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Old 10-14-2019, 06:01 AM   #1
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idle issues continue..

Hey guys, so my 01 gt has been making me crazy.. it runs great and idles good for I'm going to say around 30 minutes. at lights and stop signs it comes down to a nice idle and chops how it should. after driving about 30 minutes and 15-20 miles it will either stay at 1000 rpm and wont come down or sometimes it will surge but it usually idles at about 1000. I've tried multiple iac valves none have changed anything and I've done multiple checks for vacuum leaks and cleaned the mass air. I took the car to a local mechanic not once but twice now and he cant seem to figure anything out I feel as though it will be a waste of my time bringing it back to him. The thing that's really annoying is that I have to drive it for so long just to get the problem to occur. I've fixed this issue on more then 1 2v now but this one has me STUMPED! Btw no check engine lights and it runs good otherwise, the car has just about 130k and nothing from the cold air to the combustion chamber is stock besides the heads which are ported and have aftermarket cams. Any suggestions besides what I have tried will be a huge help thank you.

'11 gt w/brembo package & fbo cammed 01 gt
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Old 10-14-2019, 11:46 AM   #2
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Have you checked for vacuum leaks while the engine is at operating temperature, and the idle is hanging at the high rpm's?

You must have a tune for the cams....
Who did the tuning?
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Old 10-14-2019, 11:58 AM   #3
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yes I looked for leaks while at operating temperature while it was hanging. I use the starting fluid method idk if anyone recommends a better way? and I got it dyno tuned back in April 2018 so it's been a little while but it got tuned by a reputable tuner. Kevin hamden at wicked motorsports tuned the car

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Old 10-14-2019, 12:12 PM   #4
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I think that I would talk to them about your current problem. Tell them that you have tried everything that you know of, and had a mechanic look at it as well.
Ask them if they could look at a data log, or possibly put it on the dyno, and see if they can diagnose what may be going on with the idle once the car has been driven for a while.
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Old 10-14-2019, 12:18 PM   #5
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One other thing.

What brand of throttle body are you using?
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Old 10-14-2019, 12:21 PM   #6
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it has the bbk 78mm throttle body and a victor jr. intake. just weird to me because I havent made any changes at all to the car since then. idk if hes going to want to do anything with the car because it's been almost a year and a half now since it got tuned just started happening recently

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Old 10-14-2019, 12:23 PM   #7
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btw I meant Kevin hand* not hamden lol

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Old 10-14-2019, 12:30 PM   #8
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Now I'm sort of suspicious about the known-to-be problematic BBK throttle body.

Yes. You would probably need to pay Wicked Motorsport to look at your car. It's likely that a shop like that has seen this problem before, and has all of the equipment to properly diagnose the problem.
Note that I said "likely". I have no experience with that shop...
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Old 10-14-2019, 12:43 PM   #9
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yeah but I've had this on my car going on 3 years now why now? I was thinking a tps issue? but it seems like your learning towards either a tune or tb issue

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Old 10-14-2019, 12:54 PM   #10
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Not necessarily. I'm just throwing out ideas.
Mechanical, and electrical, parts usually work great.... Right up to the moment that they stop working.

I suppose that it is possible that it could be a failing TPS. Has it been tested while the idle is hanging?
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Old 10-14-2019, 01:01 PM   #11
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I had an idle issue like that and I did one thing that finally worked. After iacs and maf cleans, new filters and even a seafoam, I just took the throttle body off and cleaned it in both sides. The back side is probably more gunked up than you think. After I cleaned it, I also reset my idle by letting it run without the iac amd adjust the idle set screw until the engine dies. Replug the iac and bobs your uncle. No issues since!

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Old 10-14-2019, 01:18 PM   #12
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hmm.. maybe I'll throw a new tps on it and if that doesnt work I'll pull the tb off and give it a good cleaning. the car has an egr delete so I would of thought that would keep it cleaner but I havent been as into modding and working on my 2v as much lately since I got the 5.0 so maybe I should pull some stuff apart and do some cleaning

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Old 10-14-2019, 01:37 PM   #13
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If you don't have a code for your tps, I wouldn't bother replacing it. You'd be surprised how gunked up that tb will get

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Old 10-14-2019, 01:38 PM   #14
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It can't hurt to eliminate the easy, relatively inexpensive, things.

You should be able to inspect the throttle body blade by opening the throttle and using a flashlight and a mirror to see if the backside is excessively dirty.

The strange thing about the symptoms that you describe, is that the idle only hangs after the car has been driven for a while. Like there is something malfunctioning after reaching a certain temperature.
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Old 10-14-2019, 01:53 PM   #15
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Right... youd think is have the problem right away or once it's at operating temperature but after a half hour it's been at operating temperature for quite a little while. also weird to me that the car isnt throwing codes. think no should try a tps or just clean out the tb?

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Old 10-14-2019, 02:09 PM   #16
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Like Fender said, the TPS should trigger a code.... But stranger things have happened

I'd first inspect the throttle body, and clean it if it is dirty.
If you are positive that there are no codes, disconnect the negative battery terminal for a while, and let the computer relearn the idle parameters, and see what happens.
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Old 10-14-2019, 02:32 PM   #17
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Most of all my Ford idle issues have been resolved by a thorough tb cleaning. If it's not vacuum related and the MAF isn't throwing codes, then it only ever comes down to iac and tb. You could also clean the iac with brake cleaner. I ordered a new one but ended up keeping my old one after it cleaned it up nicely.

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Old 10-14-2019, 03:11 PM   #18
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ok I'll pull the cold air off and peek in. I'll also put a scanner back on it and check again for codes. can also do an idle relearn as well and if that stuff doesnt check out I can email kevin at wicked and get his suggestions. I really appreciate all the info

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Old 10-17-2019, 05:52 PM   #19
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1 Getengine to operating temperature.
2 Disconnect IAC (Idle Air Control) Solenoid. If engine stalls, turn throttle-stop screw in one full turn and restart. Repeat as necessary until engine will idle with IAC unplugged.
3 Set idle using throttle stop. Idle speed will vary depending upon modifications made to the engine. Set to where you are comfortable with idle speed.
4 Set TPS (Throttle Position Sensor) anywhere from .96 to .98 volts. This is done by loosening the mounting screws, and lightly rotating TPS. If you cannot obtain the desired range, you may need to make the mounting holes slightly larger. This can be done by drilling them.
TPS wire colors to be probed are generally BLACK and GREEN wire or the GRAY/RED and GRAY/WHITE, depending on your vehicle.
5 Stop engine. Disconnect negative terminal battery cable for 15-20 minutes. You may wish to tap the brakes or turn the headlights on and off a few times as this will help to ensure that you have purged any remaining electrical current from the vehicle.
6 Reconnect IAC Solenoid
7 Reconnect battery cable to the negative terminal
8 Restart engine.
If problem persists, inspect for mass air meter problems and possible vacuum leaks.
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Old 10-20-2019, 12:28 PM   #20
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I thought there was no benefit or reason to manually set the tps on the 4.6 cars and only worked on pre 96 mustangs. I was always told you can set it but after you start the car the ecu resets it

'11 gt w/brembo package & fbo cammed 01 gt
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Old 10-28-2019, 09:03 PM   #21
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hey guys so update. I havent had much time at all lately so I haven't had much time to work on or drive the car but so far I've done a few things. pulled the throttle body off to clean it. it didnt look too bad actually but I cleaned it. I then noticed the throttle body gasket was all ripped up so I was happy I thought that was for sure my issue. Threw a new gasket on and put it back together with not any change at all in the idle. I tried between 2 different iacs and the ford oem one seems to work better but still not good. it just kinda sits there and surges/ idle like complete hell. At this point I'm not 100% what to look at next

I also did clean the maf at the beginning of this problem before coming on here.
'11 gt w/brembo package & fbo cammed 01 gt
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