Idle issue

[Nightmare90gt]

I'm in need of help I have been troubleshooting this idle issue for a long time. My rpms like to stay around 1200. I have got forescan lite.

I have replaced the following
All vaccume line
Tps-voltage per forescan is .92
IAC-03/04 OEM one (planning supercharger swap soon)
Intake manifold gaskets
02 sensors (fronts only rears are off)
Air filter
Plugs and coils
One thing I have noticed on forescan at idle my fuel pump duty cycle goes from 80-114% constantly.
The car has 170k mile every sensor besides the following have been replaced.
Maf
Fuel injectors
Ccrm
Fpdm
Fps
Cam position sensor
Crank position sensor
Alternator
My tuner broke so I don't know if I can put another tune on it if I buy a new tuner.

Any help is appreciated

 

[98 svt]

Sounds IAC/TPS related to me.

 

[Nightmare90gt]

The two last one are with ac on.

 

[03cobra#2]

I would look at some new tuning options. You'll probably need to have someone re create the factory tune that you can drop back into the car then get another custom tune if tyou go sct Or just buy a Moates quarter horse system then you can change the tune that is in the car and data log.

 

[Nightmare90gt]

Would the computer be locked because of the tune on it? Would it would require me to need to get a new computer in order to put a new tune on it with the moates or sct

 

[03cobra#2]

Would the computer be locked because of the tune on it? Would it would require me to need to get a new computer in order to put a new tune on it with the moates or sct

Someone else can chime in but I believe even with a custom tune on there your cpu is not locked in any type of way.

 

[Nightmare90gt]

Someone else can chime in but I believe even with a custom tune on there your cpu is not locked in any type of way.

That would be great news.

 

[BlackStang00]

The ecu isn’t locked if you used an sct device.

Whenever I’ve logged with Forscan the fuel pump monitor pid has always come up at on or off, not a percentage. Perhaps I just have it set up differently but I don’t think it’s your problem. Have you checked all your bases? I see the desired rpm is less than 900 rpm’s so something is preventing it from settling down. Did you unplug the iac while it’s running? Have you verified the coolant temperature and iats are accurate?


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[cobracide]

TPS voltage is key on engine off. Shoot for .98v The throttle adjustment screw needs to be set so their is a very small gap. it's only like 2 1/2 turns from closed. @ .01" If the gap is too large, the idle will hang high. If it hangs still @ .98v reset the computer to re-learn.

 

[Nightmare90gt]

The ecu isn’t locked if you used an sct device.

Whenever I’ve logged with Forscan the fuel pump monitor pid has always come up at on or off, not a percentage. Perhaps I just have it set up differently but I don’t think it’s your problem. Have you checked all your bases? I see the desired rpm is less than 900 rpm’s so something is preventing it from settling down. Did you unplug the iac while it’s running? Have you verified the coolant temperature and iats are accurate?


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By bases what do you mean?

I have not unplugged the iac resently while it's running. I did before part of the reason I replaced it because the previous one seemed to be acting up.
Other than using forescan how would I verified coolant temp. Intake air is near ambient temp.

 

[Nightmare90gt]

TPS voltage is key on engine off. Shoot for .98v The throttle adjustment screw needs to be set so their is a very small gap. it's only like 2 1/2 turns from closed. @ .01" If the gap is too large, the idle will hang high. If it hangs still @ .98v reset the computer to re-learn.

Will check to see what the voltage is with key on eng off. The throttle is stock and also have had a accufab 58mm throttle body idle has been no change. The computer has been reset since the lower intake gaskets.

 

[BlackStang00]

What I meant was, have you checked things like compression and vacuum. And put a multimeter on the sensors to see what the voltage drop is or even a laser thermometer to verify coolant temp. I don’t know how long it was running in that log you posted but 140* is low.


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[Nightmare90gt]

What I meant was, have you checked things like compression and vacuum. And put a multimeter on the sensors to see what the voltage drop is or even a laser thermometer to verify coolant temp. I don’t know how long it was running in that log you posted but 140* is low.


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I just started it up after is was sitting for a little bit. Full temp put coolant at 195*.
Compression I haven't but the engine is still on a pretty fresh rebuild with only about 7k miles if that. I have been using forescan for voltage drops but hard to know what the values are suppose to be...lol

 

[Nightmare90gt]

Has anyone ever seen a car where the idle goes to 1200 when the the compressor kicks on. Most of the time it seems to be fine now once it warms up but acts up when the AC/heat is on.

 

[BlackStang00]

I wouldn’t rule out a vacuum leak or the tune.


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[DSG2003Mach1]

Did it ever idle correctly on the new motor? I changed compression (lowered it) and the idle would hunt around 1k-1200. Tuner had to make some changes and it idled like a champ

As far as tuning - you do NOT have to load a stock tune in order to retune. The device will save the current tune and label it as stock but doesn’t hurt anything.

Have you cleaned the maf with maf cleaner or even just unplug it?

 

[Nightmare90gt]

Does anyone know the size of the fuel pressure sensor o-rings I found that leaking

 

[Nightmare90gt]

Did it ever idle correctly on the new motor? I changed compression (lowered it) and the idle would hunt around 1k-1200. Tuner had to make some changes and it idled like a champ

As far as tuning - you do NOT have to load a stock tune in order to retune. The device will save the current tune and label it as stock but doesn’t hurt anything.

Have you cleaned the maf with maf cleaner or even just unplug it?

Yes the car idled perfect before I swapped from the 3650 to the t56. My compression is 11:1 so I went up .5.

I have cleaned the maf a few times.

 

[DSG2003Mach1]

Yes the car idled perfect before I swapped from the 3650 to the t56. My compression is 11:1 so I went up .5.

I have cleaned the maf a few times.

if the tuner has not made changes since the compression change I would send him a log. I dropped mine .5 and it all went to hell. I assumed it had to be mechanical but I was wrong. One tune revision later it idled like a champ

 

[Nightmare90gt]

if the tuner has not made changes since the compression change I would send him a log. I dropped mine .5 and it all went to hell. I assumed it had to be mechanical but I was wrong. One tune revision later it idled like a champ

I'm working on getting the stuff to tune it with the quarterhorse to take that out the equation. Thank you for the insight