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I am losing my mind chasing a fuel trim imbalance issue and figured it would be helpful to see if anyone on this forum has dealt with anything similar.
I am currently getting about a 15-20% difference in positive fuel trims from bank 1 to bank 2. ie bank 1 will be +3% and bank 2 will be +25% etc. I included logs below. Car is a 2009 z06 with a built stroker 442CI w/ a RHS block (made 625whp) - has a Halltech killer bee 108mm air intake - nick williams 103mm TB, and a MSD Atomic Manifold. I am running a Mighty Mouse Catch can as well. Car has long tube headers & a x pipe - factory NPP mufflers. Tuner told me when he put the base tune on the car - he didn't see the fuel trim issue, but when i came back for the final tune the 20-25% delta was there. it does slightly rev hang around 1500 rpm but comes down to idle.
Current tests done to try and figure out the issue.
Swapped 02 sensors out for fresh ones - no change
Swapped coil packs bank to bank - no change
Swapped injectors bank to bank - no change
Swapped spark plugs out for new ones - no change
Smoke tested intake manifold - zero leaks
Compression tested the motor cold - 170-180 psi across the board
Car has long tube headers on it - not really possible for an exhaust leak from the header gaskets to the 02 sensors
I did use a infrared thermometer on the headers after idling it for a while and cylinders 6&8 were ~600 degrees vs others were around 350-425 degrees - would believe this is a lean condition causing the heat difference.
I am kinda at my wits end trying to figure out what the issue could be. If anyone has suggestions I am all ears.
Happy to provide any additional information if more context would be helpful.
If you are seeing a big imbalance between banks it would NOT be something like a MAF sensor or a intake vacuum leak which will affect BOTH banks…this could be something like a bank specific intake runner vacuum leak or bad injectors on that bank…maybe even a clogged cat…can’t read your file so can’t comment…BTW, a misfiring cylinder will cause a lean condition and not a rich one.
Well what were you reading on the O2’s ignition on ??…unfortunately a noid light doesn’t tell you everything …best to use a scope to “current ramp” the injectors and also the coils…injectors draw around 0.9 amps and coils somewhere around 4 amps….a friend of mine did a great video on fuel trims…may be worth watching…are you seeing a P0174 for bank 2 with trim at 25% ??…you may need to do an injector balance test.
[QUOTE=C5 Diag;1609267103]Well what were you reading on the O2’s ignition on ??…unfortunately a noid light doesn’t tell you everything …best to use a scope to “current ramp” the injectors and also the coils…injectors draw around 0.9 amps and coils somewhere around 4 amps….a friend of mine did a great video on fuel trims…may be worth watching…are you seeing a P0174 for bank 2 with trim at 25% ??…you may need to do an injector balance test.
No codes at all from bank 2 trimming at 25%+ - swapped injectors from bank 1 to bank 2 and had the exact same result from a fuel trim perspective - so i feel like that rules out injector imbalance?
02 Sensor Readings were 12v between D & E 8v between B & D and .2v between A & E
All GM narrow band O2's will read a bias voltage of 450Mv's with key ON for all 4 O2 sensors...is that what you see ??...also just a snapshot of short terms is basically useless info...one must look at other live data PIDS to see actually what's going on.
all the 02 sensors key on motor off are right at the 450 ish number + or - 3 mv
as far as PIDS what are you looking for log wise - the intake manifold is off the car right now but I can get additional data logs if i need to get the car back together.
I look at upstream and downstream O2’s, MAP, MAF, ECT, IAT, long and short fuel trims, load,…what are you long terms sitting at ??…if at 25% the MIL will illuminate for a P0171 or P0174.
Ill send you a DM and get your email - i have full logs I can share to give you a better picture of the data.
Can you just record and graph this data and post… looking at these pages of logs isn’t helpful….best to seek a diagnostician to look at this…I also use a labscope and have a special diagnostic scan tool when looking at this stuff…where do you live ??… I may know of a shop.
LS7 Short Term Fuel Trim Issues
