M44 misfire, 1200rpm idle help

[jmc330i]

My touring has just started playing up
Yesterday I first felt a small judder at part throttle around 2k rpm, which is annoyingly where it usually cruises at!
This morning it ran fine until the engine got up to temp, then the judder returned albeit more pronounced. On the way to work this evening, once warmed, it was full on kangaroo mode at part throttle. It ran ok with more throttle under load but still felt to be bogging down a bit.
The idle is around 1200rpm and smelling of fuel from the exhaust.

It was serviced about 3k miles ago and hasn't skipped a beat since, bar a failed camshaft sensor. It's a standard M44 but running M52 coil packs.

I'm wondering if a dodgy O2 sensor is a possibility?

Anybody with any ideas?

Cheers

[blazed]

I had a similar problem last year. It started to hold back at 2k then would jump past and run better at 4k but still badly and stank of fuel.
I removed and tested the DISA and it turned out it was stuck open. After a quick check on the part numbers I removed one from a m43 and fitted it and all was good. I also changed the pcv and valve cover gasket with the spark plug seals.
Also worth having a look at the spark plug holes to make sure there is no oil in there.

[Brianmoooore]

The more complicated an engine is, the more opportunities there are for things to go wrong, but the OP's is a perfect description of a failed/open circuit coolant temp. sensor. It's probably a four wire sensor on a M44, but the element inside is the same as the one in the infamous E30 'blue' temp. sensor.
Best solution is to read the ECU self diagnostics, of course, but in the absence of that, testing at the ECU plug pins is the same procedure as for any E30.

[jmc330i]

Excellent, thank you both. I was wondering about the DISA (as mine is quite noisy) but not sure it would cause the issue I was having.

Brian, I will try and get the codes read this evening. This morning the car ran ok, although it felt like it was surging on overrun while coming downhill (no throttle). It was quite a noticeable surge. Possible air leak somewhere?

[jmc330i]

Fault codes read this evening and apart from the many (expected) misfires that were thrown up, it also showed the throttle potentiometer. I think it was no voltage, but it was also the same on two other throttle pots.

The culprit, one snapped wire in the throttle pot plug...


One new pin socket, two minutes with a soldering iron, fault codes and adaptions cleared and the good ole touring is back at full steam