Ford Mustang Forums banner

1 - 20 of 30 Posts

·
Registered
Joined
·
443 Posts
Discussion Starter #1
I know this has come up before with the high Idle, it is now happening to me...When I come to a stop the Idle will hang at about 1500, If I tap the throttle it comes down, but will go back up and down..What do I check?? Thanks Dan
 

·
Registered
Joined
·
468 Posts
Check the IAC valve
 

·
Registered
Joined
·
155 Posts
Clean the IAC (idle air control) Take it off by removing 2 bolt's then clean the gunck out with a q-tip, carb cleaner and or compressed air.
 

·
Registered
Joined
·
310 Posts
IAC and TPS

If cleaning the IAC as suggeted by the other posters does not work, you may want to clean the TPS contacts and puting a small amount of dielectric grease on the pins.
 

·
Registered
Joined
·
32 Posts
I had the same problem with mine. Everytime I would drive anywhere at an extended amount of time at a high speed such as on an interstate, or just stuck in gridlock. My idle would go up to about 2K and sit there, if I tapped the gas it would come back down. I think Ford replaced my IAC 3 times, but it never went away. We finally figured the problem was coming from my WMS CAI. Somehow the sharp curve in the CAI was throwing off the signal to my MAF. I installed a UPR Power Pipe and a K&N big mouth filter, and I have had no more problems.
 

·
Registered
Joined
·
12 Posts
u know my car does that stuff too...only now it runs worse...(and its a 5.0) whats a WMS CAI??? and whats the upr power pipe?? an aftermarket intake??
 

·
Registered
Joined
·
369 Posts
Mine has the same exact problem. Ive replaced the TPS,IAC,PCV and still does it. :mad:
I might replace the throttle cable to see if that is the problem.
 

·
Registered
Joined
·
3,540 Posts
I've had that problem, and like most of you, replaced everything and still no fix.

I'm not smart about this stuff like most of you, and don't do my own work. Jake Lamotta does the work. But it's hard to duplicate always when I want someone to work on car.

But this is what I learned. On my car, the hanging idle only occured in hot humid weather. When it is hot weather, the car runs richer, the IAC tries to lean by injecting air, and idle increases. Sometimes I could knock it off, some times not. I solved this by lowering base FP slightly. No doubt the problem is caused by my Pro M 80 being slightly off calibration at idle. We have checked and reset slightly the idle MAF voltage. (I have adjustable Pro M) A MAFterburner would probably solve problem if I knew how to use one, and/or had wide band.
 

·
Registered
Joined
·
3,540 Posts
BTW...In order to eliminate as many potential problems as I could, I don't use an oiled K&N air filter. I just use the non oiled Pro M filter that looks just like a K&N without oil.

I believe (and Pro M does also) some of these idle problems are caused by oil being sucked onto MAF wires (especially on blown applications). It's also, IMHO, very difficult to clean and reoil like the factory job.
 

·
Registered
Joined
·
276 Posts
Rookie question,sorry! Where is the IAC actually located on these Cobras? thanks
 

·
Registered
Joined
·
811 Posts
Ralph Greene said:
<snip>No doubt the problem is caused by my Pro M 80 being slightly off calibration at idle. We have checked and reset slightly the idle MAF voltage. (I have adjustable Pro M) A MAFterburner would probably solve problem if I knew how to use one, and/or had wide band.
Hey Ralph,

Three quick points:

1. If the MAF curve is off at low-flow rates, the MAFterburner can easily fix it. This procedure can even be performed with the meter still on the vehicle.

2. If you can navigate this message board, you can use the MAFterburner tuning software.

3. You DO NOT need a wideband to do closed-loop tuning for idle and part-throttle driveability. All you need is an OBD-II scanner like Autotap. In essence all you need to do is monitor LTFTs, STFTs, and engine speed.

MJ
 

·
Registered
Joined
·
783 Posts
Did you ever resolve this issue? I'm having the same problem.

I dont have any mods on my car to speak of, so I can't blame in on a CAI or aftermarket chip or anything.. I've done all the checks on the TPS, and IAC, set my TPS voltage to .99, cleaned all the crap out of the IAC, cleaned my throttle body, checked for vacuum leaks. I'm at a serious loss here.

Could it be the fuel injectors? I read in one post somewhere that someone had a problem like this and it turned out to be a stuck injector..

I'd really like to figure this out, and it seems so would alot of other folks. I work with a guy that has a 98 Cobra also, and his does the same exact thing.

-Ronald
 

·
Registered
Joined
·
10 Posts
I had the same problem many of you have about a year ago (car also had slow decline of rpm's), except my car was stock except for a cat back, and k&n. I kept bringing it back to the dealer , they changed the tps twice changed the tps voltage, changed the imrc under the intake, I cleaned the iac valve. But no luck. Finally I told the service adviser to change the throttle body, after a little pushing they replaced it. The car has ran perfect for the last year. I think the butterflies were not closing far enough.

hopefully this helps some of you, it was a frustrating problem.
 

·
Registered
Joined
·
783 Posts
knrs88 said:
I had the same problem many of you have about a year ago (car also had slow decline of rpm's), except my car was stock except for a cat back, and k&n. I kept bringing it back to the dealer , they changed the tps twice changed the tps voltage, changed the imrc under the intake, I cleaned the iac valve. But no luck. Finally I told the service adviser to change the throttle body, after a little pushing they replaced it. The car has ran perfect for the last year. I think the butterflies were not closing far enough.

hopefully this helps some of you, it was a frustrating problem.
I'm curious now, I wonder if perhaps the throttle body gasket was not completely intact allowing air to seep in? I'm picking up a new TB Gasket today after work (its like 4 bucks.. BFD), then I'll pull my Throttle Body give it a thorough cleaning and put it back with the new gasket and see if that works..

Its ridiculous, this problem seems to be very prominent, but know one really knows what to do about it.. :(
 

·
Registered
Joined
·
10 Posts
smurph98gt said:
I'm curious now, I wonder if perhaps the throttle body gasket was not completely intact allowing air to seep in? I'm picking up a new TB Gasket today after work (its like 4 bucks.. BFD), then I'll pull my Throttle Body give it a thorough cleaning and put it back with the new gasket and see if that works..

Its ridiculous, this problem seems to be very prominent, but know one really knows what to do about it.. :(
If you spray some throttle body cleaner around the gasket area of the TB, and the car car starts to misfire like spraying it directly in the TB, you would determine if you have a gasket leak.

but then again the gasket is so cheap , it could not hurt to try.

best thing to do would be swap the throttle body with somebody else, who has a 96 to 98 Cobra ( if you know someone with one )since it is so easy to remove. I would let you borrow mine, but Cali is a little far of a drive for ya.
 

·
Registered
Joined
·
369 Posts
I still have the problem.
I may try to get another gasket. If that doesnt work, time to get a new TB I guess. :(
 

·
Registered
Joined
·
783 Posts
colt .45 said:
I still have the problem.
I may try to get another gasket. If that doesnt work, time to get a new TB I guess. :(
Well, if you're going to get a new Throttle Body, order it from Fordparts.com, it was like $115 there was opposed to the dealerships 200 something. :|
 

·
Registered
Joined
·
285 Posts
I too, am having this problem.

I found that if I unplug the IAC, the idle is fine.

I've replaced thses things: IAC several times, TB, TPS. No CE light from high idle.

What's the deal? Maybe a stuck fuel injector?

Jason
 
1 - 20 of 30 Posts
Top