Really bad missfire and now it's fine... How come?

[anonymous-user]

About 3 weeks ago, my girlfriends Polo GTi suffered a really bad missfire, to the point that it just wouldn't drive. She tried to set off home from work one evening and it just spluttered loads and kept cutting out so she left it there. I went for it later and it was the same, horrific missing, reeked of petrol and virtually undrivable. Managed a mile in it before pulling over. Left it again as I went home for my towing bar. Got back to it and decided to try it again, so I started it and just 'revved the arse out of it', cue loads of black smoke and a really strong smell of petrol again and it started running ok again.

Ever since then it's been spot on again, and prior to the incident it ran perfect.

Problem is, I'm now not trusting the car and an worried when she goes off on a longer journey that it will break down again.

Any suggestions what might have been wrong?

It's a 2001 Polo GTi 16v with about 90k on the clock, standard engine, serviced about a year ago with plugs/oil/filters etc.

Cheers!

[Otto]

It could well have been water in your ingnition system somewhere. It can evaporate off once you get a bit of heat into the engine. Check your spark plug leads are sealing correctly and have no splits or cracks in any of the insulation or rubber boots. Also check the distributor cap if it has one.

I've found VAG cars very sensitive to grounding issues - make sure the negative terminal of the battery has a good ground to the chassis, and also that any other ground points are clean and free of corrosion.

[Diag]

Probably a coolant temp sensor. Quite a common fault and cheap enough to risk buying one.

[skid-mark]

they tend to suffer from faulty coil packs/ coils if it has misfired there should be a fault code stored in the on board diagnostics can-bus system, it will say some thing like (multiple misfire detectected cyl number 1).

[tegwin]

Did you get an engine light atall?

I had similar issues when the HT leads split... because of the way they are clipped into the top of the head, its really hard to remove them without damaging them... I would get a new set and a new coil from VW (NOT AFTERMARKET for those parts) and hope that prevents the issue comming back...

If you have access to VAG-COM you should scan for faults, it might highlight an error somewhere..