*UPDATE* - Rough cold running on M3 E36

Hi Guys,

All 3.0 M3's have a slight hesitation characteristic during the warm up phase, mainly around 2200RPM. This is a consequence of the combined effects of emission requirements and the VANOS operation. The severity of this "characteristic" can be greatly affected by outside influences such as incorrect valve clearences, throttle banks out of balance and individual cylinder mixture adjustment. These 3 items must be 100% before you go any further and should be done only by a BMW dealer, and preferably by a BMW technician who has been working on this engine since it's introduction and therefore received training in these areas.

Other factors which could also contribute to this problem are as someone suggested, coil problems (easily checked by BMW dealer using oscilliscope) - although I would expect faulty coils to cause worse problems when the engine is hot. Induction air leaks allowing unmetered air into the intake system - could cause lambda faults to be stored in DME and uneven idle when hot depending on severity of the leak - try spraying around the area where the inlet manifold joins the head with a little WD40 or brake cleaner when the engine is idling hot. Any variation in idle speed could indicate a problem in this area. Also, the throttle potentiometer should be replaced at every Inspection 2 service on the S50 engine and can cause all sorts of problems if defective. 

Finally, might sound like a silly statement but make sure all the basics are OK such as spark plug condition, air and fuel filters etc.

Hope this helps.

Andy.

Hi Mono,

No, this is not done at the time of service. It would push the cost of servicing through the roof ! Following the set up of the throttle banks the CO should also be adjusted as these engines have a tendency to "lean off" over a longer period of time. This is a dealer job. I carry out this on any E36 M3 if a customer is complaining of rough running. It's also a good excuse to check the throttle butterflys for distortion (More carbon deposits in front of one butterfly compaired to the other in the same throttle body) as this can cause additional running problems. Also a good time to replace the fuel hoses at the back of the block as these really suffer with the heat. Ensure the intake 'O' rings are replaced when the intake manifold is removed too.

Andy.

I'm in Jersey ! Sorry Man.

It's a 40 MPH limit - But France is only an hour away on the boat, my father has a house there, and they don't have speed cameras !

Andy.

Yeah, I take my VFR837R over for a good thrash now and then. Great roads and very little traffic too. You just have to watch out for those bloody French !

Andy.

Dudes..... me again!!

I am taking my car to Ajec racing in Gloucester tomorrow to have a look at my motor. The problem seem to have extended to when the car is hot now with a misfire at 2-2500rpm then clears at 3000rpm.

It has been into the stealers for a total of 8 days now and it aint fixed.....to be honest I would have done a better job of it myself.

Anyways, wish me luck at hopefully my problem I have had for 7months will be resolved!

Still not sorted, took it there today 180 mile round trip  oh yeah and on the way in the gales and pissin rain a stupid bitch decided to go into the back of me motor at the lights!!! her foot slipped off the clutch apparently!! luckily there was no damage!! feck knows how cos I went flying forward!

The car came back with 3 faults O2 sensor, knock control, carbon canister vent valve flap. There is nothing wrong with the O2 sensors cos they are new and also the knock control sensor triggers when the engine aint running right as well.

The guy reckons one of the coils is breakin down, didnt have any new coils lying around so tried a few second hand ones but still had the same problem but misfired differently! To be fair the guy was a nice dude and knew his stuff. I reckon it is the coils to......

So I ordered a carbon canister vent valve flap and 1 new coil, I am going to put it on each cylinder and see if it sorts it. The 6 coils are £300!! so I dont want to throw more money away!

christ knows how to fit that vent flap thingy just hope it is simple.

Why cant anyone sort me car!!!! I am ending up doin it me self again!!

Hi

Glad to see you are sorted at least that is good news.

Chris.