Junius

Has the lean condition come back yet?

aTOMic

man I hate reading a long-*** thread about a problem which ends like this... grrr

You still here CWTech? (Last Activity Jan 2016).

Junius

Well to give some helpful info to the thread, I had a similar lean running condition last year that was very difficult to find since my 05 4.2 was driving extremely well. Doing all kinds of diagnostics from testing the MAF sensor to checking for intake manifold leaks, it was found that the right rear fuel pump was slightly causing a lean condition that was not significant enough to cause any actual problems. This was found after testing fuel pressure, which is supposed to be around 52psi, but after a few seconds on startup, it would occasionally/slowly drop to 46 psi, which was just enough to set a code but no actually give any problems. As a result, I replaced both the fuel pump and filter and the car has been code free for 8 months now. Hopefully this helps.

aTOMic

Thanks, Junius, I think I read your thread. I hope that's not my outcome (high dollar). Did you see how they tested fuel pressure for each pump, and for the fuel rail? I was told there was no fuel pressure sensors on our cars (BFM engine at least), but I find that hard to believe on a car with multiple sensors for every variable! I'd like to find it on VCDS if it exists.
I borrowed a nice brand-new FP test kit from O'Reilly's but none of the adapters fit the rail. Time to go to lowes I guess, then pull the pump fuses one at a time to see which is the weakling. I better do the fuel filter, too - that could diminish FP I think.

Junius

I'll definitely try to ask my mechanic how they tested fuel pressure. Good thing the fuel pump replacement wasn't as expensive as I thought. Fuel pump was $235 or so and labor was 2.5 or 3 hours if I remember correctly. This alongside the fuel filter.