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Last week my 2002 Ford Escape started idling rough when the temperature was in the 30-40°F (-1°C to 4°C) range. It also seemed to have trouble shifting or something at 40-45 mph. I'd describe it as a stutter/shudder, and I could see the tach jumping up and down while idling in park.

I didn't have time to get to it until today, and it's in the mid-50s (about 10°C) now. There's really no sign of the previous problems. I turned the car on and let it idle, and I think I felt it stutter once, but then no other signs. The check engine light was still on and there were two error codes: P0401 and P0304.

After a bit of Googling, I think it may be an EGR problem (P0401) and subsequent misfire (P0304). I've experienced rough idling in tandem with the P0401 code before. I replaced the EGR valve about 6-12 months ago and that seemed to have fixed the problem then. I figure that the misfiring is a combination of EGR problems and the cold weather.

Is there something else that could be wrong with my car that's causing the EGR valve to go bad? Or did I replace the wrong component in the first place last time?

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Is it currently throwing a P0401 or P0304? –  hillsons Jan 24 '13 at 22:51
    
I cleared the codes, and I've driven it maybe 10-15 miles since. I experienced more of the stuttering around 40-45 miles, but it hasn't thrown another code. I just ordered a new Motorcraft DPFE sensor, since it seemed like a good relatively cheap first step. –  Doresoom Jan 25 '13 at 14:18
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2 Answers 2

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I replaced the DPFE sensor and have driven approximately 50 miles since without any indication of a problem. I'm theorizing that the DPFE sensor was the original cause of the problem, and previously replacing the old dirty EGR valve with a new one temporarily alleviated the symptoms caused by the bad DPFE sensor.

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Cold weather takes a toll on the engines, especially if it is running lean. Improper fuel feed to the engine may also result in rough idling, and it would be advisable to increase the fuel flow a bit and warm up the engine sufficiently before taking off.

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Please see our FAQ –  Larry Apr 24 '13 at 11:46
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