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-   -   "Pending" P030X codes, occasional engine misfire (https://xoutpost.com/bmw-sav-forums/x5-e53-forum/101938-pending-p030x-codes-occasional-engine-misfire.html)

Rookie48 12-30-2015 02:10 PM


Answers below... thanks!

Fuel pressure gauge was taped to the middle of the windshield (just under the rearview mirror), so my reading of it while driving may be slightly off. The fuel pressure gauge only moved on initial startup (truck had been off for at least an hour, lost some pressure attaching the gauge), It did not move move than 1-2 psi for the entire test drive, and when I shut off the truck, it remained at the 45 psi until the gauge was removed (about 10 minutes).

Hill at house has an initial slope of about 30%, was in 1st gear coasting, but applied a little throttle when misfire started. The hill is only 50 ft long before it levels out. I read somewhere that the DSC-X system can manage the "limp mode" but there was no actual wheel slippage (unless a bad sensor is creating a phantom issue here???).

Fuel pump was replaced by my local indie shop, I do not know the brand or where purchased (Hey Mark - if you are following this thread, feel free to jump in here! :thumbup:). The fuel pump was replaced after these misfire issues started as a possible cause. Fuel filter, regulator, and relay are all new. Pressure testing suggests the engine is getting fuel properly without any starvation issue.

I will continue to gather logs....

Thanks again!

jfoj 12-30-2015 03:04 PM

Is the misfire on the hill at your house consistent? Or random?

I am also starting to think maybe a flaky cam or crank sensor?

Does the tach do anything unusual just before the misfires start?

DSC should actually take away throttle, retard ignition timing, possibly apply or modulate brakes, but should not cause misfiring.

Any chance water has gotten in and around coils or injectors? I recall the E53/E70 has some issues with the cowl leaking onto the engine.

Do you have a lot of keys on your key ring? Maybe a flaky ignition switch, I know these are know to do funny things, but would expect to see other signs.

Just tossing some ideas out.

I am scratching my head on this one as well.

Rookie48 12-30-2015 03:40 PM


Same codes on hill as at highway speeds - P0300 through P0306 - they all get thrown at the same time. Sometimes it throws the codes as pending, sometimes stored, and sometimes it causes the truck to enter limp mode.

Crank and cam sensors were just replaced... tach does not react unusually when condition occurs.

I did not see any water or traces of water at the coils and/or injectors. I guess it is possible.. however the truck has the same issue in dry or wet conditions.

I have one key on the keyring - the truck key - that's it.

jfoj 12-30-2015 03:45 PM

Keep gathering data.

I may have you eliminate some PID's for faster polling at some point.

This is not looking like this is going to be an easy fix.

Rookie48 12-31-2015 07:59 PM

Another log, this time at much slower than highway speeds.

Was out for dinner tonight, short trip from the house. Left the restaurant, and threw codes and limp mode while cruising at about 45 MPH.

Diagnostic report (with freeze frame) and log attached. Log starts after the misfire codes and limp mode, but the truck ran like crap all the way home. Didn't misfire again, but stumbled and surged most of the way home (mainly from 6:01PM to 6:05PM in the logs). Tomorrow it will run fine (guessing, but that seems to be the MO on this truck).



Happy New Year!

jfoj 01-03-2016 09:50 AM

I have not looked at the latest logs yet, but what is the crank sensor history?

Rookie48 01-03-2016 05:55 PM

JFOJ, Others:

Crank sensor was replaced 3 weeks ago.

New logs attached again... in the first file I have captured the misfire (limp mode) condition where fuel status = 8. It is at row 647 in the log file. PIDS go to zero during a rolling restart to clear the limp mode condition. Second file has no limp mode, just here for reference.

I have been noticing the engine timing is always around 31.5 degrees when this condition occurs. That may not be an issue, I don't know for sure. I really feel like the engine has a vacuum leak causing the lean condition just off of throttle closed position at higher RPMs. Although it still can happen at lower RPM's, that is where I am normally driving the truck.

Smoke testing revealed nothing, but could there be a vacuum one-way valve that is closed under pressure (smoke test) but failing under vacuum?



SarTech 01-03-2016 07:37 PM

Watching this thread intently.
Hoping you find the fix, I think your fix will also be my fix.

upallnight 01-03-2016 07:56 PM

Do you look underneath the car when you perform the smoke test? There is a vacuum line that goes to the fuel filter/pressure regulator. It is the F connector that attaches to the rubber intake boot before the throttle body.

Rookie48 01-03-2016 08:03 PM

Going off what JFOJ suggested earlier in the post - and the only thing we didn't yet replace/inspect/clean are the fuel injectors. Could a single dirty/partially restricted injector create a situation where the cylinder is very lean, and the extra air pumping into the exhaust causes multiple cylinder misfires?

Since the truck idles fine, and typically runs normal (but not always, not always smooth running somedays, but not throwing codes or limp mode either), the injectors have been the last thing we are focusing on.


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