This is an issue that has had be perplexed. I'll start off with what I've already replaced shortly prior to the issue starting. I've replaced the PCV valve and hose, all coils and spark plugs, and the air filter. I had also briefly replaced the mass air flow sensor, but the one sent was incorrect for the engine and would throw a code at heavy acceleration. After a few months of driving the car, it began to rev for the first few stop lights after starting it in the morning, which has gotten worse. Now when you start the car, it will begin with a high cold idle, then quickly drop down, nearly stall while surging, then increase the idle, and continue this cycle. The only thing I've found to impact this is if you rev the engine to 3,500rpm a few times after it warms up a little bit. I don't consider this a solution and am very curious is anyone knows what this could be!
For reference, the car has 133,000 miles, and was not driven for quite a while before I started driving it again this year. I've put about 3,000 miles on it. I have the 3.0 Duratec, and have always gotten slightly to significantly worse gas mileage than I would expect (16-21 mixed), except for right after I replaced the plugs, when I got 23 on one fill up. The motor doesn't seem tired at all, and has great acceleration.
For reference, the car has 133,000 miles, and was not driven for quite a while before I started driving it again this year. I've put about 3,000 miles on it. I have the 3.0 Duratec, and have always gotten slightly to significantly worse gas mileage than I would expect (16-21 mixed), except for right after I replaced the plugs, when I got 23 on one fill up. The motor doesn't seem tired at all, and has great acceleration.