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  #1  
Old 06-20-2019, 07:41 PM
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rollinn95z is on a distinguished road
Slight Stumble at Low RPMs and Poor MPG - Many Things Replaced

Howdy and thanks for your time.

Newb here, but I am at the end of my rope. Have had an X3 for a decade which has treated me decent and decided to jump into a 2011 X5 35i N55 (2010 build) last summer with 50k from a BMW dealer in Florida.

Ever since I got it back to NC it has had a slight stumble/shudder at low RPM under load like when sitting stopped in gear at a light. It's temperature independent and more noticeable on initial startup. It has manifested further as bad fuel economy, barely 13-14 city and 15-16 highway. Most commonly would be classified and feel like an intake air leak or fouled plugs at the verge of stalling, but the intake system has been smoked twice with no leaks found.

Only at one point over the last year has it thrown a CEL which I believe was a P00BD "Mass or Volume Air Flow 'A' Circuit Range/Performance - Air Flow Too High". That prompted the replacement of the turbo as it was leaking oil and blowing a lot of smoke on start up. After having been pulled, the turbo impeller does have slop both along the longitudinal and rotational axis.

I've had the dealer, my independent, and a local German tuner shop look at it. I trust them all within reason and the dealer even sent a data set to the factory engineer to investigate. No one has definitively nailed this down.

The following parts have been replaced over the last year by the dealer, the indy, or myself in the following order:

ECM updates, plugs, vanos solenoids, fuel injectors, HPFP, coils, valve cover and gasket (leaking), water pump (failing) and thermostat, walnut blast intake ports, rear main seal (leaking), oil pan gasket (leaking), turbo (leaking at mid clamp), and most recently upstream O2 sensor.

Neither the MAF or MAP sensors have been replaced. When the oil pan was dropped, they discovered 3 sheared bolt heads and 2 sheared bolt threaded bodies originally from the front face of the vanos unit. That was "repaired" early in the life of the X5 with a recall, was double checked 2 years later, and most recently my indy checked that the vanos still had the bolts intact. The dealer never pulled the pan with the initial recall.

So, I've thrown a metric f-ton of cash at this thing and was ready to punt just before the CEL and turbo replacement. It has no current CEL; so remaining speculation could be a rogue sensor, clogged cat, tweaked vanos, or eccentric shaft gone out of tolerance.

Anybody want to hypothesize a cause or can refer a phenomenal BMW wizard in NC, SC, or southern VA?

Thanks and I appreciate the input!

-MJ
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  #2  
Old 06-20-2019, 08:46 PM
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Location: Columbus, Ohio
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Purplefade is on a distinguished road
Slight Stumble at Low RPMs and Poor MPG - Many Things Replaced

Just spit balling, but my initial thought was timing, leaning towards the Vanos, but sounds like youíve been through those already.. what about the Vanos oil return valves? Again, spit balling, but I know in my N62 a sticky return valve can cause all kinds of havoc with the Vanos function and at idle, under load, oil pressure is generally lower which may exacerbate the situation.

That said - I donít even know if the N55 has a Vanos oil return valve, but having the Vanos system it stands to reason that it would.

Man, if you were here in Cbus OH, Iíd have the wiz-bang Indy for you... donít know anyone in NC or SC though. But Iím sure the guys on here will!
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Old 06-20-2019, 09:31 PM
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rollinn95z is on a distinguished road
The only thing I see is for an oil pressure relief valve as seen in the attached pics. It's on the lower front of the motor; so I'll check it out. Bummer I can't get to your indy. Thanks for the input!

In the mean time, I bought returnable MAF and MAP sensors to try over the weekend.



Quote:
Originally Posted by Purplefade View Post
Just spit balling, but my initial thought was timing, leaning towards the Vanos, but sounds like youíve been through those already.. what about the Vanos oil return valves? Again, spit balling, but I know in my N62 a sticky return valve can cause all kinds of havoc with the Vanos function and at idle, under load, oil pressure is generally lower which may exacerbate the situation.

That said - I donít even know if the N55 has a Vanos oil return valve, but having the Vanos system it stands to reason that it would.

Man, if you were here in Cbus OH, Iíd have the wiz-bang Indy for you... donít know anyone in NC or SC though. But Iím sure the guys on here will!
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Old 06-21-2019, 01:25 AM
ard ard is offline
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ard is on a distinguished road
smoke testing is a really poor way to find leaks. Has someone looked at every hose, clamp and fitting into and around the intake?


Sounds like something was up with this car and it got dumped in FL. onto you. sorry


I seem to recall someone in your neck of the woods. Let me check.
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  #5  
Old 06-21-2019, 11:54 AM
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Join Date: Apr 2019
Location: Alberta, Canada
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Viktimize is an unknown quantity at this point
Rough idle when cold, with no codes, sounds pretty reminiscent of eccentric shaft actuator or sensor on the N52's. Not sure about it on the N55 though.
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Old 06-22-2019, 04:32 PM
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rollinn95z is on a distinguished road
As far as I'm aware, my indy looked at every tube several times. I haven't seen anything myself. I might try the propane method soon.

It was a double lease from the same FL BMW dealer, was a local car its whole life, and always serviced at that dealership. So I did about as much pre-investigation and good faith as possible.

If you come up with a good local, let me know. Thanks.

Quote:
Originally Posted by ard View Post
smoke testing is a really poor way to find leaks. Has someone looked at every hose, clamp and fitting into and around the intake?


Sounds like something was up with this car and it got dumped in FL. onto you. sorry


I seem to recall someone in your neck of the woods. Let me check.

Last edited by rollinn95z; 06-22-2019 at 05:41 PM.
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  #7  
Old 06-24-2019, 09:18 AM
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Location: Alberta, Canada
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Viktimize is an unknown quantity at this point
Quote:
Originally Posted by rollinn95z View Post
As far as I'm aware, my indy looked at every tube several times. I haven't seen anything myself. I might try the propane method soon.

It was a double lease from the same FL BMW dealer, was a local car its whole life, and always serviced at that dealership. So I did about as much pre-investigation and good faith as possible.

If you come up with a good local, let me know. Thanks.
Smoke is a great tool when used correctly. But I've seen mechanics pull vac hoses off and shove the smoke in there in an attempt to see where it starts leaking out of the intake tract. Unfortunately a lot of these leaks don't show themselves until they have vaccumm on the system. So a lot of times it is better to run the vehicle, and then move the smoke wand around until you see it being pulled in somewhere.
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