I own a 2005 Ford Escape XLT, 4WD, automatic transmission, 6 cylinder, 3.0 liter engine. The vehicle has 120,000 miles on it. I am diligent about maintenance and following the owners manual.
Back in June I was on a trip and drove the vehicle around 2 hours non-stop in very hot weather (90 degree plus) at interstate speeds (75 mph). I stopped for lunch for around 45 minutes, and then when I got back in the vehicle and started pulling out of the restaurant parking lot, the vehicle began to buck and***** pretty bad when accelerating. I kept driving it, thinking it might be bad gas or a vapor lock issue. I got back on the highway, and after around 20 minutes the bucking stopped. It did this at varying speeds, from taking off from a dead stop to 55 mph. My thoughts about it later were either air or water in the gas line that worked its way out.
I did not have a re-occurence of the problem until about 3 weeks ago, when I was driving on a highway about 50 mph when it started again. This time it lasted around 10-15 minutes, then stopped. Last week I took it to my Ford Dealer and had the fuel filter replaced and the transmission flushed.
A few days later, the problem happened again, but this time it was not nearly as violent as the other two times, and only lasted a minute or two. I was going around 45-50 mph at the time. It seems that the new fuel filter may have helped, but has not fixed the problem?
The engine check light has never come on during any of this, and the vehicle starts and runs fine otherwise.
I would look at plugs and coils. It is an intermittent missfire.
A shop with a scan tool can look at missfire histories and verify the failure.
October, 22, 2011 AT 2:55 PM
I had the diagnostic computer checked. No error codes.
The spark plugs were replaced at 100,000 miles (20,000 miles ago).
If it is ignition coil(s), wouldn't the problem occur much more frequently? It always starts and runs fine outside of the 3 times that the bucking occurred.