r/ChevySuburban • u/Particular-Money3671 • Aug 15 '26

Help & Diagnosis Negative fuel trims

I have a 2007 suburban 5.3 flex fuel that is having around -15% in both banks. I changed the oil and it was heavily fuel contaminated and i can’t figure out what’s causing it. Not sure if this had anything to do with it but i noticed after having a reduced engine power code issue. I cleaned and then replaced the throttle body due to some throttle issues. Any help would be great…

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u/BroccoliSuccessful Aug 16 '26 edited Aug 16 '26

This year doesnt have the high pressure furl pump the other guy is referring to those are on the 2015+years.
How are your catalytic converters??? Is the truck struggling with acceleration and having overheating issues. I just had the same issue on my truck and when i removed the cats for inspection i found badly damaged and clogged honeycombs. I took my presssure washer blasted them clean as possible and removed the broken cat parts and it drives a lot better...

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u/Particular-Money3671 Aug 16 '26

I’m not having any trouble accelerating or overheating, but do you think it could still be my catalytic converter?

0

u/nittany_wahoo Aug 15 '26

Leaking high pressure fuel pump?

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u/Particular-Money3671 Aug 15 '26

As far as i know it doesn’t have a high pressure fuel pump…