I posted a little while ago about an intermittent problem with our 1.8T AGU engined Audi A3 which would occassionally misfire for a second or two and then be ok. A Vag-Com check for fault codes at the time didn't show anything up and as it was very intermittent I wasn't too bothered.

Anyway, it's got worse, much worse and it's a definite misfire. Luckily the other night I started the car and the problem occurred almost immediately (put put sound from exhaust, lumpy idle and a strong petrol smell) so thinking it's probably a coil pack I checked each one in turn and number 4 seemed to be the pot not firing so yesterday a coil pack was sourced and fitted last night. However, on the way into work this morning the damn problem has returned It only lasted a few minutes and then cleared itself but what the hell is up with it??

I checked all the wires to the coilpack aswell thinking it could be a loose connection but haven't traced them back to source yet. Another Vag-Com check hasn't shown anything obvious although I'm getting some strange lambda readings. Anyone have any ideas before I set fire to it?? :(

Perhaps a problem with the injector on that cylinder, or some electrical problem. It wont be a fuel supply issue I wouldnt have thought. The petrol smell will be unburnt fuel entering the exhaust system.

I'm a bit confused as the AGU doesn't have coilpacks like the newer 1.8T's ands has never been afficted with the coilpack problem. However it uses a seperate ignition amplifier mounted on the back of the airbox. First thing to try with this is give the contacts a very good clean and ensure the connectors are seated properly. This has solved similar problems for many people.

Eddy, so what's the big black box thing called on top of each spark plug?

Sorry, didn't mean it didn't have them at all, just they aren't like newer 1.8T's and as such very rarely go wrong. they are two parts. The part on top of the spark plug and the ignition amplifier mounted to the airbox with a heatsink inside the airbox. It's more common on the AGU for the fault to lie with the Ignition amp and then more often than not it's just a poor contact.

HTH

That's brilliant Eddy cheers. I shall check out the ignition amp later on and see if that's where my problem lies. Definately sounds electrical.....

The coilpack is very different to the one on my AUQ motor. Much larger with 4 x pins as opposed to 3. About double the cost aswell!!!

The AGU coil packs bolt on dont they?

Agreed with Eddy on the amp problem, and quite often they are intermittant aswell.

Yep, they're the bolt on type.... Have removed the ignition amp and cleaned up the contacts, checked terminals etc. Will have to run it for a while and see if the problem re-occurs.

Thanks for the input though