Running very lean

[Muse]

My car is running very lean, and my mechanic is stumped. I can drive it fairly well as long as i barely touch the gas. it'll do highway speeds, with no issues, as long as I'm willing to take a while to get to them.

We've ruled out fuel pressure issues, as it's got plenty of pressure. I swapped the MAF sensor from my other car on, that didn't fix it. He clamped off the return line to the fuel filter, and that did nothing, which (according to him,) should have killed the engine. it does not appear to have a vacuum leak of any kind. And lastly, when he disconnected the fuel line to put the pressure tester on, it spurted fuel back from the engine side of the line.

Anyone have ANY idea what this might be?

[harrymaneuvers]

No check engine lights at all?

I would think that if you really are running that lean you would pop a IACV, O2 sensor, MAP code at the very least.

Running lean, if I am not mistaken could be from an intake leak between your MAF and the throttle body. Basically there is extra, un-metered air that is being introduced and messing up your Air-Fuel ratios.

I think this would pop a CEL but double check that the tabs on the air filter box are engaged at the bottom. If you have two air filter boxes I would be VERY suspect of the one closest to the throttle body.

[02_Legacy]

could be a bad o2 sensor, you need to hook up a scan tool to check this out though.

[Muse]

CEL is permanamtly on, due to some mouse-nommed wiring, but no new codes.

[harrymaneuvers]

CEL is permanamtly on, due to some mouse-nommed wiring, but no new codes.


Um... you have mice that have nibbled on wiring of the car... and it is not running well?


Can you clarify on what areas/wires were nibbled on by a mouse?


Also, post up the actual codes that you are pulling.

[Muse]

Wire to the knock sensor. I know they often go bad, but it's been replaced about 8 months ago. it's really, truly the wire.

And I can't remember the codes we pulled... I'll ask later.

[02_Legacy]

I would start by getting that fixed, whether it be a wire or the actual knock sensor. A bad knock sensor signal could be causing the symptoms that you are having.
Just out of curiosity, how do you know that it is running lean? Are you going solely on the symptoms or did you hook up a scan tool and look at the fuel trims?

[Muse]

Scanned it.

[1996Battlewagon]

What about the condition of the injectors?

[Muse]

Spark. Plug. Wires.

That was the problem... The computer was leaning the fuel mix to compensate. I feel so dumb. Two months trying to track a fuel issue, and it's this...

[r3v_v3ng3]

Spark. Plug. Wires.

That was the problem... The computer was leaning the fuel mix to compensate. I feel so dumb. Two months trying to track a fuel issue, and it's this...


It's all good. We live and learn

[Muse]

And it was a cheap fix, and two months of shitty performance makes normal running seem oh, so sweet.

Getting off the highway last night, kiiiinda too fast, I actually had to remind myself (out loud,) "It just accelerates better. The handling's the same..."