I'll get a new tester immediately.

The rough idle paired with the O2 sensor light coming on (nearly every trip), suggested to me that perhaps it was a burnt exhaust valve. I think I eliminated electrical by changing the O2 sensor, all the spark plug wiring, the distributor rotor and the ignition coil - all new - still running roughly.

Initially I thought vacuum. So I have been all over the vacuum system too. I have changed nearly every rubber connector - no change in the rough idle.

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Simon Shearer

1986 420SEL

2000 Porsche 911 Millenium Edition Carrera 4
2010 Lexus RX 350
2002 Kia Rio
2002 Hyundai Accent