2006 C6 System Too Lean Codes? Random Misfiring?
Thread Starter
Cruising
Joined: Oct 2022
Posts: 12
Likes: 0
2006 C6 System Too Lean Codes? Random Misfiring?
Hello Everyone, I have a 2006 A6 LS2 Corvette (Long Tube Headers, Vararam Intake, Dyno Tune) that randomly leans out / starts jolting sometimes when coming to a stop. In the past 6 months I've had lifter work done including head gaskets and had to fix my torque tube as well. The car will drive fine for an hour sometimes and then when coming to a stop the car will start idling insanely rough. I have been able to get past this by turning the car off which seems to reset whatever problem the car thinks its having. I do have a small vacuum leak from my boot before the MAF I discovered during a smoke test but its very minimal. The code I seem to get when the issue occurs is P0174 (Fuel Trim System Lean Bank 2). Does this potentially sound like a failing sensor, a weak fuel pump, a tuning or ECU issue? Trying to make sure its running 100% before I get it sold, any advice appreciated!
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,565
Likes: 4,034
From: Cape Coral, Florida
You first need to know what your fuel trims are on both banks…if bank 1 is ok then it is something only on bank 2…high bank specific fuel trims would not be a weak fuel pump or MAF sensor…a weak pump or under reporting MAF will affect both banks…if just bank 2 is elevated run the car at 3000 RPM and if the fuel trims decrease on that bank you have a vacuum leak…if no vacuum leak an O2 sensor “stuck” rich which is over 450 mv’s will pull fuel (decreased injector pulse) and cause a lean condition.
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,565
Likes: 4,034
From: Cape Coral, Florida
With those Long Tubes the upstream O2 sensors don't like that because they are much further back into the exhaust stream vs the OEM...has this car been tuned for those ??...that's why I don't run that crap on my car.
Drifting
Joined: Aug 2022
Posts: 1,478
Likes: 421
From: Ruskin, FL
Thread Starter
Cruising
Joined: Oct 2022
Posts: 12
Likes: 0
These are the fuel trim data videos that I took one at idle and one at 3000rpm. I believe I have freeze frames of the fuel trim from one of the times the issue occurred I will have to try and find them. The car was dyno tuned a few years ago. Im starting to lean towards a tuning issue but I will check the o2 sensors tomorrow. A few years ago I had a similar issue where the wiring harness extension for the 02s melted and was causing the car to stall out but it was happening on every drive cycle. The random timing of the issue is what I think is throwing me off, its almost like the issue happens after the car heats up for a while. Let me know what you think and if I can get anymore information to help!
I upload these two videos to Youtube but if they're are not clear enough lmk.
I upload these two videos to Youtube but if they're are not clear enough lmk.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
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
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,565
Likes: 4,034
From: Cape Coral, Florida
If fuel trims increase under load it’s either a MAF or fuel delivery issue…fuel pump or clogged injectors…look at your upstream O2’s up to WOT…they should go full RICH…like 900mv’s or a little higher.