SoCal AEB

my 98 a4 1.8t aeb is running like crap then running fine. I can't figure it out. getting misfire code on all cylenders with vag-com but no other codes. allot of the time it runs on only 3 cylinders so...

1st thing I did was to disconnect coilpacks 1 by 1 to find misfire. located at #2 so swapped coilpack, plugwire, plug, and fuel injector w/3 and still misfire at 2, so ordered an icm.
was running okay so I drove it while waiting for new icm, started acting up again and so I get out and disconnect #2 coilpack and It dies. the misfire has moved to #4. now I'm confused??? .

new icm arives and installed, still misfiring baddly then not. but every time I check where misfire is its on a different cylinder 1 2 3 and 4 at different times.???

I pulled fuel rail and injectors seem fine. could it be the ecu?

thanks for any reply.

ba2489

Crap that sucks when that happens I had the same problem but only when I put my car under heavy acceleration. I had to change my coil pack to the newer revised ones cuz supposedly I heard they were a recall. I have a 97 1.8T. Have u changed them?

SoCal AEB

No, they are the origonals as far as I know but I bought the car at 80k and it has 130k now. they do seem to give a weak spark but then it usually runs great, though it has been very slugish when cold the last year or so. maybe I'll change them anyway

ba2489

Yea at 130kms Its prob the coil packs. I changed all four on mine and kept old ones in case of a sticky situation. Our older model b5's are bad with coil packs. Since I changed to the revised ones, I haven't had any problems for 30kms. Good luck man

SoCal AEB

wow thanks for the fast re:
can anyone out there 2nd that motion?
my only reserve is that the misfire problem just started about 2 weeks ago and like I say it has been moving for cylinder to cylinder and don't realy want to buy new packs if I dont need them. I'm going to go out now and pull all packs and plugs out to check for visual spark.

SoCal AEB

Okay, cold started the car (about 28 deg outside this morning) started right up let idle and started misfiring after about 45 sec. so I pulled all 4 packs and plugs to check spark and it dosent miss a beat. if I didnt mention before it is a dead misfire when I disconnect missing pack there is no change in rythem of engine.
off to work I'll mess with it more tonight.

SoCal AEB

Okay, so I wanted to post the solution to this to maybe help someone in the future.
As most people know the cam chain tensioner is hydrolic and I think there was sludge build up blocking the oil lines alowing the chain to slack and misfire due to cam timing.
Last time I changed the oil I used some synthetic that claimed good up to 15k miles or some crap like that. So I havent changed oil in about 9 or 10k.
first I added 1/2 a can of seafoam to crankcase and drove about 30miles to break up any buildup and it instantly got better, put new filter and new synthetic oil and it seems to be running great.

as crazy as this solution sounds I hope it will help someone later.

emeth

how much that coil pack would be? and where to get it?

cheeba

The AEB engines are notorious for sludge problems - many 1.8Ts have died due to this. People with the early longitudinal 1.8Ts should be running only Group IV or V synthetic oils; and, should follow a reduced oil-change interval (OCI). An OCI of 10,000 miles (assuming miles since you're American) is destroying your engine. Don't follow the bottle; don't take advice of other people running the same oil in different engines.

If you have one of the small-sump 1.8Ts (~3.5 Litres), you should do the following:

- Run the largest oil filters that you can find; and, only a good German brand (Mann, Mahle, Hengst, etc.)
- Run Group IV or V synthetic only
- I would run an OCI of 5,000 KM, but the same distance in miles is probably acceptable
- Drop your oil pan and check out the sludge (you're going to want a long, wobble hex bit for this)
- Get an engine flush
- Run some maintenance doses of Seafoam shortly before your OCI