marcw

Been following this thread for a while, I've had very similar problems with my '06 FX4. Truck would jerk violently @ 40-50 mph, 1200 rpm. I was convinced that it was a coil, but the dealership had other ideas.. Replaced the Oil Temp Sensor, MAF, had me remove the K&N CAI, then FINALLY replaced 2- coils and no change. I decided to go this alone, and avoid the code chasers at the dealership; changed the fuel filter to no avail. This past weekend I replaced all 8 coils, and now she's running like the day I bought her.

Watch out for dealerships who know nothing about engines and how to diagnose problems, the jokers I went to were stumped because the truck wouldn't throw a code, CEL never came on.

Good luck, and DIY!

Renatta

05 FX4 5.4l. New plugs, new cheap Coils, Cold air intake, 3" flowmaster cat back single exhaust. 131,000miles. I get the bucking at low rpm's while trying to accelerate or go up slight grades, but, only when the engine is not totally warmed up. Runs perfect when at the optimum temp. Bucks very bad when cold and if I let it keep bucking it will trigger the CEL but then it goes out after a mile or so. Someone I work with suggested a temp sensor, where would that be located? Any help would be great! Thanks!