V8 won't run properly, distributor question

[danny hoffman]

My 350i started to cut out the other day a I pulled the distributor cap to find that the rotor arm had risen up and was grinding away the cap.

After partially dismantling it the shaft clicked back into place and all appeared to be fine. The weights and the vacuum linkage are in their correct positions. Is there supposed to be a circlip inside the timing rotor holding it on the shaft? Mine just seems to have a plastic clip. I do have one on the outside of the shaft, but this doesn't stop it riding up about 10mm.

The car drove ok for about 20 miles it started to play up again.

So far I have changed the distributor cap, rotor arm, ht leads, - it seems to run ok for a bit and then won't idle or rev cleanly under 2000rpm.

I have checked for vacumm leaks, been through all the fuel injection tests - although I am 99% it is something to do with the ignition.

I have won a distributor, and ignition module on ebay - which I will pick up during the week. Any other ideas?

Cheers

Danny

[GreenV8S]

Is it the rotor arm rising up on the shaft, or the upper shaft rising relative to the lower shaft?

[danny hoffman]

The upper shaft is rising

[GreenV8S]

I don't think there's anything to prevent this, but the advance mechanism tends to resist upward motion and keep it settled down. I wonder if you have a worn bearing or something that is making the uppershaft whip inside the bearing and wind itself upwards?

[dw350i]

The small plastic ring that clips to the end of the inner shaft is to hold the upper and lower parts together. If it has any wear on it at all it simply does not do its job. More of of issue is the lower plastic retaining ring, if damaged (quite easily broken if the upper part is pushed back down when not in its correct alignment) by having its tiny lugs broken off, it will spin round at will and mess up the weights operation. Max advance will be more like 4 not 24 degrees or anything in between.