X5 stalled/set codes while being inspected!

[X5chemist]

LTFTs -4 and +4 = 0 Basically perfect! Short term will bounce around based on idle, running, and WOT conditions. If short term stay between -/+10, it's good. You might have a little carbon build up. Drive it like you stole it! Blow out carbon out the exhaust! Driving it like a BMW M4 eventually stopped it from smoking. I6 like RPMs! I better start planning on a fuel pump replacement soon. Maybe after it passes inspection this year.

[workingonit]

I'm hoping to get the emissions monitors set and get the X tested before Sat Nov. 1, but there's a 7 day grace period afterwards, so I have some time to get the odd behavior sorted out.

I'm only concerned about the two times it semi-stalled and the STFTs swinging between +/- 28.5 under hard acceleration. Also, it once had a delayed shift (hung in gear) going uphill under hard acceleration. Never had any problem with the transmission before.

I'm hoping that resetting the adaptations will work miracles.

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[andrewwynn]

Under heavy acceleration uphill it's pretty normal to stay in the current gear up to redline depending how heavy your right foot.

If your dash gauge doesn't match fuel level, use test 21


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[andrewwynn]

Have you measured fuel psi yet? If it's over 50 FPR is shot and will cause rich mix and negative trims.

The MAF can send incorrect value to cause a similar problem also but I thought i saw you tried a couple different ones.


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[workingonit]

Originally Posted by andrewwynn

Have you measured fuel psi yet? If it's over 50 FPR is shot and will cause rich mix and negative trims.

The MAF can send incorrect value to cause a similar problem also but I thought i saw you tried a couple different ones.


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No, I haven't yet found the adapter I bought to fit the Schrader on the fuel rail. If I don't find it tomorrow, i'll order another.

Years ago, on 5-11-2022, when I measured pressure, it was

barely at minimum, IIRC. But, i didn't have misfires, hard starts, or long crank times, and only had the mysterious lean fuel trims (that everyone assured me was a vacuum leak...never found one).

Now, with a new fuel pump, and suddenly running super-rich, it doesn't look like a vacuum leak anymore.

What sort of fuel pressure would cause those fuel trims I'm now getting? and the surges of power, and/or the stumble/stall/limp mode following those 90 degree curves?

After using cheap $20 MAFs to combat erroneous fuel trim numbers (trying anything to do a workaround, since I never found the root cause of the lean trims), X5chemist showed pity for me and offered a proven-good, OEM Siemens-VDO MAF for me to use, at least until i could find the true cause of my lean fuel trims.

the Siemens-VDO MAF was giving me fuel trims that were much more normal, and I was quite happy with those numbers, and had thought that perhaps it wasn't a MAF problem, or even a vacuum problem, but maybe an injector problem (but why in both banks, with injectors only <5k miles old?), and I was using more and stronger fuel system and cat cleaning additives to try and fix the flow; I should've reasoned that the fuel system further upstream was the culprit.

[80stech]

The only way the fuel pressure regulator can provide more fuel is if the diaphragm is shot and then you will fuel going up the vent line to the intake boot, easy enough to check. The other only way would be that somehow the vent line is plugged and pressure is building up in the regulator, or you have that vent hooked to pressure somehow. If I had to throw out a guess I would say MAF. How do you have <5k on the injectors ??

[workingonit]

I'll check the intake boot tomorrow for fuel (coming up the vacuum line?), and use a pump to suck air or fuel up the line going from the F-connector to the FPR. We'll see what comes out.

The Bremi injectors were installed new by my neighbor during the 3.5 year period when he was refurbishing the X to swap for my Chevelle. I figure he might've put up to 3k miles on it, and I've just now passed 2k miles (in the 4.5 years I've owned the X)

[80stech]

Wrong or bad injectors would explain some things.
It might be pretty obvious when you pull that vent line off and gas comes out. To get an idea of how the regulator works put a vacuum pump (or a bit of pressure) on the line to the regulator while you are monitoring the fuel pressure and see how it changes.

[workingonit]

1) Was the new fuel pump pressure so much greater than the old pump, that it might've blown the diaphragm in the FPR (allowing/forcing excess fuel forward), or is it just a coincidental thing to installing a new pump?

Though I don't believe in GOOD coincidences, my life history is full of BAD ones, usually coming in threes. For instance:

• a) fuel pump replacement coming at the time I needed to get inspection, and now I'll be working on it for awhile to come
• b) had to bury one of our dogs on the same day, getting poison ivy at the same time...missing the young guy, and hating the poison ivy (I thought it was too late in the season to get it), and
• c) my new (4 months old) phone hasn't been charging for two days, but I finally fixed it, just now...is that three, or more?

2) After looking at multiple videos about changing a fuel filter/FPR on an E53, is there a way to squeeze under the shield/modify it, so that a crippled old man can do it while laying on plywood in his driveway? i would've already done the job three years ago, but it looked to be a bear, and I waited (perhaps too long). Not only is my fuel system paying the price of the delay, so is my body.

3) I understand how excess fuel could cause surging and rich fuel trims, but where does stumbling/stalling/going into a partial limp mode figure in? and only after a sharp turn or a sharp curve? I can't figure that one out.

[andrewwynn]

Ever fix your siphon jet and was fuel near 2/4-3/8 tank?


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