Very High Idle Problem

Gr0und_Fault · Oct 19, 2006

Hello, I have a 95 manual trans v6. I've had a high idle problem for a while, and over time it keeps getting worse, and worse. About a year ago the high idle was around 1500rpm. I have cleaned the maf, iac, throttle body etc. Over time the idle became higher and higher to around 2800rpm with out me changing anything. I took the IAC back off yesterday and cleaned it with carb cleaner again and put it back on, now my idle has raised to around 3k - 3.2k rpm. I tested the resistance on the IAC as the Chiltons manual says to do and everything seems fine that way. I went to the junk yard to check out the internals of the IAC on other 3.8L and they all seem to let out the same amout of "idle air" when I physically blow air through them. Is there any other ways to test to see if the IAC is functioning properly? Can I hook up a 12V power supply and see if the solenoid shifts? Any help would be great.

Gr0und_Fault · Oct 19, 2006

This idle is seen as soon as I start the vehicle, and is a constant 3k rpm whenever I push the clutch all the way in while driving/stopping. Just thought I'd add that before someone asks.

Gr0und_Fault · Oct 19, 2006

My car also idles the same when I have the IAC disconnected as well.

Gr0und_Fault · Oct 19, 2006

Just checked the TPS voltage and I got .776 volts. I know I should be around .95 volts, but this voltage reading shouldn't be causing this problem, right? I read on here that WOT is supposed to be around 4.5 - 5V so me having a higher voltage than what I currently have would actually make me idle even higher, right?

Chythar · Oct 19, 2006

The TPS on our year cars doen't need to be reset. The computer reads the idle value and uses that as its base value. So, even if you could adjust it to .95, it would have no effect.

Your IAC has simply failed. It's a common problem, just go buy a new one.

Gr0und_Fault · Oct 19, 2006

Thanks for the quick response. I was hoping there was another way to test the IAC other than the way they chiltons manual tells you to. I am unemployed right now and can't afford to go around buying random parts seeing if the will make my car work or not. Looks like I'm going to have to though.......

Gr0und_Fault · Oct 20, 2006

Ok, just bought a new IAC and put it on. Started my car up and there is no change at all in the idle speed.

Gr0und_Fault · Oct 20, 2006

I am assuming now at this point then that I have a vacuum leak. I have a pressure/vacuum gauge that I can check the vacuum with no problem but I just need to know where I should check the vacuum at and the value that it should be at. Once I verify that I actually do have a vacuum leak, then I will search for the leak. Otherwise finding a vacuum leak will be extremely hard to find!

Gr0und_Fault · Oct 21, 2006

Replaced a couple of broken/rotted vacuum hoses that I have found and there is no change. I pulled out the PCV valve and checked to make sure that works fine and it does. I also checked for vacuum where the PCV valve is and I got a lot of vacuum there so it seems that I don't have a vacuum leak. I haven't used my vacuum gauge because I can't find it, but it feels like a really good amount of vacuum at that point. I'm stuck on this one guys.............

Gr0und_Fault · Oct 24, 2006

No other ideas anyone?

Gr0und_Fault · Oct 28, 2006

*bump* for help?

MustangLX-5.0 · Nov 11, 2006

Are you still having this issue or did you get it taken care of? If you still have this problem post a reply.I may know what the problem is.

Gr0und_Fault · Dec 5, 2006

Yes, I am still having this issue. The car has just been sitting around since the last time I posted on this thread. I just went outside to jump the car to recharge the battery because of the cold weather and it is still having the same issue with the high idle. If you believe you know what my problem may be, please help! Trust me, the high idle is very annoying!

the98stang · Dec 5, 2006

Gr0und_Fault said:
Yes, I am still having this issue. The car has just been sitting around since the last time I posted on this thread. I just went outside to jump the car to recharge the battery because of the cold weather and it is still having the same issue with the high idle. If you believe you know what my problem may be, please help! Trust me, the high idle is very annoying!

A steady high idle will not be caused by the IAC. And you proved that by getting a new one installed. If you have a vaccume leak, the idle will be more jumpy, not steady. If you have a STEADY high idle, the problem is the TPS. I would get a motorcraft TPS, adjust it to the correct voltage, and see if that fixes the problem.

Gr0und_Fault · Dec 5, 2006

the98stang said:
A steady high idle will not be caused by the IAC. And you proved that by getting a new one installed. If you have a vaccume leak, the idle will be more jumpy, not steady. If you have a STEADY high idle, the problem is the TPS. I would get a motorcraft TPS, adjust it to the correct voltage, and see if that fixes the problem.

Thanks for the quick response. Wouldn't a bad TPS throw a error code though? And I already checked the idle voltage with was I believe .776V at the TPS. Since the car responds to me giving more/less gas when I push in the pedal, doesn't that rule out the TPS being bad? Also I thought we didn't have to adjust the TPS on 95' as
Chythar has stated earlier in this thread.

jonjonjonjon · Dec 6, 2006

Not to hijack your thread, but send me a PM if you get the problem figured out. I'm having similar problem, but mine idles around 2000. I want to try to clean the IAF since a new one is pretty expensive. Did you use carb cleaner or brake cleaner? (Someone told me brake cleaner is ok but I dont like the thought of using it there).

Gr0und_Fault · Dec 7, 2006

jonjonjonjon said:
Not to hijack your thread, but send me a PM if you get the problem figured out. I'm having similar problem, but mine idles around 2000. I want to try to clean the IAF since a new one is pretty expensive. Did you use carb cleaner or brake cleaner? (Someone told me brake cleaner is ok but I dont like the thought of using it there).

Haven't fixed the problem yet. Still waiting on a response from 2 people if possible. Once the problem is fixed, I will post what I did to fix it. Oh yeah, and I used carb cleaner to clean my IAC, dunno about the IAF though.

Gr0und_Fault · Dec 14, 2006

*bump* for help

Gr0und_Fault · Dec 30, 2006

*bump* again for help

Gr0und_Fault · Jan 3, 2007

Dunno if this has anything to do with the problem, but the oil pressure and engine temp gauges seem broken. They are pinned to the left of the instrument cluster and the oil pressure one moves just a little every blue moon. Here is a vid of my high idle rpm's and instrument cluster failure at start up.

http://s10.photobucket.com/albums/a133/whiteboyrick/Mustang/?action=view&current=SSPX0071.flv

Very High Idle Problem

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