Take your car for a drive tonight, then pull in to your driveway and look. Make sure it's as dark as it can be. I chased a problem like this for a long time before I noticed arcing between the wires and the cylinder head. Ironically, I. Was dumping washer fluid in when I saw the spark.

Generally speaking, when it is a consistent stumble, it is fuel related. When the miss is completely random, it is usually spark related.

Keep in mind that 80's vintage cars need new spark plugs regularly.

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Eugene

10 E63 AMG
93 300te 4matic
07 BMW X3
14 Ford F-150 Fx2