Hi all. When I check the data stream on my code reader from time to time (at idle/warmed up), my fuel trims are always high. However, they are sometimes barely above zero and other times they are as high as +13. They never go into the negative. My MAF sensor usually reports low (below 2.4 gps) and the lower it reports, the higher the positive FT. The lambda ratio is always close to 1 but ever so slightly on the "rich" side. I don't understand why the trims vary so randomly or why they are too high anyway. There are no trouble codes and the engine idles pretty smoothly, although it's sometimes a little rough (vibration) usually only in park. Any ideas for what I should check? I should add the engine was recently rebuilt, but my fuel trims were always somewhat above normal. Any advice is appreciated as always!
High Positive Fuel Trim -sometimes-
- Thread starter Jonas
- Start date
Is it on the 2009 Vibe....1ZZFE engine?
Yes the Vibe, 2AZ FE (2.4L) engine
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weak fuel pump/dirty sock?
What is a dirty sock in this instance?
in tank fuel filter, located on the pump or pickup tube
Right. Again, I hope not lol. The fact that the fluctuation in fuel trim is so random is what's confusing. The car seems to run fine, but the OBD shows it's adjusting for something.
A vacuum leak can cause higher fuel trims and I guess could reduce the amount of air going through the MAF. I've not heard of too many intermittent vacuum leaks, though.
I know, it's weird. I'm not sure, but it seems to get worse after driving for a couple of hours. The car feels less peppy after a while, but it could just be fatigue on my part. I'm a delivery driver, BTW.
It is possible the catalytic converters gasket get a leak after heating up and air gets in. Resault is an extra fuel trim.
Edit: I have almost same thing with my CRV, but it is to cold to get under for investigation.
Edit: I have almost same thing with my CRV, but it is to cold to get under for investigation.
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They are both high (short and long term) but the STFT tends to be higher and they vary throughout the day.
I hope not, but I did have to fix a stripped screw in the exhaust that was causing a rattle. Maybe the new cat wasn't installed/torqued properly.
I've cleaned it a few times before with MAF cleaner. It looks clean to me.
Have you used injector cleaner, like Techron?
I'd just drive on and wait for a "real" symptom.
gathermewool
Site Donor 2023
What values are you seeing for LTFT? Ignore STFT unless you can log the exact values and compare them.
With the engine idling, look at the Short Term Fuel Trim (STFT) and Long Term Fuel Trim (LTFT) values. Normal range may be high as plus or minus 8, but closer to zero is best. If the numbers are +10 or higher for STFT and LTFT, your engine is running LEAN.
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