Msifiring Problem ('01 GTI)

[Kaiser]

Car is a 2001 Volks GTI with the AWW 1.8t, stock K03 turbo and all, chipped. Don't remember offhand who the chip is from.

Problem is: At low/no boost, runs perfectly fine. Original problem occurred whenever any boost more than around 4-5psi hit the engine, it would cause a loss of power and a repeated misfire from the same cylinder.

We took the plugs out, checked for any problems, found none, and shortened the gap on the plugs to just slightly below manufacturer's spec's. Afterwards car runs solidly and pulls hard until you put the pedal down hard enough to reach 13-14psi and then causes the same rapid repeated misfires as one cylinder essentially stops firing.

I have a strong idea of what the problem is but I want to hear what some first-thoughts are from you guys in case I'm wrong about it, and to see if we're essentially barking up the right tree.

[stephen]

i have 2 ideas of what it could be. the first would be a bad maf. i've got a boxster, and when my maf was bad it was showing the same systems. after riding with the bad maf for about a day, the dme (ecu) finally put itself into "limp mode" and started shutting down cylinders. i'm not sure if you can do it on your car, but if the maf is bad on a boxster, you can unplug it, and it'll run fine (letting you know that's the problem of course). it's kinda weird, that's the first car i've ever known to do that...maybe it's an EURO thing....try it! my computer is setup to hold i guess..."standard values" that it will run off of, without the maf (NOTE: IT'S NOT A GOOD IDEA TO RUN LIKE THAT FOREVER IF IT WORKS).

i would also check your ICM. i have a buddy who worked at vw, and he told me that the icm is sometimes known to have issues. he said it's on the airbox, and they get wet a lot, causing them to short out intermittently (mostly with a lot of road vibration). he did say they usually have the dead cylinder at idle too though...not just with throttle response, but it'd be worth it to check. he said just try wiggling the plug at idle, and see if the cylinder you're having problems with starts acting crazy.

hope i helped-
stephen

[Kaiser]

You certainly gave me some other ideas, but like I said we had a good idea already, specifically the coil-over-plug spark system. He had two new coils and two old, replaced both the old coils and the problem is gone. The ICM wasn't the culprit because it's well hidden now, and the MAF was solid, but at least with your response I know what to expect next time. All's good, thanks for the help and here's some reps while I'm at it.

[99hatch]

I was going to say coil pack. Another think you might want to consider is get a new diverter valve if you havent already. I got one and it made a big difference of the stock one. Not really alot HP wise, but keeps the boost building up longer. I think they are only about 170 bucks or something along that.

[Kaiser]

He's got an aftermarket DV already, one of the ones off a Porsche Turbo if I remember right, it's ridiculously loud for a DV, sounds almost like a muffled BOV. He replaced the packs and says It runs great now, haven't gotten a chance to testdrive.