Ford F-150 Repair Question
Engine surges while idling
did you put in any gas line anti-freeze in to make sure their is no water in the gas for starters
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Hmmm?? strange indeed. Usually surging is caused by the fuel injection system adding fuel or air unevenly for some reason. Possibly the engine temp sensor might be flakey, and in cold weather it runs in its flakey zone. just a guess. I wonder if your car has a IAT sensor, (Intake Air Temp), some injection systems have these things. At idle the EGR valve should be closed and not working (unless being held open by carbon or something). It is possible that there is a vacuum leak near the injection unit that seals up when engine hot??. Sometimes just running some water from a hose at a trickle on suspect areas will cause a change in operation so you can locate the leak. Possibly there is a defect in the IAC (Idle Air Control) valve and it is hunting or something like that. If you have a MAP sensor make sure the vacuum hose to it is tight and in good shape, if the hose is soft and gummy, replace it. Thats about all that comes to mind without more diagnostics.
2 questions asked