A few days ago my 2001 Expedition 4.6 (with 39,000 miles) started to "miss" a little. What I mean by that is if I was at a stop sign or accelerating the engine was a little rough - sort of like if you start a car on a very cold day and try and drive it immediately, but it is
100 degrees here.I guess I would descride it as a mild rough idle and slight hesitations as I accelerate. There doesn't seem to be any noticeable loss of power, but this model is kind of a pig with the 4.6 in it anyway.
Here is an interesting part: When I am at a stop sign and the idle is rough, if I shift into neutral the rpms jump a little and it smooths out real nice with no noticable misses. When I put it back in gear (with the brake on) the idle drops and it starts that mild missing again.
A day after this started, the "Have engine serviced" light came on. I drove it to my local repair shop (non-Ford but they have a diagnostic machine - $90 just to hook it up with no discount even if you have the repairs done there! Well, maybe that's normal...). They said the number one plug coil needed to be replaced. I said sure, as one of those went out at 20,000 miles and I had similar symptoms.
I also had them replace the fuel filter and change the transmission fluid and filter.
I pick up the truck after the repairs have been done, pay my $500 and drive out of the shop. After one block I can feel the truck is doing the exact same thing! I take it back and the mechanic looks at it and says, "Oh that's probably just your air conditioner making it do that." I turn the a/c off and the truck continues to do the same thing, the rough idle. He says, "Well, the guy who test drove it said the transmission was slipping, too."
He pointed out that he had replaced what the computer told him to replace and that the service light was off. Then he told me I should take it to a transmission shop.
Any ideas? I don't know that much about vehicles and I don't want to get taken for a ride at a transmission shop.
Why would a transmission cause an engine to perform roughy while you are at a complete stop? Is it possible that the new plug coil they put in is faulty? Would a new faulty plug coil cause the "Service Engine" light to come on immediately or not?
Any ideas or suggestions you can offer would be greatly appreciated...