Update: it was a bad ground.

I used my laser thermometer to measure the temp of the exhaust manifold trying to find the dead cylinder. Cyl #4 was half the temp as the others so I unplugged the #4 wire from the distributor and the engine ran exactly the same. Before pulling spark plugs out, I took my spark tester and plugged it into cyl #6 ( to be methodical), and now the car was running good. As I was unplugging the tester and found burn marks on the plug wire. The ground cable was rubbing against the wire. So I electrical taped everything and rerouted the ground wire.

Illustration for article titled Update: it was a bad ground.
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Illustration for article titled Update: it was a bad ground.

Autocross on Saturday, misfire on Monday.

Felt like 5 cylinders this morning, lots of vibration. Surging idle. Rough revving up in neutral. Runs correctly under acceleration. Stutters when trying to maintain constant speed. Occasional backfiring.

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I’ll have to wait till after work to try diagnosing the problem.