Seem to think Rob
@mrscalex had a problem with corroded contacts on the DME Paul. Might be worth asking him.
Tony.
I did indeed. That presented as a misfire on cylinder 4 for which I had an error code. It was traced back to a corroded pin on the DME responsible for sending the firing signal to the cylinder.
Now for belt and braces safety you need to know the background. That was after an engine replacement with a known good unit. I bought the car with a hole in the sump where the old engine had self-destructed. Putting 2 and 2 together the fault on the DME was responsible for the old engine failing from unburnt fuel raising the compression. So this DME fault destroyed the old engine!
So be warned! Unlikely your engine is at risk but it would be wrong of me not to relate the story.
As a routine step (and everyone should do this regardless) disconnect the DME and inspect the pins. Disconnect the battery first before you start. It's in the plastic box back left as you look into the engine bay. It feels like a scary thing to do but it's easy. Study the connectors carefully to see how to remove them - difficult for me to describe. But you need to push the pins in to swing the lock back. Look for obvious signs of liquid ingress while you are in there.
There's no need to sync the MAF to the DME (well not on a 2.2 anyway and I doubt a 1.9 would be different). But the engine might still be trying to reset it's adaptations to the new component. It will do that by itself over a number of miles. I don't think that would cause a misfire and I can't see how it would cause the DME fault. Those 2 faults may or may not be related.
I suggest you post the specific DME error code up here and also google, google, google for people discussing it on other forums (usually BMW non-Z3 forums with same engine/DME). There are people on those forums who are highly knowledgeable with the DME and child modules. That's how I tend to learn. You'll be lucky if someone pounces straight on it here.
You could try swapping plugs round to see if the misfire moves (dodgy plug) but you'll need to know which cylinder the misfire is on first. I'm surprised there's not a separate error code for that. The other common faults are the coil pack and vacuum leaks. Look high and low for the latter and consider a smoke test. Most Z3s by now will have perished vacuum hoses somewhere unless already replaced.
DMEs do fail. And anecdotally it's not that rare. But it's not straightforward replacing them as they have to be carefully aligned to the car. So don't go there with that one until you have to.
The only other advice I can give right now is approaching it logically. When I had my misfire I was getting ready to start pulling injectors out etc. But then I said, hang on, this engine was fine in the donor car. It must be something to do with the DME or fuel supply system which were the only components left over from the build of the car as I bought it. So what might have taken me for hours or never got found from working through a list of possibilities was result much quicker from being logical.
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