joshjwc9
Active Member
Is the car tuned in any way? There are several idle dashpots that may be corrupt/incorrect. A good tuner can fix a hanging idle in less than 5 minutes.
2003 Gt Engine Failure
- Thread starter Jinx
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It has a custom diablo tune on it, and has for the past 9 years with no issue. Unfortunately with the weather today, I probably won't get the chance to do anything since I don't have a garage or a carport.
OK as per the suggestion by wmburns I did the reset when the rain let up. I set the idle with the IAC unplugged to where the engine would just barely idle. At this point there was a hairline gap between the stop screw and the throttle plate arm. So the TP was completely closed. After finishing the reset car idles great at no load and at full load.
So I take it for a drive. Problem still persist of climbing RPMs in any gear at any speed when clutch is depressed and car is in neutral. RPMs will only drop from 2500 to 750 once care has reached complete stop for 3 seconds. I also want to note that on a flat stretch of open highway I can have the car in 5th gear and my foot completely off the accelerator and the engine will retain an RPM of 1400 and a cruising speed of 47 MPH. It held like this for 2.5 miles until I had to break due to upcoming intersection.
So I take it for a drive. Problem still persist of climbing RPMs in any gear at any speed when clutch is depressed and car is in neutral. RPMs will only drop from 2500 to 750 once care has reached complete stop for 3 seconds. I also want to note that on a flat stretch of open highway I can have the car in 5th gear and my foot completely off the accelerator and the engine will retain an RPM of 1400 and a cruising speed of 47 MPH. It held like this for 2.5 miles until I had to break due to upcoming intersection.
runningONfumes
Member
WTF?!?! It really maintained 47 mph for 2.5 miles. That's insane. Mine would maintain cruising highway speeds like that but only untill I tapped the brakes just enough for the light brake lights to come on. But my problems were due to a faulty torque converter, being mine is auto.
I wish you luck getting this under wraps!
Yes. It truly did. I even had it in a vacant parking lot in first gear and the car just cruised on its own, even after tapping the break. It would stop the behavior only if I came to a complete stop, in neutral, for 3 seconds to the the RPMs drop to idle.
wmburns
SN Certified Technician
^^^^^this is a clue to the problem. The idle screw needs to be backed off even more but all physical adjustment is gone.
The fact the motor is still able to run at all tells me there is air entering from someplace else. The trick is going to be finding where.
Don't you have an ODB2 scanner? Post the IAC duty percent at idle and under load. Also post the LTFT bank 1/2 at idle and under part load.
Here's some information on how to perform a DIY smoke test from allfordmustangs. I really think a vacuum leak is what the root problem is.
/forums/4-6l-tech/49661-your-mustang-stumbling-dieing-idle-idling-rough-16.html#post2942011
not sure why the idle stop screw would need to be backed off further, since the TB arm can not physically go past the point it was at when I set it the last time?? I have a Predator tuner and am not sure if I know if it can be used to get the information you suggested. Thanks for the link as well, but it's not working.
Called the other Ford service center today. It's an extra 20 mile drive, but they have set me an appointment for Wed at 8:30. We'll see what they have to say.
Mattstang04
15 Year Member
Did you try shooting some carb cleaner around the intake and listening for the engine to rev higher? It will work if the vacuum leak is sucking but not if it is blowing. Worth a shot though.
1987stangman
Member
- Jul 12, 2006
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I might as well throw this out there. I had a guy bring a Ranger with a V6 to my shop with nearly the same exact issue. Changed out IAC and eventually TPS, no change. Idle would hit 1k at stop lights. No codes at all. If your tuner or code reader will let you look at live data while you drive and the problem happens watch TPS value and see how it behaves. I ended up spraying the TPS connector plug out on both ends and even tho it really looked OK it ws dirty enough to cause this issue. Not saying this is your problem, but it might be worth looking at.
While there has been good advice in here, I have not had much time to implement many of them. This is due to the fact that I don't have a garage or covered car port, and it has been raining here the past 4 days (almost 11 inches total). The rivers are flooded and every time I thought I would have a moment it would rain. So I am just going to wait until Wed. when I can get it to the service center.
Thanks to all, and I will let you know what they find.
Thanks to all, and I will let you know what they find.
sneaky98gt
10 Year Member
He's saying that the throttle body blade itself needs to back down some more, in essence. If the IAC is disconnected, and the TB is completely closed (as indicated by the fact that the screw isn't even touching), then no air should be entering the engine and it shouldn't run at all. If it will still run at 500 RPM with everything 'closed', then you have 500 RPM worth of air entering the engine from somewhere else. i.e. vacuum leak.
My thoughts, too. The car is idling from a vacuum leak, and when air is allowed in through the IAC and TB, the RPM spike.
Rusty67
Dirt-Old 20+Year Member
Service center has had the car for 2 weeks and still don't know what is wrong. They have informed me they have put in a "call request" with a "Ford Engineer" from whatever mystical lands they reside. Apparently my problem is more serious than an oil change or a tire rotation. 
Rusty67
Dirt-Old 20+Year Member
Does the service center have a Ford Master Tech on site ? If not that may be why they are putting in the call. Hope they find something soon.
Probably not, this Town ain't big enough. They used to have some really good mechanics, that knew their stuff and now it seems like it's all run by high school kids with little or no experience.
![funny-pictures-pony-mechanic[1].jpg](/cdn-cgi/image/format=auto,quality=80,sharpen=1/https://stangnet.com/mustang-forums/attachments/funny-pictures-pony-mechanic-1-jpg.81935/ "funny-pictures-pony-mechanic[1].jpg")
joshjwc9
Active Member
I don't know where you found this, but this picture is golden and will be filed away on my computer.
I still think it is alternator related..although yours looks practically new.
Also, I would have put the stock tune and ditched the Diablo tune before you sent it to Ford.
I used to have a hanging idle or rising idle upwards to 2k at a stop, but the combination of my tuner adjusting a couple settings in it and my alternator fixed it perfectly.
I still think it is alternator related..although yours looks practically new.
Also, I would have put the stock tune and ditched the Diablo tune before you sent it to Ford.
I used to have a hanging idle or rising idle upwards to 2k at a stop, but the combination of my tuner adjusting a couple settings in it and my alternator fixed it perfectly.
Just heard from the service center. Even with a full diagnostics, a temporary replacements of parts to trouble shoot, and advice from Ford engineering, they still can not figure out why my car is having the high speed RPM hanging issue. They are thinking it may be the PCM itself. They are going to let me take posession of the car until they hear back from the engineering. FML
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