I've got a 02 FX4 and have been having some problems with it bucking under acceleration. I had a similar problem a while back with it doing this when it shifted into 4rth gear. I replaced the plugs and wires, and it went away and I was happy as hell. But now, with about 1,000 miles on these plugs/wires, it is bucking worse than before, all the way through the gears if I am really on it.

I replaced the fuel filter about 8,000 miles ago. Could it use a new one already? There has never been any problems starting the truck, but I am not ruling out the fuel pump.

Also, there is 89,000 miles on the truck, coil pack maybe?

Help.

 

Is there any 'clunk' coming from the rear axle? I suspect the oh so awesome blowing up early model Torsen differential...

 

do you have a k&n air filter? or a fram air filter? a problem with these trucks i see at work and experienced on my dads truck is that if the air filter gasket isnt seated properly (most frams are too thin) or the air comes in through the filter with no restriction (K&N) it causes a voltage spike at the MAF which causes a "buck" symptom. just something to check. make sure that the air box lid is secured and the filter is sealing well

 

I really hope it's not the torsen. I do have a fram air hog drop in filter, but I have had it for quite some time. I will go check the seals on the box now, and then I am going to clean the MAF again to see if that helps at all.

 

put the stock filter or a motorcraft filter back in after cleaning and try that. the oil from the airhog could have gotten on the MAF or all the dust, pollen, bag ladies, small children and buffalo that the airhog lets through into the air intake stream

 

I'll have to pick up a filter tomorrow and try that out. Thanks.

 

My truck went though this fit, it was the air filter, I had used a fram air filter... i went back to motorcraft and the truck for some reason shifted alot better in the gears. I did not have the problem with the STP filter though... but that was a long time ago I used that.

 

my jeep was doing that to, so i seafoamed the **** out of it and it fixed it .. i think it was bad gas but meh it's fixed now

 

I switched the filter back and it helped a little. I lost my torx bit, so I didn't clean the MAf yet. I'm thinking that should help it out.

 

How do you properly clean the MAF sensor? I got a code on it yesterday...my truck was bucking a lot too, but I think I may have inadvertently fixed it when I took off the air filter hose to get to my pulleys that I replaced...

 

Go buy a can of MAF cleaner, unplug, unscrew, carefully take it out, spray it down, let it dry completely, reinstall. Just make sure to be carefull not to touch the wire that you are cleaning with anything, and also make sure that it is totally dry before you put it back in.

 

Just wanted to post back on how I got it to go away. I took the throttle body off and cleaned all the crap out of there, cleaned the intake tube, and the MAF, but it didn't go away. Yesterday I cleaned the IAC, gone baby!

 

Hmm that's interesting to me. Thanks for letting us know how you fixed it.