Really fighting Idle Dip
Really fighting Idle Dip Alright guys I have been battling this idle dip since I switched to LS3 heads on my 408 stroker.
Basically everything else is fine, I just can't get the car to 100% idle right. 99% of the time it catches itself but maybe once in a blue moon it will actually die. The problem is that the car seems to just pull fuel then add it back like crazy over and over causing the idle to drop, sit at 400-500 and then slowly recover.
If I blip the throttle before it drops all the way there is a good chance there will not be an issue. Clutch in or out does not matter.
I have a ported LS3 Intake and a factory LS2 Throttle Body with the bigger factory MAF.
Initial tuning was done by NicD but he has been busy (Just got married Congrats man) and honestly the tune is fine except for this and I just don't have the time nor does he for me to make the 100 miles trip one way just to fix it.
I am hoping I can get the help I need to smooth out this issue. I can email the tune file, logs, take screen shots. Not sure what would be preferred for a minor issue like this but I really would appreciate the help. I have tried to do it following a few of the guides posted and I don't seem to have any luck, but if you want to tell me things I should try I am happy to do so as well. I just can't seem to figure getting this thing to idle perfectly by myself.
Basically everything else is fine, I just can't get the car to 100% idle right. 99% of the time it catches itself but maybe once in a blue moon it will actually die. The problem is that the car seems to just pull fuel then add it back like crazy over and over causing the idle to drop, sit at 400-500 and then slowly recover.
If I blip the throttle before it drops all the way there is a good chance there will not be an issue. Clutch in or out does not matter.
I have a ported LS3 Intake and a factory LS2 Throttle Body with the bigger factory MAF.
Initial tuning was done by NicD but he has been busy (Just got married Congrats man) and honestly the tune is fine except for this and I just don't have the time nor does he for me to make the 100 miles trip one way just to fix it.
I am hoping I can get the help I need to smooth out this issue. I can email the tune file, logs, take screen shots. Not sure what would be preferred for a minor issue like this but I really would appreciate the help. I have tried to do it following a few of the guides posted and I don't seem to have any luck, but if you want to tell me things I should try I am happy to do so as well. I just can't seem to figure getting this thing to idle perfectly by myself.
Last edited by Cross; May 12, 2014 at 05:45 PM.
Let me find a way to upload those files, I will load a few logs. Not sure NicD would want me posting the tune I would have to ask him, I don't want him upset with me.
Here is the log, hopefully this works.
http://speedy.sh/x8nv8/4.12.14-Drive-to-Matts.hpl
Or this one:
http://www.filedropper.com/41214drivetomatts
Here is the log, hopefully this works.
http://speedy.sh/x8nv8/4.12.14-Drive-to-Matts.hpl
Or this one:
http://www.filedropper.com/41214drivetomatts
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First off I'd make sure you are not overfueling at idle.
Poor low end VE table fit and poor O2 sensor operation
are likely culprits here. Bad VE fit can come from bogus
AFR readings, tuned-to, and your description sounds like
maybe the MAP-axis fit is part of the problem; the slope
there can fight or reinforce tendency to fuel-surge. If
you have a big cam and try to tune to stoich-indicated,
you will be overfueling the motor in fact because you're
compensating for excess exhaust oxygen read by the meter.
This also bugs NBO2s and you will trim to a rich incoming
mixture due to perceived-lean outgoing. You need to get
the fueling set by minimum-MAP, open loop, and set the
closed loop switchpoints to what-that-reads, averaged
NBO2 voltage, in the relevant airflow-mode cells about
idle.
Idle airflow (running airflow) in my opinion should be set
higher than necessary requiring the RPM loop to pull out
air, not push air in a big hurry to prevent stalling on
idle-entry.
Throttle cracker stuff on some models had weird holes
in the tables which, if you step into them just right,
can give some confusing orders to the IAC or DBW.
You want something smooth and sane there, and as
little as possible.
Poor low end VE table fit and poor O2 sensor operation
are likely culprits here. Bad VE fit can come from bogus
AFR readings, tuned-to, and your description sounds like
maybe the MAP-axis fit is part of the problem; the slope
there can fight or reinforce tendency to fuel-surge. If
you have a big cam and try to tune to stoich-indicated,
you will be overfueling the motor in fact because you're
compensating for excess exhaust oxygen read by the meter.
This also bugs NBO2s and you will trim to a rich incoming
mixture due to perceived-lean outgoing. You need to get
the fueling set by minimum-MAP, open loop, and set the
closed loop switchpoints to what-that-reads, averaged
NBO2 voltage, in the relevant airflow-mode cells about
idle.
Idle airflow (running airflow) in my opinion should be set
higher than necessary requiring the RPM loop to pull out
air, not push air in a big hurry to prevent stalling on
idle-entry.
Throttle cracker stuff on some models had weird holes
in the tables which, if you step into them just right,
can give some confusing orders to the IAC or DBW.
You want something smooth and sane there, and as
little as possible.