Ihave camry 93, 4 cyl with 145K miles. All on a sudden few days back engine is vibrating or miss firing when it is not running. So when I start or stop on read light or something engine miss fires and car vibrates on and off. I took my car to a guy I know and he adviced we could start with Spark Plug. We changed all spark plugs, but didn't help. He asked me next thing to change plug wires, but this car has all of these changed (spark plugs, wires, dist cap, rotor etc) about 25K miles back. So, I decided not to move any further. When car vibrtaes my RPM gauge also moves.

One clue though, bottom of one of the spark plugs had oil little bit, other 3 didn't.

If I could find out the reason why it is happening, it would be really great.

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could be IAC, or TPS. possible cam position sensor. hard too say without looking at it, check engine light on??? also you might want too look into a fuel system service....hope this helps