truckbed

2005 FX4 5.4L, 137k miles
ok ive read most of the posts for this issue. while cruising at about 50mph and in overdrive and heading up a moderate incline the whole truck shudders once or a few times until i press the gas enough to downshift into passing gear or whatever. I have read that it could be the tranny or a misfire. there has to be an easy test to determine which of these 2 it is... right?

I have bought a new COP ($40) and moved it around in 6 cylinders so far, others are hard to reach and I havent tackled them yet, but im losing hope and thinking it may be a bigger deal than a COP. I have read that the COPs start acting up when theyre hot and that is the only time i get the shudder. In the mornings i get right on the highway and try to make the truck shudder but cant do it until the engine gets hot. Could this rule out the tranny? I dont mind replacing all 8 COPs if im damn sure thats the cause, but I would like to avoid it if theyre fine.

I have read it could be trans fluid "breaking down" but i changed the fluid and filter no more then 12k miles ago.

i guess my question, should I keep switching out COPs? I know it could be more than one COP, but is there a certain symptom i can look for to tell if this could be either a bad COP or the tranny?

any help is appreciated!

ryguy

Have you replaced plugs and fuel filter? Just starting with the obvious.

GATORB8

Sounds like it's hesitating to downshift. My truck acted like that occasionally before I tuned it, the superchips tune fixed it. Maybe a dealer pcm flash would be enough to fix it, but by the time you pay for it, you may as well get a used tuner.

I'd say it's definitely a trans issue.

firems4289

My 05 XLT (5.4) did the exact same thing the other day. I was cruising about 55-60. Let me know what you find out.

bossman15

Pull all of your plugs and check for fouled plugs or cracked ones...I would put money on a bad plug...COPs are generally pretty reliable and that's not a tranny problem...my exact same symptom was a cracked plug in #5...should be throwing a code so take it to autozone and have them tell you what cylinder its in.

truckbed

im trying to avoid pulling any plugs because of the issue with them. the only time it shudders is when the engine is under a load in overdrive. I can floor it from a stop and its perfect, smooth as ever, but cruising at 45-55mph in overdrive and try to accelerate slowly or start up an incline and it does it.

I have read that the coils have 2 coils in them primary and secondary and when under a load sometimes they dont get the full charge to the plug. If it were a bad plug wouldnt it misfire during all types of driving?

bossman15

Yeah that is true but I would be 100 times more worried about the plugs...ESPECIALLY if they are the factory installed ones

KC5-0

Mine was doing the same. It was a bad plug and of course it was the rear passenger plug that was bad. Changed the plug and all is good.

ryguy

I can see why you want to avoid doing the plugs, but with that mileage on the truck I would bet on it being a bad plug. Mine had 96K on when I did the plugs and they were pretty wore out already. I am sure yours are really down there at 135K.

The plugs aren't "that" bad to do if you have the tool to a take out the broken ones. It's just time consuming, if you have any mechanical ability you should be able to tackle them. The rear passenger plug is a bitch!! I found that if you take the computer off the firewall and the bracket it opens that plug up more so you can get to it easier.

I am with most of the guys here, I would be blaming a plug before tranny or COP

bossman15

Yeah if it was a tranny or slipping clutch itd most likely be doing it through all speeds especially if you hammer it from a stop. Get those plugs changed ASAP and report back