My truck (03 5.4L) is hesitating and bucking when I apply light pressure on the throttle while driving. I have changed the fuel filter, cleaned MAF, and also cleaned the throttle body because it started sticking. None of those things have helped.

I read that it may be a bad plug or COP. The truck has 79000mi and it still has the stock plugs and COP's. No codes have popped up either.

Should I go ahead and change out all the plugs and COP's?

Any other ideas?

 

Change the plugs - use Motorcraft platinums with NO antiseize and torque them to 28 ft/lb. That SHOULD fix it, if not, then replace the cops. Use dielectric grease in the cop boots.

 

28 ft lbs? That high?

I read that 11-13 ft lbs is where ford put them at.

 

Respectfully,,,, changeing plugs may temporarly clear the missfires due to a faulty coil that is 'marginal'.
After the plug for that cylinder gets some run time such as 500 miles or more the missfire will return.
It is a demenstration of how quickly a plug ages with use.
Ageing of plugs is the rounding/erroding of the center electrode and ground strap "sharp edges" such that spark does not jump the gap as easly and requires more coil voltage the marginal coil can't give so, the missfire returns.
Then you are still faced with finding the coil that is the basis of the original problem.
Good luck.

 

Is it happening at lower speeds like 45ish? like after you've slowed down?

Mine does it. occasionally. I dont think it's a missfire. At all. My 97 had a missfire & this feels nothing like it. Based on the speed & time that it does it on my truck, I would most likely say it's happening b/c the trans. is sticking in OD and when you slow down it doesnt drop out of OD then you gas it & she stutters b/c she's still in OD when she should be in 4th. Imagine driving a standard trans truck and being in 5th or OD and slowing down to 40mph then gassing it w/o dropping a gear... she aint gonna like it. Thats exactly how my truck feels when it does this stutter... Just my $0.02. My mother had a van that use to do the same thing. Had to replace some kind of sensor & that fixed the problem.

 

Mine used to do that, eventually found out the camshaft position sensor was unplugged by a mechanic who changed the belts.

 

To expand on the cause of the missfire gets a bit complicated as well as having had to run down this problem in the past.
At 45 to about 65 the EGR is called into operation.
This causes a very lean air/fuel ratio by design of near 20 to 1.
If one coil has lowered output, that cylinder will missfire on a random basis because it takes much more voltage to fire a lean mixture.
On decelleration, the throttle is closed and makes the mixture leaner yet for that amount of time.
Application of small throttle openings to a very lean mixture leans out even more and will fail a cylinder with poor spark and cause a stumble until you apply a large amount of throttle.
When the EGR is closed and more throttle is applied the mixture richens up and the missfire goes away until the next time you enter those specific driving conditions the missfire repeat all over again.
The cause of the missfire is a coil with 'shorted' turns that is not a hard fault so often does not set a code.
This coil fault can even show up as a missfire starting out from a stop sign or traffic light then clear.
The coils live a harsh life being on top of the motor getting the heat from the radiator and after motor shut down the heat from the exhaust manifolds.
None of this has anyting to do with the transmission.
Hope this is of help in understanding the specific issue.
Good luck.

 

^ Now that helps it make more sense than just saying missfire... Thanks!

 

I have learned that when you find a mis-firing coil, it's just easier to replace all of them, than to try and find the one bad one. Often they won't trip a code until your truck bucks like a horse, and once you change one, another will surely rear it's ugly head. I found some on eBay, for around $100.

 

One possibility to always be awhere of if you change all coils with new, used or some other make and there is a faulty coil in the new group, you assume the coils were not the problem if it didn't solve missfire, and become confused about what is happening.
A dealer will nearly always do a stress test to find the coil/s that are low in output.
You pay but they will get the one for sure.
Good luck.

 

Well I spoke too soon.... guess what happened on the way to work this morning

yep....................... Now mine is doing it.

Never fails. Getting married in Oct & trying to save for honeymoons and all that jazz... now got to drop DOE I dont have on the truck. *sigh*

 

If you use the factory torque specs, you are risking loosening and blowout.

http://blownoutsparkplug.com/faqs.htm

Read #51 and #52.

 

This is exactly what my truck is doing, it does it from a stop then it clears up if you give it more throttle. I guess I will be buying new COP's to go along with new plugs.