Got a misfiring '99 Vauxhall Omega 2.5.
The engine was smooth and stable until it was started last Tuesday when it suddenly started misfiring. At idle, it seemed to be ticking over on 5 cylinders. Being driven, it would hold-back, then surge repreatedly under throttle.
I took half the plugs out, and found the front o/s plug (whichever cylinder number that is) wet with petrol. I checked the lead against the block and there was no spark. I swapped the lead with one from another Omega, no change.
Dropped it into the garage, and they changed the plugs and leads as a matter of course. They connected the car up to their analyser, but the computer wasn't reporting anything wrong (no engine management lights on the dash either). They've done a compression test on the car, and all 6 cylinders are fine. They checked all the sensors with an ohmmeter and everything 'seems' ok.
The only thing they could suggest was the coil-pack, or DIS (which I'd thought might be the problem when I was getting no spark off the lead). They're going to change it over, but thought I'd throw t open to the group as well. Anyone come across anything similar? Would DIS seem to be the likely fault? Any other suggestions if it doesn't cure it?
I vaguely remember reading something about DIS firing in pairs? 1&5, 2&4,
3&6 or something like that. Wouldn't that suggest a faulty DIS would cause to cylinders to miss?I'll post a follow-up, hopefully tomorrow, as long as the new DIS has arrived.
Thanks, Paul