[Rhino]

I have an intermittent issue that is driving me to my wits end, making me want to get rid of my M5. I've exhausted all venues of troubleshooting the issue, and am coming to the collective wisdom of the board for assistance. See my sig for all the mods I've done to the car.


Symptoms:

Intermittent rough idling, then stumbling/misfire up until 4000 RPMs. After 4000 RPMs it's like nothing is wrong. No SES lights are triggered or codes stored when behavior is present.
​

Steps to troubleshoot:

Crank Sensor Replaced
All 4 CPS replaced
MAFs replaced
O2 sensors replaced.
Coils checked
Plugs replaced
Checked headers for proper fitment and cracks
DME replaced and recoded
​

I've ran DIS v57 multiple times, as well as Peake and PA-Soft 1.4.0.
A crank sensor error shows up occasionally in shadow memory within PA-Soft, and I've swapped the crank sensor out with a known good sensor. Issue persists.


A possibility I am considering is a bent tooth or other defect on my UUC flywheel, but need clear detailed pictures on what I may be looking for.


Any new paths or troubleshooting or guidance would be greatly appreciated.

 

[BrendanSC]

o2s? Changing pre-cats made a difference for me even though they looked clean and threw no codes

 

[Rhino]

Yup, replaced a few thousand miles ago.

o2s? Changing pre-cats made a difference for me even though they looked clean and threw no codes

 

[jfoj]

A few things that come to mind are Vanos O-ring, solenoid solder joints, Vanos gauze filters clogging the soleniod, bad soleniod, possibly throttle position sensor(s).

If I were you, I would either get the Vanos O-rings from BMW or spend the money for the Dr. Vanos kit, pull the Vanos solenoids, remove the filters if they are still there, re-solder the connections possibly bride the joint between the wire and the actual soleniod, cycle and clean the solenoids. Not 100% sure this will resolve anything, but you could rule them out.

Check out the TPS units, and see if they are suspious in readings.

As for the rough idle, this is not likely Vanos related?? What about the fuel tank breather under the intake plenum?

 

[jt2ma71]

Have you checked the distance from the crank sensors to the tombstones? I remember reading in the fsm about checking the clearence on the crank sensor.

Definately sounds like an electrical thing, perhaps a loose wire in a connector, when the car is running try wiggling connectors on CPS and CKPS sensors, MAF sensors, coils, see if you find anything. Id also check the TPS.

Good luck! these type of problems are nightmares to track down!

 

[ard]

So perfect test results when you ran the VANOS function test on a GT1?

Smoke test all vacuum hoses?

Skip looking for 'codes'...how about operating parameters? fuel trims, AFR, etc?

 

[vantaam5]

Not correct gapping of the crank sensor.Correct gap is 0.55mm+-0.2mm

Did you run Vanos test with DIS?

If this is ok,I suspect TPS on the way out...

 

[Wurger]

+1 for vanos related issue, I had the same symptoms when there was a broken wire going to a solenoid, it was still connecting most of the time and might even pass a test, depending on whether it was currently connecting or not. I did get codes but no limp mode, above 4k it ran perfectly all the time.

 

[ard]

above 4k it ran perfectly all the time.

I think that is because the default vanos position if the high rpm range- in other words vanos activates & moves cam timing under 4k to optimize lower rpm torque, and above 4k it is essentially 'locked'.

 

[vantaam5]

I think that is because the default vanos position if the high rpm range- in other words vanos activates & moves cam timing under 4k to optimize lower rpm torque, and above 4k it is essentially 'locked'.

There is a lot going on with Vanos changes in high rpms....did not believe it until I have seen the Vanos maps...

 

[cegeste]

Rhino hasn't run the VANOS test yet (we were short on time yesterday). He's verified the gap on the crank sensor a few times, each time while switching back and forth between the two sensors.

I don't recall if there was a component activation or function test module for TPS in DIS. Can search later (lots of threads with term TPS), but what's the best way to test (short of replacement) the TPS sensors?

 

[ard]

Yeah, I dunno... just hypothesizing.

 

[vantaam5]

Run the Vanos test when you find some times,guys...

 

[Rhino]

Run the Vanos test when you find some times,guys...

Thank you everyone! I am going to run the test tonight!

 

[Rhino]

What do you think? Bank 1 solenoid?

[

 

[ard]

Have you ever got into the solenoids? Pop them out, clean them good, replace the o rings.

I had performance issues yet no codes. My theory is that an 'electrically bad' solenoid will give you a code, but one that has crud in it, or leaking o rings are causing performance issues.

GL

A

 

[vantaam5]

^What he said.

Pull the solenoids,re-solder the joints,clean them,new O-rings...

 

[Rhino]

I am picking up new o-rings today and will service both sides.

 

[Rhino]

What should I used to clean the parts? Brake cleaner?

Should I lube up the O-rings?

what exactly do I need to resolder?

 

[Wurger]

What should I used to clean the parts? Brake cleaner?

Should I lube up the O-rings?

what exactly do I need to resolder?

1. Remove gauze filters or just their nets carefully
2. Clean with brake cleaner, activate solenoid and spray the hole from both directions for all solenoids
3 Solder red areas in pic, check main PCB carefully for bad connections
4. make sure the little pcb:s do not wiggle, otherwise there is a bad solder or broken wire
5. lube o-rings, make sure they seat correctly (no twists)

And I used the aluminium cover to push the solenoids in place with the 5 bolts, after which it is good to remove cover once more and press them by hand as they can still move a mm or so...


:cheers: