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2004 gto running rough after hot start then clearing up
I have a 2004 gto that has a 228/230 cam, 243 heads, dorman ls2 intake, a warr 92mm tb, and headers I got the car tuned in early February and everything was great until recently. When you start the car in the morning it runs great no problems at all however after you drive it for any distance at all and turn it off long enough to pump gas (or longer) it runs terrible until you get on it pretty good. I have a wideband o2 sensor in the car and it is going completely lean when it starts to stumble after a warm start. After you get on it and it clears up you can drive it as far as you want with no problem but as soon as you shut it off and start it back up it runs bad until you get on it again. The car is not throwing any codes and I am at a complete loss with it. I have access to hp tuners and could data log it if that would help
I am wondering if it is starting in open loop, and while there the calibration is off, then once back in closed loop all is well again. When running bad, does it seem to be running very rich or lean? A data log would be very helpful here. It will tell us what's going on...
Would like to hear the solution to this also..seem to have a similar problem with mine..02 formula with a cam only LS1..starts and runs perfect when cold, but shut it off after its been warmed up and try and restart it and it won't idle unless i mess with the throttle.
Well hopefully we can get it figured out. If these guys on here can’t get us pointed in the right direction there’s probably not anyone that can ��
lol..ive read that the IAC can cause funky idle issues so i looked around and bought an OEM replacement AC delco IAC from Walmart of all places for 80 bucks, picking it up tomorrow, so im gonna see if that helps at all, if not its going back to the place that tuned mine and have them figure it out.
I am wondering if it is starting in open loop, and while there the calibration is off, then once back in closed loop all is well again. When running bad, does it seem to be running very rich or lean? A data log would be very helpful here. It will tell us what's going on...
I have attached two HPT log files from 2OO4 GTO's car. For some reason it is pulling timing I think that is the issue. What do you think? One file is it cutting out doing normal driving and the other file is when he is getting on the stall and it is cutting out. Once he really gets on it everything runs fine.
I have attached two HPT log files from 2OO4 GTO's car. For some reason it is pulling timing I think that is the issue. What do you think? One file is it cutting out doing normal driving and the other file is when he is getting on the stall and it is cutting out. Once he really gets on it everything runs fine.
Thanks,
Interesting! Now it sounds like it's messing up IN Closed Loop! Might be the CL tune that's messed up! Because when you are REALLY on it(WOT), it goes into open loop.
Id be shocked if it is somethimg in the tune. Has been fine since Feb and starts out of nowhere. Either that or you just havent did a hot restart since it has been tuned? The tune shouldnt change is what im saying, especially a closed loop tune. Maybe its an open loop tune and the iat is getting heatsoak? But if someone put it open loop for those mods would be crazy.
On the second log, upon startup it is very very rich. This will cause misfires. In some instances i see over 30% over fueling, well into the 10s. IF thats not the case, then your o2s are pulling 30% fuel, when in fact the fueling is accurate, making the airflow tables lean by 30%. This could be caused by a o2 transport delay, or lack of. Enabling the o2s too early could cause them to pull or add fuel inaccurately giving you issues.
Since there is no HPT file, and no log with the wideband being logged, that's all that can be determined at the moment.
On the second log, upon startup it is very very rich. This will cause misfires. In some instances i see over 30% over fueling, well into the 10s. IF thats not the case, then your o2s are pulling 30% fuel, when in fact the fueling is accurate, making the airflow tables lean by 30%. This could be caused by a o2 transport delay, or lack of. Enabling the o2s too early could cause them to pull or add fuel inaccurately giving you issues.
Since there is no HPT file, and no log with the wideband being logged, that's all that can be determined at the moment.
I will get a file of the tune put up sometime today it might be after 5 before I can have it done. Thanks for your response
[QUOTE=Lsxford;19949820]Id be shocked if it is somethimg in the tune. Has been fine since Feb and starts out of nowhere. Either that or you just havent did a hot restart since it has been tuned? The tune shouldnt change is what im saying, especially a closed loop tune. Maybe its an open loop tune and the iat is getting heatsoak? But if someone put it open loop for those mods would be crazy.
I have drove it with plenty of hot starts since I had it tuned in February with no problem until maybe the last month.
check your IAC when the car is cold..see what the position of the valve is..if its all the way extended and looks gummed up with crap like this, either clean it or change it..had very similar symptoms as yours and a new IAC fixed the warm start issue. FYI walmart has the cheapest AC delco IAC around, got it for 80 bucks..all other parts stores wanted around $150.
I would suggest the cut out off the converter from stall is a combination of torque management, burst knock retard and the delay to enable power enrichment. no PE is leaving it lean causing burst knock and likely actual knock.
I would turn STFT in open loop off
using cranking FA fuel
base idle airflow
start up airflow (multiple)
start up flare control
08-14-2018, 10:28 AM
2004 gto running rough after hot start then clearing up 
