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Q: Running rough 2002 Ford Focus

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My 2002 Ford Focus SE. with the DOHC Zetec engine runs really rough and has loss of power. After running for a good while it will clear up and run smooth again, sometime after stopping and shutting off engine and restarting it.I had Autozone put on computer and there are no codes. I recently replaced PCV valve and tubing because hose was collapsing but this did not solve issue. My car has 116000 miles. My car has an automatic transmission.

My car has 116000 miles.
My car has an automatic transmission.

A: Hi - rough running can be caused by a numbe...

Hi - rough running can be caused by a number of things: misfiring, dirty throttle body, injectors, fuel filter, idle air control valve and so on. There was a technical service bulletin from Ford for this engine which pointed to replacement of the PCV valve, but you've covered this. If there are no problem codes, fuel supply, a coolant temp sensor that is reporting incorrect temperatures, EGR valve that is not closing completely, or a "slow" or lazy oxygen sensor are suspect as well. I would recommend an engine inspection by a mobile, professional mechanic, such as one from YourMechanic, who will come to your location, diagnose this problem, give you an accurate assessment of damage and cost estimate for repairs.

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