Technical occasional misfire - P0300 & P0340

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Technical occasional misfire - P0300 & P0340

se75

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Nov 9, 2010
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02 reg Mk 2 Punto 1.2 8 valve, 85000 miles, starts & runs perfect except what feels like a brief misfire now and again.

The engine misfires for maybe 30 seconds, and the yellow engine light comes on. Sometimes the engine light flashes and then goes out again when the misfire stops, sometimes it stays on (not flashing) for a day or two.

This happened about once a week for the last month or so. The codes are always the same, P0340 "cam position sensor circuit" and P0300 "random or multiple misfire".

Timing should be fine, the belt hasn't been touched since it was replaced 10,000 miles ago; so my initial thought was an ignition issue - replace coil pack & spark plug wires - or injectors.

But could the problem actually be the cam position sensor itself, let's say there's a bad signal coming from the sensor and that bad signal makes either the ignition or fuel injection play up?

Is there a straightforward easy way to test the cam position circuit?

thanks.
 
Zero the ECU codes then check with the engine cold and again when hot. If the sensor is failing its likely to be worse with the engine hot.

Also check the cable connector contacts are clean.
 
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