i have a '98 F-150 4x4 with a 4.6L V8. 78,000 miles so its got a ton of life left still. recently it has started hesitating really bad on acceleration. it does it all the time, but is most noticeable between 30-45 mph. going up a hill in town, i press down on the gas and it will shake and act like it wants to cut out, if i mash it, it will respond like it's supposed to. of a morning, when the trucks not completely warmed up yet, it will drive fine even up a hill. it only does it after ive been driving it for a few minutes or miles and its warmed up all the way.

i already replaced the spark plugs with motorcraft brand and i put on new plug wires too.

im thinking its the fuel filter or a bad coil but im pretty new at this stuff.

any help/suggestions would be greatly appreciated!

 

Are you getting any kind of check engine light? Go ahead and replace the fuel filter and clean your maf too.

 

nope no check engine light. it did come up a couple months back when i replaced the spark plug wires. i took it to a shop then and the code reader said it was a cylinder 6 misfire. replaced the plug wires and it drove just fine for about a month now its doing it again. inspected all the plug wires when i changed plugs a couple weeks ago and they appeared fine. im going to change the fuel filter this weekend and clean the MAF sensor and clean the throttle body as well. i will put on here how its working after that. thank a lot!

 

Be sure to use the maf spray as some of the other cleaners can damage it. If it isnt cleared up after that start checking for vacuum leaks.

Oh and throttle body cleaner, not carb cleaner.

 

ugh. I would do a transmission fluid/filter change. I'm working a similar problem and I think I have narrowed it down to TC shudder.

 

Check your EGR valve as it may be stuck. Clean it if necessary. You should be able to feel it move with the engine running and friend giving the accelerator a little gas. Be careful not to burn hand on hot engine

 

Has the check engine light blinked at all?

Doesn't sound like a fuel filter, - more like a coil pack or yea, the EGR Frank_Ford ford mentioned

Well yea, fuel first. Check pressure, change the filter.It could be the filter, you can get better flow thru 1/2 way plugged filter when get on it at times. But yea, fuel first, always..

 

nope the check engine light has never blinked or came on since a couple months back before the spark plug wires were replaced.

 

I would start simple and clean the throttle body and EGR valve and go from there. Only costs a can of cleaner and a little time.

 

Sounds like a ignition coil. Get going about 70mph and full throttle it till governor. You'll throw a code doing this a few times.