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Ford Focus Zetec Estate losing power and slight knocking when at standstill.

Been driving an X Reg Ford Focus Zetec for last five weeks. No problems until now. It seems to be missing or losing power a little and slight knocking when at standstill. Is this a cylinder problem or computer problem? It's done 165,000. Not sure of last service but MOT until next year.

Asked on 18 September 2012 by Bryan

Answered by Alan Ross
Assuming that this is a Petrol engine it could be a number of things. Does the engine misfire when under load, i.e. accelerating? Is the knock more pronounced when accelerating? Does it misfire at all when just driving along at constant speed?

Firstly, check all air/vacuum pipes for any leaks.
Then check the MAF (mass air flow) sensor.
Then check the ECT (engine coolant temp) sensor.
Then check the (H02S) heated oxygen sensor(sometimes referred to as the Lambda sensor).

You may want to carry out a compression test (given the mileage).

Also the injectors should have been serviced at approx 100K (have they been checked /serviced at all?)

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