316i M40 Misfire

Thu Jan 29, 2009 9:38 pm

I have an M40 316i with 70,000 miles. It snatches/jerks/misfires at certain speeds but not harshly and usually on a light throttle. It is worst at 40-50mph in fourth gear.

I know all about the camshaft problems with these engines and the cam was slightly worn so I had the head professionally rebuilt using parts from Motormec. The problem isn't as bad after the head's been donebut it's still there...puzzling. I've also checked the coolant sensor and replaced the plug leads, plugs, distributor cap & rotor arm.

Can anyone suggest where to go next with it?

Thanks

Fri Jan 30, 2009 12:10 pm

Fri Jan 30, 2009 12:19 pm

I don't know but my M40 does the same occasionally but only ever at higher speeds.

Fri Jan 30, 2009 8:25 pm

Have you looked at the TPS under the throttle body? They can get full of oil/crud and play up. I had an M40 like this. I carefully made a small hole in the middle of the bottom side of it. About 3mm across, and literally blew the crap out of it! It made a difference - in fact I got the tip off here. I think the oil comes from the breather pipe which vents into the throttle body. It then runs down the throttle spindle and into the TPS. A daft idea putting it on the bottom of the spindle in my opinion.

Fri Jan 30, 2009 9:16 pm

Yes, my local garage checked the TPS and pronounced it ok. Thanks.

Sat Jan 31, 2009 7:16 pm

Sat Jan 31, 2009 7:26 pm

DME relay? it's the white relay sitting on the bulkhead tray with another two... apparently they start to go with age...

asides from that the idle control valve is another culprit....my old touring would jerk every now and again because the ICV was unplugged (either that or have it stall at every junction when it was plugged in)...but if it happens at predetermined speeds that might not be the case....