pulling hair

[bkn4x4]

so by watcching videos ,using ob2 tester,i have come to the conclusion that Im still confused.
so after chasing a lean fuel bank 2 I have
!) fixed a few exhaust leaks
2) replaced all o2 sensors
3) tested fuel pressure
4) cleaned fuel injectors and rails
5) Cleaned mass air sensor.
fuel pressure 60lbs at idle 1500-2000 rpm 58lbs. when i drive it the fuel pressure maintains 57-59lbs with a OL
reading on both fuel banks. After 2-3 miles the fuel pressure dumps to 43lbs. then the fuel banks are in CL FAULT BANK 1 AND 2.
So tell if Im thinking correctly here. if I do get 60lbs from the fuel pump at idle this leads me to believe the pump is doing its thing. so is it possible im having a regulator issue?
oh and I am getting misfire on bank 2 cylinders only

[Schrodinger’s Box]

Sounds like your fuel pump is marginal, good enough to keep with fuel requirements at idle, lbut an increased load sees it falling behind down to 43lbs. My feeling is that regulator would be at fault at any engine RPM, this feels like a volume supply issue. If you set a steady 3000RPM without drivning it, the fuel pressure should decay, but bear in mind that high revs in neutral do not use as much fuel as under load.

[Apex]

This topic is pretty old now, but I just noticed that you posted about this issue in two different topics in two different forum sections. I would suggest posting all of your data in one place and if you’ve found out anything since.

Speculating based on your other post, your fuel trims are going crazy negative during your fuel pressure drop, compensating for rich fuel trims. It sounds like the fuel pressure could be dropping due to the fuel suddenly getting dumped into the engine, causing a rich condition and a fuel pressure drop. Maybe a sticking injector, which could be mechanically sticking or possibly even electrically. Is this engine’s fuel pressure externally regulated? That would be another potential source of fuel leaking into the engine, though I would think it would affect both banks.

One thing you could try is swapping fuel injectors bank 1 and 2 and see if your problem moves to bank 1, or at least this is the direction I would go suspecting a bad injector. However this may not be the correct direction as I can only guess based on what data you’ve posted so far.

[Schrodinger’s Box]

I had forgotten all about this one, but something has occurred to me – if your filter is PARTIALY blocked at the pump ( or if there is a PARTIAL obstruction in the fuel delivery system ) The pump can get the fuel system up to pressure but as the fuel is used from the delivery side of the obstruction, the pump can only gradually replace the fuel used. Look for the pressure building back up when you let it idle.

Thinking this through a bit further, as the fuel pressure drops and the engine injectors are being ‘starved’ the computer will compensate for this by extending the time length of the injector open. I’ve re read your original post about the fuel pressure dropping and this seems to ‘fit the bill’

To see this in real life, take the garden hose and just turn it on a fraction and watch the pressure build up slowly, when you let the pressure go at the other end it’s good for a bit and then the pressure drops to match the delivery rate.

Back to your car, look for somewhere the car has been jacked up and the jack lifting pad has crushed a fuel line, remember never give up you will get it fixed in the end.

[Apex]

Good idea on the partially blocked fuel filter, I remember watching a video about Volvo boat engine fuel pumps that were known to do this with paint chips from the inside of the fuel tank. Definitely quite a few possibilities on this one.

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