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-   -   Only runs correct when no MAF is plugged in?! (https://xoutpost.com/bmw-sav-forums/x5-e53-forum/111087-only-runs-correct-when-no-maf-plugged.html)

fishhouse4 11-22-2019 04:49 PM

Only runs correct when no MAF is plugged in?!
 
I have been dealing with a rough idle and hesitation for about a year. My symptoms have progressed from minor to really bad currently.

In a nut shell here's what I'm experiencing:

• Really bad hesitation (like a shudder) for a few seconds only when applying light gas (maybe around 2,500 rpm and usually under load). Most of the time it is ok if you drive super slow with feather light acceleration and ok if driving it hard at WOT.

• This comes also with a very round idle. Minor sometimes...VERY bad at times - everything shakes and rattles. Sounds like it is going to stall out.

• Additionally, CEL lights with many codes. "Multiple misfires" (all cylinders), and "VANOS" codes. Clear codes and CEL stays off a few miles and then at one random time you give it gas and it hesitates they will all come back - in random order each time.

• Occasionally on cold mornings it will hardly accelerate at all. It just sputters and is barely drivable (is that limp mode?). I have to let it warm up, pull over and clear the codes and then it will run as described above - a hesitation only at specific times. I've learned to drive "around" it, so to speak.

Ok, now here's where it gets interesting! I've tried several things over the last 6 months to troubleshoot and finally gave up and took it to my BMW tech. One of the first things he tried was unplugging the mass air flow sensor. It was replaced last year, so I never even thought to look at it.

Magically, it runs near perfect with the MAF unplugged. I have since learned that it defaults to stored parameters if unplugged (it stumbles for a few seconds and then purrs like a kitten).

Great = needs a new MAF, right? Wrong!! I've now bought and installed 3 new MAFs and as soon as you plug one in = back to rough idle/hesitation/misfire codes. Unplug them = runs near perfect.

Ok, so wth is wrong when it does this when ANY mass air flow sensor is connected but runs fine without one???


FYI, I have done the following:

• Cleared codes.
• Smoke test = no air leaks.
• Die test = no oil leaks.
• Removed my Dinan stage 1 tune and restored stock.
• Removed foam air filter and replaced with stock paper filter.
• My mechanic reprogrammed it with a fresh copy from his INPA.
• Checked plugs and coilpacks (both new last year). VANOS solenoids new last year as well. MAF new last year.
• Cleaned fuel injectors (direct through the rail with cleaner).
• Replaced MAF (with 3 different new ones).
• Replaced integrated supply module (IVM).



FINALLY SOLVED!!! UPDATE INFO HERE: https://xoutpost.com/1236219-post18.html

crystalworks 11-22-2019 05:49 PM

What codes did it throw?

oldskewel 11-22-2019 07:38 PM

Could it be a problem with the MAF connector or wiring?

Overboost 11-22-2019 07:47 PM

What MAF sensor brand did you replace it with? There are a lot of horror stories out there with cheap MAF sensors. When you unplug the sensor, the DME reverts to Alpha N mapping (throttle vs. RPM). Plugged in it uses the MAF values. If the MAF was Genuine BMW or OEM then I would check connections at both ends (MAF and DME) and look for any physical damage to hoses or orings.

andrewwynn 11-22-2019 11:18 PM

Is that M62 or N62? i can't remember which is the 4.8; sounds a lot like the intermediate lever issues with the N62 motor.

what are the realtime voltage and g/sec readings from your MAF? get some control readings from other folk out here.

wpoll 11-22-2019 11:43 PM

Quote:

Originally Posted by andrewwynn (Post 1171996)
Is that M62 or N62? i can't remember which is the 4.8; sounds a lot like the intermediate lever issues with the N62 motor.

4.8iS is the N62

andrewwynn 11-22-2019 11:45 PM

on the N62 it will run like total shit if the I.L. get out of whack; they can either be damaged (there was a recall period a shit ton of the levers or eccentric i forget which were made wrong), or the lift minimum is set wrong. it's supposed to set itself from a power off, but look into 'reset intermediate levers' there is a key-sequence to do the job w/o software.

fishhouse4 11-23-2019 09:38 AM

Quote:

Originally Posted by andrewwynn (Post 1171999)
on the N62 it will run like total shit if the I.L. get out of whack; they can either be damaged (there was a recall period a shit ton of the levers or eccentric i forget which were made wrong), or the lift minimum is set wrong. it's supposed to set itself from a power off, but look into 'reset intermediate levers' there is a key-sequence to do the job w/o software.


And this would only show symptoms when the MAF is plugged in?

fishhouse4 11-23-2019 09:50 AM

Quote:

Originally Posted by Overboost (Post 1171980)
What MAF sensor brand did you replace it with? There are a lot of horror stories out there with cheap MAF sensors. When you unplug the sensor, the DME reverts to Alpha N mapping (throttle vs. RPM). Plugged in it uses the MAF values. If the MAF was Genuine BMW or OEM then I would check connections at both ends (MAF and DME) and look for any physical damage to hoses or orings.


All Bosch. That would be OEM, correct?. I've been through 4 of them now - and all from different sources (eBay, Advance Auto, Napa Auto, etc). It would be insane to believe I have had that many duds. :dunno:

fishhouse4 11-23-2019 09:51 AM

Quote:

Originally Posted by Overboost (Post 1171980)
What MAF sensor brand did you replace it with? There are a lot of horror stories out there with cheap MAF sensors. When you unplug the sensor, the DME reverts to Alpha N mapping (throttle vs. RPM). Plugged in it uses the MAF values. If the MAF was Genuine BMW or OEM then I would check connections at both ends (MAF and DME) and look for any physical damage to hoses or orings.


I will check the connections on both ends.

The only two ideas my tech had was a new engine wiring harness (which would address those connections you just mentioned) OR a new DME. Both are stupid expensive...

Ok, help me here...this is what I don't get about the wiring/connection possibility:

It's just a wire, correct? It simply transmits the signal from point A (MAF) to point B (DME). Like... all or nothing, I would assume. So if the wiring or connections were damaged, then the signal wouldn't go to the DME. Which would be the exact same as having the MAF unplugged. So I would think in that case you would not get MAF signals to the DME regardless of if it was plugged in or not.

Or are you suggesting that the wiring/connections could be damaged in a way that could somehow degrade or corrupt the signal from the MAF??


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