Quote:
Originally Posted by MartinClan
Did a round trip of 70 miles today. Ok for the first 30 and then a breif reocurence of the problem and then it went away. However on the way home it came back big time and at one point I didnt think we would make it....
I have fitted a fuel pressure gauge and that told me the fuel was fine. However I now have another clue. This time I watched the rev counter. Each time the misfire appeared the rev counter started moving erratically. (Over reading....) The rev counter is driven dire tly from the ECU as I recall. So next thing to do is change the cpu i think. I have a spare somewher purchased just in case.
The saga countinues.....
Cheers, Robin
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Hi Robin,
sorry to hear you still having issues.
I think the Rev counter erratic behaviour is just a symptom of the misfire. Mine was very sensitive to noise and I suspect it's just picking up a lot of erratic pulses from the mis-fire. Sorry, I don't have any spare ECU's as I've now sold most of my e30 spares.
Whilst it could be a high temperature failure inside the ECU (dry joint or cracked PCB track) I still think it will be an input from a sensor that is driving the ECU crazy.
I guess the good news is that you have eliminated the fuel supply so can focus on the electricals.
I'd start with the cheapest things first and work your way through some simple things. You've changed the crank sensor, fuel pump and coil so those can now be assumed to be OK. I doubt it's the alternator as I think if that was faulty your red charging light would be coming on and I think you would have noticed that.
We are also looking for something that fails when it's hot and then 'cures' itself when it cools down? hhmmm.....
I think you said your plugs looked OK, but no harm in changing them all, just in case and to eliminate them.
Are your plug leads the original set from the donor car or did you replace them during the Sportster build. If they are the originals, I would invest in a new set but if they were new then leave those for now.
As Jim suggested, I think the rotor arm is worth replacing but try to get a good quality one. Personally, I wouldn't bother testing it as Jim suggested, I would just swap out the old one.
Water temperature sensors are notoriously unreliable. Usually they causing hunting or over fuelling but again worth a try as an intermittent failure might just be confusing the DME.
Throttle Position Sensor? - another fairly simple inexpensive sensors to change. Again, intermittent failure may be confusing the ECU/DME.
Finally, (for now) as your last failure was almost fatal, it may be worth another go with the code reader to see if anything has ben stored but I think the last time you tried it didn't have any codes. (Note to Jim, these early e30 BMW's had very limited code storage capability as it was pre-OBD I )
Good luck,
cheers, Peter