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Matt, Engineer
Category: VW
Satisfied Customers: 21991
Experience:  Mechanical Engineer with 20 years experience in the auto industry, 8 yrs in formula 1 engine testing
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I have a 2008 Beetle with a 2.5l engine. It is a long story,

Customer Question

I have a 2008 Beetle with a 2.5l engine. It is a long story, but basically it involves water getting into the engine area and causing misfires. In fact, at one point, the engine caught on fire and melted most of the wires. I replaced all the wires and coil packs but now I am getting a bad misfire in Cyl #4. Checked everything and it all seems OK. Did a compression check and the compression is all over the place in that cylinder. It seems to get much worse when the AC is on.
JA: How many miles are on the car? Is it a steady misfire? Or random?
Customer: is fairly steady but mainly random.
JA: Are you fixing your Beetle yourself? What have you tried so far?
Customer: I have done some of it, but I also have a friend who has a garage. he doesn't know much about VW's but he was the one who changed the coil packs and did the compression check.
JA: Anything else you want the mechanic to know before I connect you?
Customer: The car was involved in a bad accident a couple of years ago. The repair work wasn't done correctly. I've noticed a bad seal around the hood which is allowing alot of water to get in and pour directly onto the head. I've since fixed that but I wonder if that has contributed to the problem.
Submitted: 1 year ago.
Category: VW
Expert:  Matt replied 1 year ago.

if you're getting a bad misfire then its likely to be the variable compression I'd suggest to try squirting a little engine oil into the bore and then see if the compression pressure leaps up and is consistant then its a sticking piston ring or scuffed piston

if the oil makes no difference then its likely to be a burnt valve seat

and in which case can be repaired by removing the head with the engine in the car and then replacing the valves on the problem cylinder and recutting the valve seats

Expert:  Matt replied 1 year ago.


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