Eratic misfiring M40/B18 engine - anyone else?

[Jus07]

I've been to several mechanics with this problem and none seem to be able to help.


This problem is very erratic

A typical scenario is that car experiences misfiring / incredibly uneven firing for a period of 5 minutes (never when totally cold / usually anytime after 5 minutes of driving). I continue to drive and suddenly it then works perfectly for the rest of the journey sometimes the problem will vanish for a week or more only to return at a very odd time such as in the middle of a 2 hour motorway drive. When it happens if you stop and leave the engine at idle it splutters and revs to avoid stalling but eventually will stall.

-The misfiring can be quite severe causing the car to hop (at low speeds) if the clutch is not used.

-Higher revs helps to ease the problem.

- there are no faults recorded on the engine management system

-This can happen at idle or at very high revs, under load or not.

-Cold weather and long journeys the day before sometimes seem to be partial factors

My suspicions have ranged from:
-eratic air intake leak that his affected by air temperature?? I had the air intake -manifold gasket replaced and the problem seemed to go away for a while?
-eratic electornic sensor problems?

Has this happened to you or do you have any ideas what this could be?

Jus

[smc]

I had the same problem and took it to the dealership. The ignitor had to be replaced. It's a common problem according to the service rep.

I've been to several mechanics with this problem and none seem to be able to help.


This problem is very erratic

A typical scenario is that car experiences misfiring / incredibly uneven firing for a period of 5 minutes (never when totally cold / usually anytime after 5 minutes of driving). I continue to drive and suddenly it then works perfectly for the rest of the journey sometimes the problem will vanish for a week or more only to return at a very odd time such as in the middle of a 2 hour motorway drive. When it happens if you stop and leave the engine at idle it splutters and revs to avoid stalling but eventually will stall.

-The misfiring can be quite severe causing the car to hop (at low speeds) if the clutch is not used.

-Higher revs helps to ease the problem.

- there are no faults recorded on the engine management system

-This can happen at idle or at very high revs, under load or not.

-Cold weather and long journeys the day before sometimes seem to be partial factors

My suspicions have ranged from:
-eratic air intake leak that his affected by air temperature?? I had the air intake -manifold gasket replaced and the problem seemed to go away for a while?
-eratic electornic sensor problems?

Has this happened to you or do you have any ideas what this could be?

Jus

[Jus07]

I had the same problem and took it to the dealership. The ignitor had to be replaced. It's a common problem according to the service rep.

Thanks for your posting. When you say you had the ignition replaced. Do you know what they replaced i.e. I have replaced teh Ht leads and distributor cap and rotar arm but this does not seem to help?

[Damien1]

Hi I was wondering if you have managed to sort this out at all. I'm having exactly the same issue and finding it difficult to get a diagnosis/resolution. Local BMW garage haven't cured. I'd be interested if you managed to get any more info