a new IAC and it got waaay worse. so I put the old one back on till I could mess with it more.
I only have the hanging idle prob in the winter. Warm weather= no probs.
I've noticed if I shut the engine off once it's up to temp, then restart the idle stays right where it's supposed to be for the rest of the day.
Also my old IAC had the RTV plug removed and under it was an allen screw.
Whether it was messed with IDK. But if your going to buy a new one anyway why not learn something. just count the # of turns in and out just incase you need to put it back.

What do you mean by counting the # of turns?? Right now i have a bronco IAC and got a little better but the problem is still there... to the OP i haven't bought from rockauto yet but my friend has and they have good prices and really fast shipping my friend got his things like in 4-5 days and we live in south america...

CC'S95GT · Dec 3, 2010

on the end of the IAC there is a little dab of RTV.
It covers the adjustment screw.
If you decide to mess withit, just count the number of rotations the allen screw is turned.

justi88 · Dec 3, 2010

and by moving this i will fix the hanging idle??

CC'S95GT · Dec 3, 2010

I don't know

Dr Fildo · Dec 4, 2010

+1 for the hanging idle issue. I have the AOD, but mine happens for a few seconds when I accerlerate and quickly step on the brake. The car keeps pushing for a second or 2 like I'm stepping on the brake and the gas at the same time.

I'm going to assume that if the little screw on the IAC was never turned (still covered by the RTV, then something else must be causing the problem.

I had the same problem on an '88 camaro that I owned (yes, I owned a Camaro, but I've been Rehabilitated since '95), and was told that the problem was the TPS, although I never tried to fix it. Not the same car, computer, or anything, I know.

Besides the voltage test that Phantom09086 did, has anyone checked more into the TPS?

Addermk2 · Dec 4, 2010

the issue is not in the TPS. Its usually due to people fucking with the idle set screw on the side of the TB, or disconnecting the battery and not performing the proper base idle proceedures after its reconnected.

So heres what you do.
Search for vac leaks... ensure that you have NONE!!!! make sur you check the hoses under the manifold, they are notorious for going bad.

start the car and allow it to get to full operating temp.
adjust your idle set screw in a few turns (like you are raising the idle)
start the car (it should be idling high)
Unplug the IAC (the car should NOT stall)
slowly lower the rpm's by loosening the idle set screw. You want the idle with the IAC unplugged to be around 675 rpms.
tighten the lock nut on the idle screw (and dont touch it again)
shut off the car and reconnect the IAC
disconnect the battery for about 20 minutes to clear the KAM, also step on the brakes a few times to kill any residual power left in the system.

This should fix your issue. If you are still having idle problems, suspect that you have not found all of your vac leaks, if any are present, OR your O2 sensors could be bad.

justi88 · Dec 4, 2010

mmm ok im going to do this and see what happens

phantom09086 · Dec 4, 2010

Me too I will try it also, when the weather clears. Ill post if the problem gets fixed

95-stang · Dec 5, 2010

This has worked for me, but if your running a non stock cam and auto trans 675rpm might not be enough so raise it a little.

phantom09086 · Dec 5, 2010

ok tried it today and it worked. thanks addermk2

Addermk2 · Dec 5, 2010

95-stang said:
This has worked for me, but if your running a non stock cam and auto trans 675rpm might not be enough so raise it a little.

no, you dont ever change it. If you run an aftermarket cam... you TUNE the car.

95-stang · Dec 5, 2010

I have had the car tuned, a guy i know on EECTuning wrote me a very good tune for my Q\H and set the idle about 900.

95-stang · Dec 5, 2010

Plus when i did a search a long time back nearly everywhere mentioned this, and i'm not saying your wrong or they are right btw.

It seems that many people have trouble with the way their 5.0 Mustang idles. Symptoms are usually a stumbling or rough idle which may be the result of modifications, or any number of other factors that may contribute to the problem. Clogged Emissions Gas Recirculation (EGR) Valves or Idle Air Bypass (IAB) solenoids are often to blame. A bad Throttle Position Sensor (TPS) will cause the engine to "hunt" for a proper idle setting. If you are experiencing idle problems first check the IAB. If it has large amounts of carbon deposits in it you may need to clean it using regular carburetor cleaner. You will have to remove it to do this, DO NOT clean it while it is on the car! If you have checked to make sure that your EGR, IAB, and TPS are clean and properly set and you are still experiencing problems try the following:
1. Clear the EEC-IV's idle memory by disconnecting the battery for 20+ minutes.
2. Disconnect the Idle air bypass solonoid
3. Reconnect battery
4. Start engine and set idle speed to desired RPM with stop screw on throttle body (900 rpm works great with E303 or larger cam)
5. Turn off engine and reconnect the air bypass solenoid*Optional -- set TPS to 0.90 - 0.95 volts (Do not exceed 1.0 volts MAKE SURE!) Use a digital volt meter!
6. Start engine and let it idle for 2 minutes with no accessories on.
7. Turn off engine for two minutes
8. Start engine again and run for 2 minutes with every accessory turned on.
9. Turn engine off again. Your computer should have now re-learned the new idle settings. This procedure assumes that you have a clean IAB valve. If it is carboned up then you may need to remove it and clean it with carburetor cleaner.