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Anyone have fuel trim data they can post from their car? STFT and LTFT for both banks.
My 2015 C7 Z51, shows the left bank operating at -5% to -8% after a long drive.
Where as the right bank is usually at 0%, sometimes +/- 2%.
Note: i recently replaced 4 injectors on the left bank, right bank is original to the car. I dont have data before i did the work.
Car runs fine with above specs. Moreso wondering if this is a common thing, or my new injectors are simply adding 5-8% more vs stock. Or a sensor is slightly out, etc.
You really don’t need to look at anyone else’s trim data…fuel trims should not be more than plus or minus 10%…are these injectors OEM ??…where did you buy them and why were they changed in the first place ??…your new injectors are probably adding fuel…a bad sensor would involve both banks.
I'd expect them to line up pretty well....within a few points of each other. The absolute values you're seeing are heavily influenced by other things but if this is an other wise stock car....it's unusual to see the split. The engine has o2 sensors for each bank so the values will vary bank-to-bank but should be close.
Regarding injectors, GM sells three part numbers for the injectors. One is "High", one is "Nominal", and the other as you'd expect is "Low". These designate the flow rate vs the spec. "High" injectors for instance will flow slightly more fuel. Enough to affect the fuel trims don't know but for GM to go through the hassle of different part numbers and inventory I'd say they might. Did you look at the part number on your old injectors or just buy new injectors for your year car? You may have mismatched injectors.
The other possibility is that depending on miles, DI injectors can get a little dirty around the tips. A buddy of mine had his flow tested/rebuilt on a 20k mile car. His injectors had a flow rate range of +/- 20%....that's a LOT.
The below log is mine and is while I'm on track. The point of it is you can see the STFTs bouncing all over as the engine goes through various rpm and load transitions. The LTFTs are on top of each other. When it's in PE mode they do this by design but as you can see looking at the 1 minute of data that I took a screenshot of, even when the car is not in PE mode the trims match nicely. I circled where the fuel trim row is...
TLDR....I wouldn't be surprised if the old injectors need to be cleaned or you have mismatched flow rates between banks.
New OEM GM injectors from rockauto. Existing part is nominal flow, new ones nominal flow. Look identical. Tips of old injectors were clean. Why change? Because cyl 5 had a misfire.
96GS, thanks for info. Il probably end up replacing the other 4 next month.
How did you know the flow was good ??…you did an injector balance test ??…I advise members trying to diagnose a misfire that anything beyond plugs and wires they don’t have the advanced diagnostic equipment to diagnose these…this was a list off the top of my head as to the various causes…and unfortunately a dealership or general repair shop will only replace parts.
You should have just posted to the thread you already started above instead of starting a new one so we can see what you’ve done…find a diagnostic shop…they will diagnose it to ONE part .
I wouldn't worry too much over this. You are within norms of 10% as you know. OTOH my gut feeling is this is old vs new injectors. Clean visually may not mean flow is slightly reduced due to age. You could swap all L to R and all R to L but that is probably too much work as a test. To me it would be a Q of how much another 4 injectors would cost vs getting LTFT closer to zero.
Fuel trims are not bad. After replacing one bank of injectors then comparing bank to bank fuel trims one can expect to find a variation. Again the fuel trims are in an acceptable range.
C7 fuel trim data
don't know but for GM to go through the hassle of different part numbers and inventory I'd say they might. Did you look at the part number on your old injectors or just buy new injectors for your year car? You may have mismatched injectors.
