Truck running rough. on 2003 Ford F-150

My 2003 F-150 with 4.6 V8 is running very rough while under strain. Got back from Iraq and took it and had tune-up on it and it ran good then started running rough again and took it back and they changed out the number 4 sensor wire. Few weeks went by and started again. Don't have the money to take back so what do I do? It idles fine and aslong as your running at around 30 and 40 mph runs good you get above that it starts spitting, sputtering and serging.

by in Auburndale, FL on October 02, 2010
3 answers
ANSWER by on October 02, 2010
Do you know what specific codes were stored or why "number 4 sensor wire" was replaced? Was it an ignition coil that was replaced? The OE Ford scan tool measures actual cylinder misfire count which is usually a bad ignition coil or bad spark plug. The faster an engine runs the more it will "smooth out" that's why at idle or under load you may notice the poor running most.
ANSWER by on January 30, 2011
may be a little late, but had a similar problem with my '97 and it was a result of having a leak in the collant line hat would spray into the sparkplug well and short out a spark plug. Seemed to only happen at start-up with a warm engine or after truck ran for some time. Fixed leak all was good. Hard to diagnose with the engine warm the coolant would evaporate and everything look fine again.
ANSWER by on March 11, 2013
upgrade air intake and exhaust. could be the engine is not breathing properly. may want to reprogram the engine after also.
Related Items:
The engine is running to rich and the truck runs rough and the exhaust is cherry Red. their is no Catalytic Converters.
I have a 2000 Ford F150 with the 5.4L v8. I've had it in at my local ford dealership for repair and it still runs rough. Going down the road, once I reach the speed limit, the truck lurches and s...
Intermittent rough idle may be caused by the EGR sensor sticking, causing the EGR valve to stay slightly open. The valve and sensor must be replaced together to correct this concern.
my truck idles rough and my heater will not blow hot , but yet the temp. is normal so it's not...