Engine missfire

[swedishtony]

Hi People, this looks to be a very popular S2 site. I live in Sweden but from Uk originally. Worked for Lucas for 28 yrs on diesel systems. I used to help out on a site called AllExperts.com with diesel advice for 3 years before I moved here. Sad lack of diesel cars in Sweden so I have a 1994 audi s2 Avant German import. mileage high ( 270,000 km) but it has been well looked after and recently had an engine rebuild. I have had it 6 months without a problem. Unfortunately after a 50 mile trouble free journey I stopped for just one hour and then developed a missfire after restarting. I discovered by pulling off injector leads that it was No5 cyl. I got home and Left it for 20 mins max. started again and it run fine for for a while like 10 minutes again and started to missfire. When I checked if it was No. 5 it was now not that cylinder but No4, this time. This threw me a little( give me a diesel any time LoL)The previous owner who is family and very trustworthy came over the next day to check the plugs. The car was running really well that morning when he came. he removed just 2 plugs 4 & 5. He seemed to think they were okish but suggested changing them. He went and I drove the car about 5 miles quite hard with no problem. In the evening the car missed immediately on starting. When I checked it was still No4
I got plugs the next day and changed them but no betterexcept that now it does not make a difference on No 4 or 5 when removing the leads!! Water levels are ok and always have been. Oil is the same. No plumes of steam from exhaust. Cranking it with all leads off and listening for a difference in compressions seemed to be ok( used to do that with diesels to give a quick diagnosis) So now I am stuffed. no idea! if it was a diesel it would be in bits by now but i will have to wait for brother in law to help with this. In the meantime wonderful peeps any damn ideas on this, sorry to write such an epic but I am impressed at the amount of help that has been given on here and hope a little could come my way. Would it be possible for 2 injectors or igniters to go down like that. Do your best anyway, if more info needed please let me know. Not sure what else to provide. thanks Tony

[merlin's S4]

It's more than likely either a faulty coilpack or if it's definately heat related it could be one of the power output stages (POS). It may even be the wiring between the two. You can switch the connectors to the POSs (there are two) and if the missfire moves to another cylinder then it's a faulty POS! Do a search on the forum for more info and also see here http://www.sjmautotechnik.com/troubl...4_Ignition.htm

[blown_vr6]

Check the rubber insulators that run down the plug holes from the individual coil packs.
Mine develped a misfire due to a partially split insulator on no.2.

Pete.

[swedishtony]

possibilities

It looks like HT related as you guys suggest, it could have been the POS after the initial journey of 50 miles then heat breaking it down, but right now it is stone cold and missing and not improving when warming. But a POS looks a good try with one powering Cyl 5& 6. A coil pack was just suggested on the phone to me, Split insulators feasable but they look ok, you mean like tracking off a HT lead on other cars. This will cost by the looks of it anyway, look forward to investigation. Been a while since I was up to my elbows in it!! Thanks guys!
Tony

[swedishtony]

Missfire

Well I tried swapping leads over on the POS's and the missfire moved from 4 & 5 to 1 & 2 ! So good call. Waiting now to borrow one to try. Will let you guys know, thanks for the suggestions.
Tony