Got my car tuned...questions...
Got my car tuned...questions... I just completed my STS build and got my car tuned. The tuner said the car keeps leaning out at idle and didn't know why. It stalls sometimes when coming straight off the throttle to the brakes(as it leans way out). It DOESN'T lean out when in higher rpms, just at idle. What could be causing this? The tuner suggested replacing the O2 sensors. BTW, the fuel pressure was fine all the way around. There are no problems visible to the eye. Could it be electrical or computer problems? I'll post the Dyno sheet soon but here are the Stats: 4lbs. boost= RWHP=391, Torque=404. 
Ummm. What o2 sensors I see a 3 bar map are you speed density? If so the fronts may need to be replace but the rears should have no affect since speed density is rpm, iat, and air flow given at a rpm. How much psi are u planning to run a 3 bar is kinda high imho I use a 2bar on mine from a colbalt ss gm plug and play. What is your fuel pressure at Idle and hows the system set up. If its running super lean at I dle it may be in the tune have you posted in the pcm and tuning?
It's an SD tune with only the front O2 sensors. It is a 3 bar MAP sensor and I plan on running around 8 psi. The tuner said he checked the fuel pressure and it was fine, I don't have the numbers on that. It's a racetronix fuel pump upgrade. He even tried throwing extra fuel in on the bottom. Didn't work. I plan to go ahead and replace the O2 sensors. I hate to throw money at it just to HOPE that it solves the problem, but I want even more to drive this thing when it's right.
The front 02 sensors should be replaced every 30,000 miles for optimum performance, and most are not replaced until they throw a code. I'd replace the front 02 sensors and see if it helps, but the car should not of left the tuner until the problem was resolved. Bob
The front 02 sensors should be replaced every 30,000 miles for optimum performance, and most are not replaced until they throw a code. I'd replace the front 02 sensors and see if it helps, but the car should not of left the tuner until the problem was resolved. Bob
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Joined: Jun 2008
Posts: 46
Likes: 0
From: Mississippi
Mine was doing the same thing, the tuner told me that because of the piping, the engine was not getting the air it should at idle. So in about 10min on his comp. he had it fixed. But if ur running lean that might not be ur prob.
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Map?? Ide call Jerremy Farmato!! His # is 813-495-8778 and he's one of the best around at tunning our rides. Ide bet it the 3 bar messen with you! You should have went with the 2 bar off the Colbalt SS like the other guy said. Thats the map sensor Jerremy recommend for my APS build too on which he tunned it with no problems whats so ever, and boost is good to 14.5 with the 2 bar. Also, from what ive researched,,,,the 2 mar is more user freindly and preceise threw out the whole RPM range including ideal and you give up some of that with the 3 bar sensor. Now,this is just what ive read on here and from what other tunners have told me ????It could just be the tune too???Either way, i'de call Jerremy and ask him what he thinks ,he's a really cool guy
Good luck to ya and keep us posted
Good luck to ya and keep us posted
I had opposite problem until recently think its pretty much fixed. I was really rich at idle. I have 60 pound injectors and running 3 bar speed density tune. I now doubt that will ever go over 15psi so 2 bar would have done it for me but whatever for now sticking with the 3 bar tune.
So assume you have bigger injectors not sure if you mentioned how big. Could be problem the IFR on the injectors being setup up wrong or could have to tweak ve at idle..If the 02s are cycling good at idle doubt its them. Mine were cycling good off idle but not at idle and just got some new ones but now it seems the problem was tuning.
Also gm is super expensive for the 02s. You can likely get them a lot cheaper from walker,ngk or bosche.I just picked up some bosche for less than half of what the stealership wanted up here in Canada. They are not the universal type but the plug and play oem type. Even if dont' need them right now nice to have a spare set.
So assume you have bigger injectors not sure if you mentioned how big. Could be problem the IFR on the injectors being setup up wrong or could have to tweak ve at idle..If the 02s are cycling good at idle doubt its them. Mine were cycling good off idle but not at idle and just got some new ones but now it seems the problem was tuning.
Also gm is super expensive for the 02s. You can likely get them a lot cheaper from walker,ngk or bosche.I just picked up some bosche for less than half of what the stealership wanted up here in Canada. They are not the universal type but the plug and play oem type. Even if dont' need them right now nice to have a spare set.
Tuner should have disabled the stock O2's and seen if that was the problem. Also as mentioned, there are only so many cells to work with on the VE map. By going to 3 bar, you cut your resolution down significantly. Regardless, sounds like your setup is pretty mild and a decent tuner should have been able to nail it pretty easy unless you have some other mechanical problem. It has been my experience that bad narrow bad O2's usually drive the idle extremely rich unless the open loop fueling table has been tampered with.
Joined: Jun 2004
Posts: 1,501
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From: Ft. Irwin, California (But Virginia is home)
You could have a couple issues causing the problem. Changing the front O2's to ensure they are NOT the problem is never a bad idea.
Concerning tuning, it sounds like either the base running airflow was not properly set for the cam, or the fuel adder vs IAT/ECT is not properly adjusted. Either way, I agree that this should have been fixed while the car was being tuned. Just my $0.02
Oh, and 12.8 is way too lean at WOT for the A/F ratio. However, if they were using a probe in the tailpipe, then you might be fine. When I dyno-tuned my STS last year, the AEM in the car showed 11.1 to 0 fuel ratio. The dyno wand in the tailpipe showed 12.5. Why the difference? Guessing turbulence from the dump pipe I was running out the turbo was affecting the dyno probe readings.
Anyhow, hope this helps ya' a bit.
Concerning tuning, it sounds like either the base running airflow was not properly set for the cam, or the fuel adder vs IAT/ECT is not properly adjusted. Either way, I agree that this should have been fixed while the car was being tuned. Just my $0.02
Oh, and 12.8 is way too lean at WOT for the A/F ratio. However, if they were using a probe in the tailpipe, then you might be fine. When I dyno-tuned my STS last year, the AEM in the car showed 11.1 to 0 fuel ratio. The dyno wand in the tailpipe showed 12.5. Why the difference? Guessing turbulence from the dump pipe I was running out the turbo was affecting the dyno probe readings.
Anyhow, hope this helps ya' a bit.
If the car has hptuners tune if you can post it we can help more. Is this car m6 or auto. For now you can maybe raise idle and that might work not always the best method but sometimes not the worst either. You have a very mellow cam it should idle like a baby.
As said if you have injectors IFR set wrong that might be the problem it would be lean thruout the range if the IFR is set wrong.
You can also raise spark a few degrees at idle or possibly raise ve around the idle rpms.
I doubt you would have to play with idle airflow that much with that mild a cam but as said maybe all that piping changes things.
LIkley not the problem but you are sure you have good plugs,wires.fuel filter.
Any codes being thrown?
As said if you have injectors IFR set wrong that might be the problem it would be lean thruout the range if the IFR is set wrong.
You can also raise spark a few degrees at idle or possibly raise ve around the idle rpms.
I doubt you would have to play with idle airflow that much with that mild a cam but as said maybe all that piping changes things.
LIkley not the problem but you are sure you have good plugs,wires.fuel filter.
Any codes being thrown?
Oh, and 12.8 is way too lean at WOT for the A/F ratio. However, if they were using a probe in the tailpipe, then you might be fine. When I dyno-tuned my STS last year, the AEM in the car showed 11.1 to 0 fuel ratio. The dyno wand in the tailpipe showed 12.5. Why the difference? Guessing turbulence from the dump pipe I was running out the turbo was affecting the dyno probe readings.
Anyhow, hope this helps ya' a bit.
Your differance might just be 2 diff o2 sensors and one of them not reading correctly. We use a tailpipe probe( the brand new Dyno Jet one) and it is DEAD on if we switch the O2 into a bung.