E36 318iS cutting out under load - suggestions ?

[vanHunks]

I have an 1997 E36 318iS that my daughter uses and it's been playing up recently, to the point that she's had to stop using it. The problem is that if the car is 1) warm and 2) is put under some load - travelling up a long hill, for instance - it cuts out completely and won't restart. Give it half-an-hour or so, it will starts as though nothing is wrong and runs fine for a short period until cutting out again.

Cold starting and driving around on flat suburban roads are fine - the problem seems to be connected to putting the engine under load.

It appears as though something is getting too hot and shutting down until it's at or below the "normal" temperature. The water temp is steady at normal and there are no signs of an overheated engine. There are no error codes in the DME.

It feels like a fuelling problem. I replaced the fuel-pump a while ago (although not the fuel filter) so I doubt the problem is there. The tank is half-full. Replaced the Crank PS around the same time and the CamPS a couple of years ago.

Any constructive suggestions would be welcome.

 

[wikked]

No harm in changing the fuel filterdepending on when last you changed it as it's relatively inexpensive. Cutting out uphill/under load does seem to indicate a fuel supply issue, maybe the FPR needs to be looked at as well

 

[bobbychoo]

Hmm my thinking is if it is the fuel system it will always be an issue. You saying that "normally" the car is fine, but under load or heat there is an issue. I thinking it could be vacuum related, or a air leak somewhere. How are the rubber hoses that feed the ICV, intake manifold etc. I would start here perhaps, look for tears splits in the rubber.

 

[vanHunks]

Thanks for the great suggestion, which as I discovered on Saturday appears to be the correct one. My experience may be instructive for others who experience the same problem.

I was on a test drive and as ever, the car came to a grinding halt going up a long hill. On a whim I disconnected the MAF and the car started and ran. I concluded I had a MAF failure. In the process of removing the MAF I noted a tear in the "boot" between the MAF and the manifold, adjacent to the hose-clip at the MAF end. I removed the boot and discovered several more cracks, the main one being on the inner bend of the concertina section, a completely open split, with an arc of about 120 degrees. It's a mystery the car ran at all.

I concluded (pure speculation - my knowledge of the DME is entirely generic) that the DME was receiving wildly inconsistent readings from the MAF and the post-combustion oxygen sensors and shut down the engine to avoid damage. Would it do this ? The car ran with the MAF disconnected because (I am told) the DME reverts to default values so is essentially ignoring the sensor information.

Anyway I'll install a replacement boot and see what happens. It does occur to me that disconnecting the MAF was a very useful part of the diagnosis process because doing so helps to isolate the problem.