R57 misfire #3; Runs great w/out intake cam sensor connected; HELP?!
 

’09 r57 cabrio n12 all stock, no mods.
Head gasket blew @ 80k last year.
Head milled 2 thousandths, thicker mini h-gasket used. New TC, guides, sprocket and newest tensioner. Replaced h2o pump, plastic pipe and thermo assembly at this time.
Used Bentley fancy hardcover manual and lots of internet. Have rebuilt many h2o and air cooled VWs and many other fuel infected beast. This one is kicking my ass.
Runs great! Idles perfectly. That is until you turn it off and then back on. Obd II says misfire # 3.
Had a reputable BMW shop check it out post rebuilding head. Fuel rail pressure test, compression test with in spec. They said might be pvc (400.00) valvecover and/or #3 injector. Replaced both, no change. I have found that it runs really well with the intake cam sensor disconnected. Replaced said sensor and plugged it back in; runs like crap w/
#3 rearing it’s ugly head.
Today I replaced both vanos solenoids and connected the intake cam sensor. Idles great. Turn off the car and start it again. Runs like crap until I disconnect intake cam sensor.
With the car running great with the intake cam sensor disconnected, when I reconnect the sensor it continues to run well for a few moments, then runs like crap until sensor disconnected.

Seems odd that it will run great with the sensor unplugged, runs fine while sensor is connected but only for a short time.

I’ve done 3 minis, heads/TC etc, of the 2nd gen., this is the only one with problems....and it’s my personal vehicle.

Hope someone can help me figure this car out.
Will aka aRustyPatina

Failed to mention that coil packs were swapped to check misfire; misfire continued on #3.
Also, went through timing procedure twice to check if something was out of time. Nothing of note other than the above symptoms.
W.

Did you confirm having spark on cyl#3?
Did you swap fuel injectors and made sure they're pluged tightly?

@MiniToBe
Thanks for responding.
When I replaced the valve cover, I swapped coils and swapped injectors; tested new injector in cylinders #1 and #4. Put new injectors and coils back to original positions. Each time, regardless of placement, misfire cylinder #3 was the only code.
As to the spark to #3, how would you test for that, lol? That is so elemental that I ASSumed all previous actions would have covered that as an issue. Makes since however.....
Hmmmm, so when I plug in the intake cam sensor it may be interrupting power to #3!?
With sensor unplugged it runs Great. Thanks for your Help. W.

To test the spark, attach the spark plug into the coil pack. Use jumpering cables to place one end on ground and the other end on the spark plug. Let someone start the car while you look at the sparking.

When you disconnect the cam sensor, do you still get misfire on cyl #3?

Re: misfire while cam sensor unplugged
 

As to misfire while cam sensor unplugged. No misfire only cam sensor code.
Thanks. W.

This is very interesting...this makes me think you have one of two issues...either wiring or faulty DME. Can you buy an wiring harness from ebay and replace it. Any N12 harness will work.

Lol, my wife Loves this car, as do I. I considered it was the DME and cringed at the cost. Surely someone on this forum can reflash it!? Hope so. As to the wiring harnes, I’ve stared at it for a couple of hours. Wouldn’t be surprised if it were that simple. I’ll take a look on ebay and see what’s out there. My harness looks to be in great shape, but we know that’s often the case and therein lies the problem.
If you know/ can recommend someone who can reflash the DME, please let me know.
I really appreciate your input.
Will

I can put you in touch with my tech. He can clone your DME. Reflashing might not solve the issue because it is a hardware issue.
while looking for a wiring harness, look for good used DME that matches your part number. Check ebay and car-part.com
Pm your email so i can connect you with my tech.

Hey buddy, any updates?

Uhm......
 

I'm happy that it ran and sad that it stopped.

I assum you took the cover off and notated everything? Can you post pix of the top view?

Usually when the motor seizes, it is either the vac pump or the chain broke. I dont know if anything could've gone to the fly wheel and sort of jamming it.

What state are you in again?

This sounds very much like what I ran into with an N20 motor, so my story might (or might not) help - The N20 has a locking pin in the cam that allows to lock in a moved position (I forget if it is advanced or retarded) so that the cam is in position during cranking where there normally isn't enough oil pressure to phase it. About every other time we cranked it, the ECU thought the crank was out by 360* because the ECU we were using looked at the cam sensor for phase. The engine builder swore there wasn't a locking pin, so I fought that motor for two days before the locking pin was found. Assuming you even do have that sort of locking pin, have you looked at oil pressure? That can play funny tricks on the ECU during cranking since the crank sensor alone cannot tell if your TDC is a compression or exhaust TDC.

Yes, removed valve cover, but
 

?Locking pin?