Q: Extremely lean fuel trim

asked by on July 13, 2017

Car has been getting terrible gas mileage and is very sluggish throughout entire acceleration. Plenty of hesitation as well. Maf readings are in spec as well as O2 sensor readings. Initially I thought low fuel pressure but the ltft stays between +20-+25 no matter the rpms the only time it seems to go down is about half way through the acceleration of a gear, say around 2000 rpms and even then jumps between +15-+20. I would expect a low fuel issue, that is not bad enough to cause stalling and more serious issues, to not be as present at idle. I do not have a fuel pressure gauge by the way and do not want to go out to buy one to test the fuel pump before I figure these readings out. I don't understand how THAT lean of a condition can stay relatively the same at idle as it does through out entire acceleration, all the way up to wot throttle there is little variance. In addition bank 1 and bank 2 are identical so clogged injector is out of the mix in my opinion.

My car has 150000 miles.
My car has an automatic transmission.

Hi there. After completing an error code download to verify if this is an electrical glitch first, the next step most professional mechanics would complete is the fuel pressure test. This tends to be the source of an across the board fuel pressure reduction and can be caused by debris in the fuel line, clogged fuel filter or a fuel pump / pressure regulator that is faulty or also clogged with debris. Since your Blazer is nearly 20 years old, it’s quite possible that debris from years of gasoline and carbon deposits are causing this issue. However, without completing the fuel pressure check, you’re likely to keep running into diagnosis issues.

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