Help Troubleshooting Fuel Trims

[GregBunney]

I ran into a similar issue years back. Not the same but had high fuel trim issues. My long term trims were high after a 2+ hour road trip. After the MAF and MAP sensor replacement without changes, I found it to be a fuel pump issue. The previous owner had had the pump replaced but they didn't crimp the new electrical wires together. They twisted the ends together and taped them up. After the replacement and proper crimping of the wires, better trims and no issues since.
Again maybe not the same but just thinking it could be a pump issue.

Tested today, primed at 53-54 and ran at about 42-43. Fuel pump time probably?

 

[GregBunney]

Many auto parts stores will "rent" them for a credit card deposit that is refunded when the kit is returned.

Tested today and came back 53-54 at prime and 42ish running. Fuel pump time?

 

[mhaywoodcz]

I would say it can't hurt. I also had the MAF or MAP codes,(can't remember).
Fuel pump would at least eliminate that issue

 

[Fless]

I think you said this is a gas system, not Flex Fuel, so it shouldn't have an inline fuel filter (I think).

For fuel pressure, according to Haynes:
KOEO
Flex Fuel: 48-54 psi
Non-Flex: 55-62 psi

 

[West 1]

To see 25% on both banks you either have a large vacuum leak or something similar throwing off your data. What are your Bank 1 sensor 1 and bank 2 sensor 1 O2 sensors showing?

The fuel trim adjustments are driven by O2 sensor information from the before Cat O2 sensors.

The after cat sensors mostly tell you if the Cat is working properly the before Cat sensors feed tune information to your computer to adjust fuel trims.

I have repaired engines that had very high LTFT readings and the trims corrected right after the repair was completed. I have not seen the 25% #’s on both banks ever so I am curious what you end up finding as the cause.

Is your gas mileage terrible? Is the power weak? I would fix this quick before your cats are ruined.

 

[Marky Dissod]

If MpGs are down due to running rich, not only are the catalytic converters aging more quickly,
but you gotta change the motor oil more often too, 'cause more of that excess gas sneaks past the piston rings.