Mike O.

While driving on the interstate in traffic today, I punched the car in fourth at about 50mph. The car was well warmed up with an oil temp of about 200F. Ambient temp was about 20F.

As soon as I punched it, the car lost a cylinder! The check engine light also came on (flashing). I happened to be about 2 miles from the dealer so I babied the car into the parking lot. Shut the car off for three minutes and when I restarted it, I got the same result (with check engine light flashing). A tech brought the car into the garage and got a misfire code on #2. He cleared it and started the engine - same misfire, same VAG code. He cleared it again and same result.

I left the car there. I called my mechanic who said it was smart to not drive it any further (especially since he is 40 miles from the dealer). His opinion is that it is either a plug, coil on #2 or a wire leading to the coil. He really doesn't think it's the ECU although I am going to stop by and install the stock ECU in the morning. The dealer immediately jumped to the conclusion that very well may be a cracked or blown piston!

I seriously doubt that a blown/cracked piston would throw a misfire code. I mentioned I want them to replace the #2 spark plug and move the #2 coil to #3 to see if the misfire moves to #3 with the coil. If that doesn't work I asked him to switch the lead to the coil to see if the misfire follows.

They are telling me they will figure it out their way (including pulling the head if necessary). The car has 120,000 miles on it and I don't want to pay the dealer to yank the head. Why can't they just fiber scope #2 through the spark plug hole?

Any suggestions would be appreciated on which way you think this is going. Any similar experiences would also be great.

Mike O.
98.5 A4 1.8TQMS
Hybrid K04 (diesel turbine/16G compressor)
Extrude honed/ported manifold
Wett software
TAP intercooler
TAP high flow cat/downpipe
Stebro exhaust
Samco hoses
Ram Air filter
993TT recirc valve
BIRA Stage 1
H&R/Bilstien
Neuspeed 22mm rear bar

Clark@turbo5.com

Check the plug and switch the coils like you said. Do not overlook the injectors. A bad injector WILL cause a single cyl to misfire. I doubt its a piston.


Clark

Geza

Your plan sounds good - also, a compression check will identify a blown piston

Electron Man

I hope dealer pride (diagnostic sequence they chose results in maximized chargable labor hours) doesn't hurt your wallet too bad...

Good Luck

RVTS4

Pistons are hard to kill, you would have been experiencing detonation before it happened and you would have noticed it. Sounds like a coil or injector problem. Pulling the head is just a way to make alot of money from you. Take the plug out and rest it on the block somewhere attached to the coil, crank the engine for a few seconds and look for a spark. If you have spark then its not the coil or the plug.

Dead

mechanic. You need to be clear when you leave the dealer what you will and will not pay for and make sure it is noted on the RO.

Žob

And come up as engine misfire.

Audiboy

before moving around parts. High HC's mean no ignition or low compression. Normal HC's mean no fuel in that cylinder.

If you have a vacuum (boost gauge), low compression on one cylinder will give it an erratic reading while idle (looses vacuum)

If not, the switcheroo and compression gauge is your best bet. Good luck