Running rich?

[stutaeng]

Lean? I thought you said in the beginning it was running rich, but others said it's actually running lean...I can't really see the photos on my phone too well...

What do the fuel trims do when you rev it up? Sounds like it's a fuel delivery problem by your information about fuel pressure, which is consistent with system running lean. When you rev the engine also monitor fuel pressure. Better yet, check these things while actually driving to simulate real conditions.

Maybe engine runs rough under load because the pump can't deliver enough fuel for the demand? The fuel trims will show you this.

 

[stutaeng]

Also, both banks running lean at the almost exact percentage is going to be dead giveaway that it's fuel delivery problem.

A vacuum leak (for lean condition) or clogged or leaky injector (for lean or rich condition) will usually show up as one bank being affected. Fuel delivery affects both banks.

 

[Frank Enstein]

Bad grounds on the O2 sensors will show lean even when it's pig rich.

Also misfire will show lean as well.

 

[99BB3500]

In my opinion it was running rich. I’m not real good at diagnosing problems. But with the STFT being -10 I thought the computer was leaning it out. You may be right. I’m not 100% sure. That’s why I posted here. If there is any confusion I apologize

 

[stutaeng]

Yes, negative fuel trim values is ECM cutting back fuel, so that's a rich condition. Positive values is ECU adding extra fuel... lean condition.

Did you ever get any rich or lean SES codes?

 

[Schurkey]

Yes, negative fuel trim values is ECM cutting back fuel, so that's a rich condition. Positive values is ECU adding extra fuel... lean condition.

Sort of.

If the O2 sensor(s) are providing false data, the computer may lean-out ("Lean command") or enrichen (Rich command) the mixture, without there being a true rich or lean condition. The computer is trying to fix a problem that may not exist.

Paying attention to fuel trims is a TOTAL waste of time until the O2 sensor system is verified.

Thus the importance of an O2 sensor system (sensors, wire harness, no exhaust leaks, no misfire, etc.) that's actually working properly.

Did you ever get any rich or lean SES codes?

Good question.

 

[stutaeng]

Sort of.

If the O2 sensor(s) are providing false data, the computer may lean-out ("Lean command") or enrichen (Rich command) the mixture, without there being a true rich or lean condition. The computer is trying to fix a problem that may not exist.

Paying attention to fuel trims is a TOTAL waste of time until the O2 sensor system is verified.

Thus the importance of an O2 sensor system (sensors, wire harness, no exhaust leaks, no misfire, etc.) that's actually working properly.


Good question.

Agreed. There more information to look at...

 

[99BB3500]

No rich or lean condition at all. What all do I need to look at? Only other things I haven’t replaced with the fuel system are the line itself, the injectors and the FPR

 

[Schurkey]

No rich or lean condition at all. What all do I need to look at?

You need to shiitcan every O2 sensor on the vehicle. You know for a fact that one is throwing a code, two others are acting goofy with almost no voltage variation, and you're suspecting all of them are old.

AFTER you've replaced the sensors, run the engine to closed-loop operation. Use the scan tool to verify that the ones in front of the converter rapidly shift from rich to lean (reasonable voltage crosscounts, which is probably an actual line item in the scan tool) and the ones behind the converter has more gradual voltage changes. ('Course, you need to have converters installed...)

 

[99BB3500]

I’m assuming they are old yes. Hell they could be original for all I know. I don’t really mind changing out stuff on it just for piece of mind alone. I intend on keeping the truck as long as possible