2006 M roadster rough idle

S

StinkyBeard

Member
I'm at the end of my rope here.

Started a rough idle 3 weeks ago.

Took it to the shop where they replaced 6 coils due to misfires on several cylinders. No change. Still throwing a MAF code, so they popped a new MAF sensor in. No change. Next they inspected the fuel injectors where they saw 4 that were clogged. 6 new injectors installed. No change. They finally used an auto tech computer to actuate the vanos which they said it failed 3 different tests. A second technician verified and both agreed a new vanos was in order. Since the computer wasn't throwing a code I said no and picked up the car.

Today, I sprayed everything down with starter fluid looking for leaks. Nada. I then pulled the air intake manifold and cleaned the throttle bodies and the idle control valve. All with no change.

So here I sit, throwing misfires on 5 cylinders and a mass air flow system fault but no idea where to look next.

Massive loss of low end torque and a really rough idle. Never stalls but the entire car rocks/shakes at idle.

Any suggestions?

Thanks in advance!
 
+1 on Smartbears suggestion just to get valves/rings out of the frame and position sensors which are not uncommon :thumbsup:

Ive had a blocked crankcase breather valve cause lumpy 'chuffing' at idle and severe loss of power on other cars, usually starts in colder weather and reduces a bit once the engine has warmed up. Caused by gunge in the unit or pipes and or a failed pressure valve, you might sometimes hear a whistling noise. Worth a vacuum test on the filler to eliminate it.

But whilst I can understand you being cautious about suspecting the VANOS after the tech's have basically swapped random parts with no result (other than a hefty bill) that must be worth checking further, a dynamic analysis should be giving precise data on which VANOS / cylinder is going down?

Anyway good luck and let us know how you get on when you get the oil off your hands 8)
 
I should have mention this is an M Roadster. S54.

Here are the codes is throwing:

2D06 air mass system
29D1 Misfire, Cyl. 5
29CF Misfire, Cyl. 3
29CE Misfire, Cyl. 2
29CC Misfire, several Cyls
29D0 Misfire, Cyl. 4

They did a leak down test which came back with no findings. 3% or something.

Is there an easy way to test a crankcase valve or best to just replace?

I've got a Bluetooth obd reader showing update hoping that will allow me to determine in real time if the timing is advance or retarding. Any other way to dynamically test the vanos?

Lastly, how would i go about testing the crankcase position sensor? Does that make sense with a air mass system fault?
 
Yep the fact it's an S54 may make a difference, I'm sure the M crew will chip in with ideas for you based on those codes,

Crankcase breather problems can cause too much vacuum so you may hear a whistling sound with the bonnet up, and feel suction on the oil filler cap and hear air 'whoosh' of air inwards when you take it off with the engine running. I've heard about people using a rubber glove over the oil filler to check if it's sucking in, or try the palm of your hand.
 
I read something about this last night. Going to give it a try today.

The mechanic who had it said that BMWs in general have a really rough time running with the oil cap removed. He said with mine, removing the oil filler cap made no difference which puzzled him.

From what I read, the balloon should slightly pull into the oil pan, but if its drastic then a valved is jacked up. Sound about right. Perhaps I'll try to shoot a video, since that seems somewhat subjective.
 
TBH the last one I had go was pretty obvious making it hard to actually get the oil filler cap off! In that case a slight blockage caused too much vacuum, in turn caused the breather pipe to collapse choking the breather completely when running. Definitely worth eliminating before shelling out on more parts.
 
Everytime you guys say something it reminds me of something else I've tried or uncovered.

Yesterday taking out the intake manifold I found a collapsed pipe going from the brake servo to the intake manifold. It goes through the 'sucking jet pump'. I tried to hit it with the kung fu grip and open it up but its too stiff to open up. Didn't want to risk hitting it with pliers.

IUXh1qQ.jpg
 
StinkyBeard said:
Everytime you guys say something it reminds me of something else I've tried or uncovered.

Yesterday taking out the intake manifold I found a collapsed pipe going from the brake servo to the intake manifold. It goes through the 'sucking jet pump'. I tried to hit it with the kung fu grip and open it up but its too stiff to open up. Didn't want to risk hitting it with pliers.
Click to expand...

um, not sure I know the kung fu (is that a snap-on tool?) and hit it with pliers methods :rofl:

I'd just assume a collapsed pipe isn't doing it's job and needs changing at the least, you never know it could be as simple as that (often is) :thumbsup:
 
Added a picture to the previous post.

FYI, the kung fu grip is immortal hand strength.

Hitting it with pliers merely meant squeezing it with pliers to attempt to open it up.

On realoem.com I'm not able to buy just that pipe. Is there any other place to source it?
 
StinkyBeard said:
Added a picture to the previous post.

FYI, the kung fu grip is immortal hand strength.

Hitting it with pliers merely meant squeezing it with pliers to attempt to open it up.

On realoem.com I'm not able to buy just that pipe. Is there any other place to source it?
Click to expand...

Just joking about tools and techniques,

Yep from what can be seen in the pic that pipe looks pretty flat, possibly vacuum collapsed and will be restricting things so will need to be eliminated. I'd guess it's part of a full service replacement unit which may include a vacuum valve? not sure, but if so the valve would be suspect so should be changed as a unit.
 
So, doing a little research on the sucking jet pump, it appears it only provides additional vacuum to the brake servo, not the other way around. If the brake servo provided extra pressure to the intake, it might have made since why it was throwing a mass air flow failure.

I ended up cutting 4' off that pipe and have it clamped to try to straighten it out a bit before reclamping and testing. I'm not hopeful though.
 
Got the kink out of the pipe. no change. Guessing my braking may be better now, but trying not to rag it until i get this idle and loss of power fixed.

Put a glove over the oil fill cap, with the cap removed of course. No suction whatsoever. Guessing that means a very sizeable vacuum leak, right? There should be some negative pressure, correct?
 
StinkyBeard said:
Got the kink out of the pipe. no change. Guessing my braking may be better now, but trying not to rag it until i get this idle and loss of power fixed.

Put a glove over the oil fill cap, with the cap removed of course. No suction whatsoever. Guessing that means a very sizeable vacuum leak, right? There should be some negative pressure, correct?
Click to expand...

As long as the vacuum pipe is not collapsing when the engine is spun up, and you haven't got either drastic vacuum sucking in air or positive pressure blowing out of the filler cap when the engine is idling then it's almost certainly OK and discounted as the cause of your issue. Someone with more knowledge of the S54 may step in here, but I think the S54 differs from the M54 N52 in having a non-pressurised sealed system, they run with a slight vacuum.

I think you can tick the crankcase breather off the list.
 
Well, figured I'd go for a long shot and tried running at idle without the air filter. I have a cold air intake by aFe (dry) and thought maybe, just maybe it was clogged up and not getting enough air. It made no difference.

Not sure what else to try. Only to take it to the dealership and start handing over crisp $100 bills :(
 
Dropped her off at the dealer this morning.

Got a call that I needed to replace the cold air intake.

Explained that I don't have the OEM intake and that I've put 8000 miles on the car since purchasing with no issues.

:(
 
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