Running lean after airaid intake
Tech Contributor
Joined: Jul 2002
Posts: 14,950
Likes: 264
From: St. Louis, MO
St. Jude Donor '08
CEL gets set at + - 25%. If you have a vacuum leak it only comes into play at idle so if idle short term fuel trims were 0 or close it's not a vacuum leak.
Sounds like you need to put your stock tune back in.
Sounds like you need to put your stock tune back in.
Thread Starter
Burning Brakes
Joined: Dec 2014
Posts: 959
Likes: 24
From: Los Angeles, CA
Well would it be possible that since I reflash the car is getting used to the extra air now? And will be OK after this time I cleared it?? When you say 25%?? Is that the number in looking at the fuel trims from the reader???
Tech Contributor
Joined: Jul 2002
Posts: 14,950
Likes: 264
From: St. Louis, MO
St. Jude Donor '08
If I was you I'd flash in your stock tune and see if you get a cel. If not leave it alone or go get a real dyno tune from a reputable tuner.
Thread Starter
Burning Brakes
Joined: Dec 2014
Posts: 959
Likes: 24
From: Los Angeles, CA
The car can correct +- 25% fueling in closed loop, when the o2 feedback calls for more than that it sets a cel. It's normally caused by a mechanical problem like a vacuum leak. The air going into the car doesn't change with a tune and the closed loop fueling may be messed up by a bad maf table in your new tune.
If I was you I'd flash in your stock tune and see if you get a cel. If not leave it alone or go get a real dyno tune from a reputable tuner.
If I was you I'd flash in your stock tune and see if you get a cel. If not leave it alone or go get a real dyno tune from a reputable tuner.
Thread Starter
Burning Brakes
Joined: Dec 2014
Posts: 959
Likes: 24
From: Los Angeles, CA
Sorry for the confusion. I've had CEL under both the stock and aftermarket tune... With both tunes, it takes a long time for the CEL to generate.. Somewhere like 300 plus miles
Tech Contributor
Joined: Jul 2002
Posts: 14,950
Likes: 264
From: St. Louis, MO
St. Jude Donor '08
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Tech Contributor
Joined: Jul 2002
Posts: 14,950
Likes: 264
From: St. Louis, MO
St. Jude Donor '08
I'm going to stick with my recommendation to go back to the stock tune and check LTFT's at idle every 50 miles or so and report back.
If you have a real vacuum leak it'll show up on the LTFT's pretty quickly. I suspect your aftermarket tune is putting a maf table in the computer that it's not liking.
Also check your MAF to ensure it's installed correctly and no air leaks around it. You might buy some maf cleaner and clean it, gently. They are pretty delicate.
If you have a real vacuum leak it'll show up on the LTFT's pretty quickly. I suspect your aftermarket tune is putting a maf table in the computer that it's not liking.
Also check your MAF to ensure it's installed correctly and no air leaks around it. You might buy some maf cleaner and clean it, gently. They are pretty delicate.
Race Director
Joined: May 2004
Posts: 16,667
Likes: 1,209
From: Raleigh, NC
St. Jude Donor '15
I would check them while actually driving.
10% LTFT's isn't that unusual nor is it a problem. STFT's will typically be closer to 0 (as long term changes are saved into LTFT's.. thus their name)
Like Joe already mentioned.. LTFT's can go to 25% and STFT's on top can make the total even higher than that. I've seen 30 something % before, but it was only because I had another problem with the evap system. I'm assuming it would have eventually set a CEL but I fixed it soon after noticing it.
10% LTFT's isn't that unusual nor is it a problem. STFT's will typically be closer to 0 (as long term changes are saved into LTFT's.. thus their name)
Like Joe already mentioned.. LTFT's can go to 25% and STFT's on top can make the total even higher than that. I've seen 30 something % before, but it was only because I had another problem with the evap system. I'm assuming it would have eventually set a CEL but I fixed it soon after noticing it.
Thread Starter
Burning Brakes
Joined: Dec 2014
Posts: 959
Likes: 24
From: Los Angeles, CA
Well I just checked them while driving... At constant speed using cruise control at 70mph, LTFT were steay around 10 or so.. STFT were up and down.. Cancel cruise control and during Decel, Steay at 0 for ST and 12 for LT. City driving up to 40mph, ST is up and down from -7 to 5 bit mainly steady around 0 with -1 to 2 being more present. LT steady around 10 with small changes to higher..
Got home and parked, so idle, LT set at 10. ST up and down near 0.
I will keep checking the FT.. I just don't understand... If it was a leak that's making the car run lean, wouldn't it happen right away...
Like I said it usually drive like 10 mines to work everyday and then back home.. During those drivr before no CEL.. The CEL had appear only during long highway drive..
Got home and parked, so idle, LT set at 10. ST up and down near 0.
I will keep checking the FT.. I just don't understand... If it was a leak that's making the car run lean, wouldn't it happen right away...
Like I said it usually drive like 10 mines to work everyday and then back home.. During those drivr before no CEL.. The CEL had appear only during long highway drive..
Tech Contributor
Joined: Jul 2002
Posts: 14,950
Likes: 264
From: St. Louis, MO
St. Jude Donor '08
I don't think you have a leak, I think your aftermarket tune is putting in a maf table that is causing it to run lean. When you get a chance check ltfts at highway cruising speeds.
Thread Starter
Burning Brakes
Joined: Dec 2014
Posts: 959
Likes: 24
From: Los Angeles, CA
Will do. Idk when its the next long trip ahead so it might be a while.. Well see.. Started logging miles with no issues... It just seems like the issue only happens when the car is driven for a while..
Thread Starter
Burning Brakes
Joined: Dec 2014
Posts: 959
Likes: 24
From: Los Angeles, CA
Alright guys.. I've been over 300 miles since I clear the CEL. No CEL has returned. Today I actually went for a cruise of about 150 miles where I had all driving type (highway, mountain, bumper to bumper traffic, normal city). I waited until the end to to start checking my FT, but in freeway driving, they were normal LTFT was aroubd 15 or so and ST was up and down around 0. However, in bumper to bumper traffic, my LTFT went up all the way to 24. This was only why the car was idling in traffic. ST was 0 or as close to it. Coolant temp was 214 and Intake temp was 140. Anyways.. As soon as I would drive event a little bit, the LT would reduce to around 15 and as soon as the traffic opened u, fuel trims were normal at LT aroubd 15 or so and ST around 0 and engine temp dropped about 50%.
At the end no CEL still.. Should I worry? Or am I good?
At the end no CEL still.. Should I worry? Or am I good?
Thread Starter
Burning Brakes
Joined: Dec 2014
Posts: 959
Likes: 24
From: Los Angeles, CA
Race Director
Joined: May 2004
Posts: 16,667
Likes: 1,209
From: Raleigh, NC
St. Jude Donor '15
Yeah LTFT's that high is borderline on setting a code.
Some basic adjustments to the MAF and VE tables with HP Tuners would bring those down closer to zero.
Not too unusual for them to drift up while sitting in traffic. There's a way to fix that too that a decent tuner can take care of for you.
Some basic adjustments to the MAF and VE tables with HP Tuners would bring those down closer to zero.
Not too unusual for them to drift up while sitting in traffic. There's a way to fix that too that a decent tuner can take care of for you.
Tech Contributor
Joined: Jul 2002
Posts: 14,950
Likes: 264
From: St. Louis, MO
St. Jude Donor '08
You need to ditch that canned tune. It is clearly not right for your car.
I will stop saying it now. I've said it a dozen times in this thread.
Thread Starter
Burning Brakes
Joined: Dec 2014
Posts: 959
Likes: 24
From: Los Angeles, CA
Ok. I am going back to stock. What's a decent city mileage? I am getting a custom tune done when I installed headers then I'll also include the intake to be tuned.