Car won't idle right...help
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Le Mans Master
Joined: Mar 2013
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St. Jude Donor '14
Car won't idle right...help
Well brought car back to shop to get some tuning stuff done at idle. Unfortunately car didn't duplicate problem while I was there so it understandably it's limited in what could be done. Murphy's law of course on the way home voila it started acting up again. I'm opening it up to others for an opinion on what's the deal?
My guess is maybe this is a bad O2 sensor that when heated up big time it gives an inconsistent signal. I would think if that were the case it would do it at all times but normal loads (see video) it's fine. I'm open to suggestions...
Normal day-to-day driving local errands and whatnot...100% fine. The car holds a nice 14.7 +/- a few tenths. Long driving (e.g. over an hour plus of driving) and the idle decides to not want to play nice. Any thoughts? Video shows it perfectly.
Idle or extremely light throttle (to hold 1500rpms or less) it will run pig rich and stumble. Under any load (rev hold 2000rpms or higher) or normal driving at speed there's no issues.
Thoughts?
See video...
My guess is maybe this is a bad O2 sensor that when heated up big time it gives an inconsistent signal. I would think if that were the case it would do it at all times but normal loads (see video) it's fine. I'm open to suggestions...
Normal day-to-day driving local errands and whatnot...100% fine. The car holds a nice 14.7 +/- a few tenths. Long driving (e.g. over an hour plus of driving) and the idle decides to not want to play nice. Any thoughts? Video shows it perfectly.
Idle or extremely light throttle (to hold 1500rpms or less) it will run pig rich and stumble. Under any load (rev hold 2000rpms or higher) or normal driving at speed there's no issues.
Thoughts?
See video...
Thread Starter
Le Mans Master
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St. Jude Donor '14
Race Director
Joined: May 2004
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From: Raleigh, NC
St. Jude Donor '15
Yeah MAF doesn't matter in that case (I think you're still using it for IAT's, so that portion of it still matters, though I highly doubt that's the problem)
I'd replace O2's first
What do fuel trims look like? You should be able to see them on dash logic. I set up custom variables for total fuel trims bank 1 and total fuel trims bank 2 (short 1 + long 1) and (short 2 + long 2) to get a total for each bank
What else was done tune wise?
Any chance of an exhaust leak? Long shot but it doesn't take much to make O2 sensors go nuts which will making fueling go nuts..
Do you have HP Tuners? If you can send me a log I'll take a look and see if I notice anything
I'd replace O2's first
What do fuel trims look like? You should be able to see them on dash logic. I set up custom variables for total fuel trims bank 1 and total fuel trims bank 2 (short 1 + long 1) and (short 2 + long 2) to get a total for each bank
What else was done tune wise?
Any chance of an exhaust leak? Long shot but it doesn't take much to make O2 sensors go nuts which will making fueling go nuts..
Do you have HP Tuners? If you can send me a log I'll take a look and see if I notice anything
Last edited by schpenxel; Nov 20, 2015 at 01:44 PM.
Thread Starter
Le Mans Master
Joined: Mar 2013
Posts: 7,392
Likes: 137
From: Ahead of You :)
St. Jude Donor '14
Yeah MAF doesn't matter in that case (I think you're still using it for IAT's, so that portion of it still matters, though I highly doubt that's the problem)
I'd replace O2's first
What do fuel trims look like? You should be able to see them on dash logic. I set up custom variables for total fuel trims bank 1 and total fuel trims bank 2 (short 1 + long 1) and (short 2 + long 2) to get a total for each bank
What else was done tune wise?
Any chance of an exhaust leak? Long shot but it doesn't take much to make O2 sensors go nuts which will making fueling go nuts..
I'd replace O2's first
What do fuel trims look like? You should be able to see them on dash logic. I set up custom variables for total fuel trims bank 1 and total fuel trims bank 2 (short 1 + long 1) and (short 2 + long 2) to get a total for each bank
What else was done tune wise?
Any chance of an exhaust leak? Long shot but it doesn't take much to make O2 sensors go nuts which will making fueling go nuts..
Well I'm road tripping it in a few hours so I won't be able to really troubleshoot much until I get back. However, what am I setting up on the dashlogic to view I'm open to fiddling with it I'll have 3-4 hours of straight highway driving in a little bit.
EDIT: I don't have HP Tuners software
Last edited by Nosferatu; Nov 20, 2015 at 01:46 PM.
Race Director
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St. Jude Donor '15
Make a custom screen with
short term fuel trim 1, long term fuel trim 1, short term fuel trim 2 and long term fuel trim 2 all on one screen
If you can fit the wideband reading on the same screen then that'd be awesome too.
{4} {5} {6} {7} {whatever your wideband is}
short term fuel trim 1, long term fuel trim 1, short term fuel trim 2 and long term fuel trim 2 all on one screen
If you can fit the wideband reading on the same screen then that'd be awesome too.
{4} {5} {6} {7} {whatever your wideband is}
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Thread Starter
Le Mans Master
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St. Jude Donor '14
okay I made a screen as follows...
Short Term Bank 1/2
Long Term Bank 1/2
...all 4 in the heads up display
I then put AFR in the dic
Race Director
Joined: May 2004
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From: Raleigh, NC
St. Jude Donor '15
Good deal. I don't know if I can see the HUD from a video but if you can get an idea what the numbers are doing it's a start.
It's a guess at this point but hey, you've got a few hours of driving to do so might as well try and troubleshoot
It's a guess at this point but hey, you've got a few hours of driving to do so might as well try and troubleshoot
Thread Starter
Le Mans Master
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From: Ahead of You :)
St. Jude Donor '14
I don't know what to interpret from the short term fuel trim but didn't look any different from when before it was doing to after. An hour or so into drive it acted up. Hit a down pour of rain and problem fixed (cooling effect of water???) only for it act up after getting back to dry roads.
Drifting
Joined: Dec 2012
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From: O'Fallon IL
I would use the MAF cleaner on the IAT sensor wherever the location is in case there's some crust over the reading element. If you don't have an oil catch can there's a good chance of oil saturation if the sensor is on the intake.
Race Director
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From: Raleigh, NC
St. Jude Donor '15
Car isn't missing it drives fine under any load other than idle after sitting a while.
I don't know what to interpret from the short term fuel trim but didn't look any different from when before it was doing to after. An hour or so into drive it acted up. Hit a down pour of rain and problem fixed (cooling effect of water???) only for it act up after getting back to dry roads.
I don't know what to interpret from the short term fuel trim but didn't look any different from when before it was doing to after. An hour or so into drive it acted up. Hit a down pour of rain and problem fixed (cooling effect of water???) only for it act up after getting back to dry roads.
I was just curious to see if anything weird happened with either at the same time this issue happened. I.e. shoots to +20 or -20, something extreme like that. In a perfect world they'd be close to 0 all the time
Thread Starter
Le Mans Master
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St. Jude Donor '14
STFT will mostly always just bounce up and down around 0. LTFT are where major adjustments are stored.
I was just curious to see if anything weird happened with either at the same time this issue happened. I.e. shoots to +20 or -20, something extreme like that. In a perfect world they'd be close to 0 all the time
I was just curious to see if anything weird happened with either at the same time this issue happened. I.e. shoots to +20 or -20, something extreme like that. In a perfect world they'd be close to 0 all the time
Melting Slicks
Joined: Oct 2007
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This means your LTFT are turned off and the car is running closed loop with STFT only. If SD tuned you may be hitting a place in the map where it needs adjustment at low rpm. New 02s will not hurt to try
Race Director
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From: Raleigh, NC
St. Jude Donor '15
That sounds pretty normal though on the STFT's.. the 12% is a bit high but it's not enough for me to think that's the problem. In the real world, it happens.
In a perfect world they'd constantly go back and forth from a few percent under 0 to a few percent over zero.
Are they doing anything weird at the same time this issue happens?
Thread Starter
Le Mans Master
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From: Ahead of You :)
St. Jude Donor '14
Yeah tuner must have disabled long term fuel trims. Not too unusual so no big deal there
That sounds pretty normal though on the STFT's.. the 12% is a bit high but it's not enough for me to think that's the problem. In the real world, it happens.
In a perfect world they'd constantly go back and forth from a few percent under 0 to a few percent over zero.
Are they doing anything weird at the same time this issue happens?
That sounds pretty normal though on the STFT's.. the 12% is a bit high but it's not enough for me to think that's the problem. In the real world, it happens.
In a perfect world they'd constantly go back and forth from a few percent under 0 to a few percent over zero.
Are they doing anything weird at the same time this issue happens?
I did have this fun outcome driving back prior to the clutch going AWOL...
https://www.corvetteforum.com/forums...post1590958410