Low Compression Cylidner 5

Hey, Got a 2000 VR6 jetta. We ahve plenty of spark from plugs, wires, and coil. But we have a Po300 Misfire code that is in cylinder 5. I compression tested it and its read low compression at only 65pnds. However, the oil is dry, and it is not comsuming OIL or Coolant! WTF is the compression loss…? WE even tried lubing the piston with tranny fluid to see if the piston ring was stuck to the piston..but it still remains

any idea’s…

January 18, 2008 · Filed under Uncategorized

2 Comments »

  1. starrfyr Said,

    January 22, 2008 @ 11:21 am

    - Compression loss is usually due to either excessive piston ring wear, scoring on the cylinder wall, a “”warped piston”", or a blown head gasket. The fact that there is no coolant loss would tend to rule out the blown head gasket but it should still be evaluated because that’s what I think your problem is.

    I believe this to be true because you said there is no oil consumption. With worn rings, scored cylinder walls, or warped pistons there is almost always oil consumption. With a blown head gasket there is NOT always coolant loss. The portion of the head gasket that failed may not be in contact with a coolant channel and, therefore, no coolant would be lost.

    It’s a 2000 so I’m assuming 70k-100k in miles. This would tend to support a blown head gasket because unless you’ve beat the crap out of it you’re unlikely to see significant cylinder wall wear or piston damage. But, it’s a VW so who knows?

  2. Lester Said,

    January 23, 2008 @ 9:33 am

    misfire vr6 – sounds like burned exhaust valve,put air in the cylinder and see where it goes.

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