Let's fix this thing. I'm back 2003 X5 3.0

[workingonit]

Before my fuel pressure tester broke back in the fall (at which time I ceased working on the X5, and started buying more parts and another tester), I was getting the usual 50 psi, but readings became erratic.

I don't know if it was the tester, or my cobbled-together extension hose restricting pressure, but the X was still starting instantly, though the readings were dropping.

I was having key and personal health problems in Nov 25, so I haven't yet hooked up the new tester since then.

Never had a stall or slow start before the original pump died, and the same with the new pump...just stumbles on turns.



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[Meestahbig]

Got in the car this morning. Fuel trims back to very negative. Right away, shortly after warm up. Went home and rechecked fuel pressure. 50psi and held for 20 min after shut off. Got back in drove 20 min, trims seemed back to good standing. No rhyme or reason.

[Meestahbig]

Drove around reading the 02 sensors. On 20 min drive back, I saw a few periods where the sensor went to 0v, didn't see this on the way out. Read it's not unusual if off throttle, could read 0v. Anyway, will swap both upstream with new Bosch.

How do I disconnect the plugs? Do I need to lift the small tabs?

[Meestahbig]

Ok, pulled both plugs apart. Easy. Connectors didn't looks dirty,.corroded or damaged.

[Meestahbig]

After unplugging and replugging in the O2 sensors (and spraying with electrical contact cleaner). I'm now getting basically almost no response from the sensors. 0v with the car running. Massive positive ve fuel trim like +27. And errors both lean and rich. Car still diles fine and drives fine. Scratching my head. Maybe something in the O2 sensor wiring.

[80stech]

Did you check/clean the DME connections, powers and grounds. contact cleaner can poison/ruin the O2 sensors if they are vented through the connectors which I think they are in this case.

[Fifty150hs]

Originally Posted by Meestahbig

After unplugging and replugging in the O2 sensors (and spraying with electrical contact cleaner). I'm now getting basically almost no response from the sensors. 0v with the car running. Massive positive ve fuel trim like +27. And errors both lean and rich. Car still diles fine and drives fine. Scratching my head. Maybe something in the O2 sensor wiring.

Check your MAF. I had a bad one and it threw crazy high fuel trims like you have.

[Meestahbig]

Yeah, mixed things online, but seems like both are now fully dead. I ordered new ones earlier today anyway, so be it. I only sprayed the sensor side, not the DME side. Let's see. I mean I've replaced basically everything else.

[80stech]

I think I said before, unplug check/clean the DME connector.