Fuel trims go way "lean"...advice?
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Fuel trims go way "lean"...advice? Hello,
I don't have an LS1 tuner just yet, but I used my DHP powertuner (for my Olds) to scan my camaro. I'm able to log some parameters, but not all. I wanted to check because I did hear some pinging while racing the car down the track.
Well my fuel trim goes way into the positive as I get over 30% throttle. Ideally I'd want it as close to 0, but it's reading between +10 to +19 as I give it more throttle. Car has some mileage obviously, but it seems it's starving for fuel. What would be my best plan of attack? I was thinking in this order:
- New fuel filter (done)
- Change plugs (unknown when it was done, already found one loose)
- Seafoam the engine
- Remove injectors, send out to have cleaned/serviced at witchhunter
- replace upstream oxygen sensors (necessary, or overkill?)
Could the PCM be doing something because my cats are bad? I get code P0420 and P0430 even after changing the downstream O2. I need to get the service done at the dealer, since it's an '00 and GM sent out a notice about the cats going bad early.
Any other ideas prior to buying a tuner and making adjustments? Could simple mods like the airlid throw the tune off like that?
Thanks!
I don't have an LS1 tuner just yet, but I used my DHP powertuner (for my Olds) to scan my camaro. I'm able to log some parameters, but not all. I wanted to check because I did hear some pinging while racing the car down the track.
Well my fuel trim goes way into the positive as I get over 30% throttle. Ideally I'd want it as close to 0, but it's reading between +10 to +19 as I give it more throttle. Car has some mileage obviously, but it seems it's starving for fuel. What would be my best plan of attack? I was thinking in this order:
- New fuel filter (done)
- Change plugs (unknown when it was done, already found one loose)
- Seafoam the engine
- Remove injectors, send out to have cleaned/serviced at witchhunter
- replace upstream oxygen sensors (necessary, or overkill?)
Could the PCM be doing something because my cats are bad? I get code P0420 and P0430 even after changing the downstream O2. I need to get the service done at the dealer, since it's an '00 and GM sent out a notice about the cats going bad early.
Any other ideas prior to buying a tuner and making adjustments? Could simple mods like the airlid throw the tune off like that?
Thanks!
Definitely not bad ideas given the mileage. So, I wouldn't say overkill. I'd also include "new paper air filter" and "clean the MAF" to that list since that will only run you another $15.
Have you ruled out the possibility for leaks (vacuum or exhaust)???
Have you ruled out the possibility for leaks (vacuum or exhaust)???
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Yeah I did clean the MAF when I first bought the car, and at the moment I'm going to change back to a paper filter (later on I'll go with an amsoil filter). I don't have any exhaust leaks, and no noticeable intake leaks. I'll post a scan later tonight. My fuel trims hit +25 during highway acceleration. Not to much knock though, maybe 3 degrees max.
I'd point to the MAF or O2 sensors still. Did you (or the previous owner) de-screen your MAF? The only other thing I might think is unstable fuel pressure. You could hook up a guage to measure fuel pressure at the rail. It should be 58psi at all times.
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Do keep in mind when your at 30% throttle accelerating the o2 sensor is ignored (fuel enrichment mode). The computer mostly looks at the tps, the maf and coolant temperature when accelerating. Long term fuel trim is always going to be positive when in fuel enrichment mode. If your pinging try to run higher octane gas, if this corrects the issue you may have carbon build up.
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Originally Posted by SSpdDmon
I'd point to the MAF or O2 sensors still. Did you (or the previous owner) de-screen your MAF? The only other thing I might think is unstable fuel pressure. You could hook up a guage to measure fuel pressure at the rail. It should be 58psi at all times.
Do keep in mind when your at 30% throttle accelerating the o2 sensor is ignored (fuel enrichment mode). The computer mostly looks at the tps, the maf and coolant temperature when accelerating. Long term fuel trim is always going to be positive when in fuel enrichment mode. If your pinging try to run higher octane gas, if this corrects the issue you may have carbon build up.
when in fuel enrichment, isn't the fuel trims supposed to be locked in at (or close to) zero ideally? That's how it is on my V6's PCM. I noticed as I drove (45 minute commute to work) fuel trims progressively became more positive. I always run 93 octane fuel, and the time at the track I heard pinging, it was also 90 degrees out. I borrowed the Run-Rite kit for cleaning the combustion chamber, I'll give that a shot. Trending Topics
That's a little mis-information. IIRC it can take 60% throttle before PE will kick in at lower RPMs. Above 4,000rpms, I believe it'll only take 25%. It's a simple TPS% vs. RPM look-up table in the PCM. It's not flat though...takes more down low to switch to open loop.
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Yeah my Cutlass V6 PE enable was 70% stock, and would go down to about 45% at the higher RPM's. But still, from my experience, fuel trim #'s would not go positive because it's commanding PE, unless something's different with this PCM.
Fuel trims and PE are seperate.. when the car goes PE it won't show that in the trims or have any bearing on the trims but... + trims at WOT means its adding the LTFT trim % and the PE value. My car was 14 % off with my minor engine mods and it would show on the wideband because the car would comand 12.7 but actual was always around 12-16% richer than comanded. After I cleaned up the LTFT's using a good VE tune and MAF tune the car was within a few Percent of comanded at WOT.
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This makes me want to get a tuner for the Camaro, stat! I have a lot of fun using the powertuner on my Olds. In fact I just recently re-did some tuning on it, and it drives even better now.
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I did plugs, seafoamed the combustion chambers (lots of smoke), cleaned the MAF again. Still showing lean however. I did one scan this morning showing this, and on the way home I'll scan it again with the MAF unplugged. I'll keep updating.
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unplugging the MAF helps a little, but it runs like crap (acceleration isn't smooth) Here's a quick chart I did of TPS vs Fuel trim (LTFT + STFT) using just the LTFT values gives similar results, but I scanned after a recent trouble code/fuel trim clear. If I can log engine RPM, that might be more accurate. But anyway, you can see how far positive it goes.
