Missfire cured, credit where due

[Oliver Sedlacek]

My system had been suffering from an intermittent missfire for a stupidly long time, and I'd changed the Megajolt, EDIS, coilpack, VR sensor, plugs, battery and ingnition switch. As it had run for a couple of years without any problems, I thought substituting the faulty component was all I needed to do if I could just figure out which one. Recently the missfire got so consistent I decided to take it to Power Engineering (in Uxbridge) as they have a rolling road and experience with Megajolts. After trying a number of things the engineer tried disconnecting the alternator, and the missfire went away. As you might imagine, I was delighted! It seems that a not uncommon failure mode of alternators is that the rectifiers fail momentarily, putting short spikes on the battery cable. A multimeter wont show really short spikes, and the battery stays charged which is why I hadn't suspected the alternator.

It's a thumbs up from me to Powerspeed for solving something that had foxed me.

[brentp]

Good it was found. I'm pretty convinced Faulty / failing alternators are responsible for the majority of automotive electrical system noise!

[NITROPIXIE]

That certainly is food for thought and one fairly simple to diagnose by disconnecting the alternator.