My 2004 F-150 V-6 with 47,000 miles is back firing when I try to speed up to fast. It's OK if I'm light on the gas pedal but it will back fire if I try to step on the gas to much. The wires and plugs seem to be OK. Any Ideas would be appreciated.

 

VCT....? Cam Phasers? Anybody else? It sounds to me like your valve timing is off.

 

Your timing is off for some reason.

 

Have you changed your fuel filter lately? A clogged fuel filter can cause these same symptoms. The timming is controled by the engine computer so I can't imagine the timming being off.

 

The fuel filter is new. That was the first thing I did. I seems to be cylinder # 1. I swithed plugs and then wires and it stayed on cylinder # 1. The truck is orignal. Nothing has been done to it since new.

 

On the previous gen trucks with the V6 they had a coil pack. It sat up on top of the engine with the spark plugs wires originating from it. These would sometimes crack and coil performance would drop. I am not familiar with the 04' and up V6's, they may be different. Check it out, or maybe somebody will chime in and confirm if they are the same or not.

 

What smokinLUV said is another possibility to look at for sure, a faulty coil pack would cause a weak spark or no spark to 1 or more plugs. A faulty functioning fuel pump is another poss. area to look at too.

 

With it backfiring, the exhaust valve is still open during the compression stroke. It's not the fuel pump, it's a timing issue. Since it doesn't have a "distributor", and the spark is controlled elsewhere, I think it's a valve problem.

 

I have a 2004 f-150 with a V8 and it back fires and stutters when I accelerate with no load.
Anybody have any idea what it could be?

 

Jonny,

Unfortunately, your problem likely has little to do with the problem the OP had.

Something nobody caught here was that the OP had an '04 V6. Ford didn't put the V6 into the new body style until '05...meaning the OP had an F150 Heritage, which is the previous body style...

Any codes? Sounds like ignition or fuel delivery to me....

 

Somewhat unrelated, but I had this on my boat, 4 stroke Yamaha, it was a bad fuel injector. Just a thought.