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

What codes did it throw?

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

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.

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.

4.8iS is the N62

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?

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:

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??

And the DME is in the ebox - top, rear of engine bay on passenger side, correct? Where the IVM is?

The terminals can be dirty, corroded or even loose. Just visually inspect the terminal contacts and make sure they are not spread making a soft or poor contact on the MAF connector and on the DME connector. If you have an ohmmeter, check the continuity of the wires from one end to the other. It doesn't cost anything but a few minutes of your time to rule that out or validate an issue.

Same on what brand MAF you are using...I ran into a similar problem with my e39 when I was trying autopart/eBay Maf's. Finally fixed when I purchased an "OE" MAF from Range Rover. (back when they had the m62's in them and were $200 bucks cheaper straight from dealer) I would still check connectors/terminals as you may have a working MAF that's not sending the correct readings.

First, I think the fact that 4 different MAFs all give the same result means they're all fine. More likely for that to be true than for all to be bad.

When the MAF is unplugged, the control system figures out how to manage things (engine and AT) based on what sensors and system model it has. Many different ways to do something like this, not sure on specifics. But the fact that it runs just fine with the MAF(s) unplugged suggests the rest of the car is good. Engine, even the ECU.

Just a thought, maybe when it switches out of MAF closed loop mode or whatever it is, it also switches out some other sensors (e.g., O2 sensors) while it runs open loop. If you can get good info on how the open and closed loop circuits work, that may be helpful in deciding where else to look for the root cause.

On the connector / cable problem I suggested, I expect they are just wires. But for example, what if one of the (two?) pins with the actual MAF signal is bent / wire broken internally / etc. but other connections within the same connector / harness / cable are still good. Could it be that the ECU gets enough to think the MAF is there and working, yet it's actually getting garbage or no data on that line? Smarter fault detection methods could help in this, but maybe they kept it simple (for once, LOL).

So I would start with a careful visual inspection of the connector, making sure all the contacts look good. Then the easiest thing to do to check for a wire issue is to get the car running (with MAF connected, so running badly) and wiggle the wire as far as you can see it, hoping you intermittently restore something to make it run differently. Think about where an internal wire failure is likely to happen - at the connector, bends, any place it may have been pinched, etc.

After that, it's trying to find the other end of the MAF connector wires, and testing continuity through the whole wire.

Ok new update for today:

While researching “resetting intermediate levers”, I came across some other N62 owners with similar rough idle and hesitation issues. Several of them mentioned that they unplugged their VANOS solenoids and saw much improvement.

I figured it couldn’t hurt...quick and easy. Noticed a couple of the outsides of the solenoids were caked in oil residue and dirt. When unplugged I could see that the inside of the connections were coated on wet oil.

So I left all 4 vanos unplugged AND plugged back in the MAF. It runs!! Stumbled for a brief second at start but quickly smooths out. Idles great. Took it for one quick test drive and it ran awesome - no hesitation at all!

Sooo I think I might be on to something. Could have been the bad VANOS connection all along?!

I replaced all the VANOS last year. Must have not seated one correctly or have a bad o-ring. Going to clean the connections and retest. I can swap back in the old ones if necessary as well.

Stay tuned...fingers crossed!!

Nope. Mass air flow sensor measure the amount of air going through it. How does it do that? It's a wire (or a film) that's heated by electricity and the air passing through it will cool the wire down.

The DME can setermine how much air is passing through the MAF base on the temp of the wire after it has cooled down.

Unplugging the MAF and the DME default to a preselected mixture base on the engine coolant temp and the incoming air temp.

I know on a 3.0 M54 engine the MAF is a Siemens unit, and not a BOSCH unit. Cheap MAFs on eBay or Amazon are known to cause more problem than what you save on buying them.

Correct, the owner would unplug either MAF or valvetronic to get the engine to run until it warmed up. In his case, the motor would run ok once warmed up.


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FINALLY SOLVED!!!
 

Long overdue update to this issue that I believe I have finally resolved.


My X5 was parked for the last 2+ years at a buddies house - I bought a new car so it was a spare at that point. He is a part time mechanic and was supposed to be looking into this problem for me.


He never gave it much attention, so I got it towed back to me last Fall to continue troubleshooting myself. Then a month or so ago with the help of a mobile mechanic = we finally figured it out!!!


Turns out that ALL of the issues traced back to electrical/wireing issues to the components in the dry box in the engine bay. Specifically:



• Water damage/corrosion inside the DME/ECU, VVT and IVM modules. All looked fine from the outside. But once opened up they each had major corrosion to the circuit boards inside. So at some point(s) water was able to get inside that storage box and drench them.


Solution was to replace IVM module (cheap...already had a spare from previous troubleshooting), replace the VVT (cheap...used one from ebay) and had the DME sent off to "The ECU Pro" to be tested and cloned to a new module (not cheap... ~ $800).


• Various broken/missing/damaged/loose pins and plugs on the wiring harnesses for those modules. For example, IVM had some pins that were pushed in, VVT had a bent pin, DME had some female ends of the plug that were too loose/stretched open. All of these lead to them not making proper contact once the harness was connected. Probably all my fault when I was plugging stuff back in at different times years ago.



Solution was to repair pins by straightening them out and/or pulling pushed in pins back out. I also replaced the plug ends of 1 of them with a donor engine wiring harness that I already had - since a full engine harness swap was the next step on my list to solve (fairly cheap, ~ $250 used from eBay). I cleaned all the female plug holes in all of the harness plugs as well to remove any potential corrosion.


After doing all of that she started up and ran like a dream! 4 years after first starting this battle = I have no codes!!! :D


Several others had similar issues a few years ago when I first posted this, so I thought I would share my experience.

Congrats on the repair and good for you for updating the thread! :)

Haha that's AWSOME news for you! :thumbup:

Hooray!

Thanks for updating!

This is probably what killed the 4.4i that I got my aero kit off of. Symptoms sound identical. Had been at the shop (pretty good shop too) for a long time and they couldn't figure it out. Didn't concern me as I was just buying it for the kit... but it was a pretty nice 4.4i that I'm sure the owner wished he could have gotten back into good running condition.