Ask Bob: VW Losing Power

by Bob DeP.

Dear Bob,
I have 1985 VW Jetta Car, which has about 120,000 miles on the 1.8 liter engine. The problem I just notice is that I am seeing a lot of black smoke coming out the exhaust pipe and I am also noticing a decrease in power when I accelerate. A couple of months ago I changed plugs and wires and rotor cap. What's wrong? Would a compression check tell me more? If yes to the last question , what thing am I looking for and what does it mean. Any advice would be most appreciated.

When doing a compression check, you want all of the cylinders to be within 10 percent of each other. If you have a low one, then it could be bad valves or rings. You would need to do a leak down test to further diagnose it. But, I think that the problem may lie with the computer. Did the check engine light come on? Has the oxygen sensor ever been replaced? The car may be stuck in a rich mode allowing more gas to be consumed than necessary.
Good Luck!
Drive Safely!
Bob, The Auto Answer Man

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