Gasit51

Hi Guys,
Got an 06 with the 5.4l. having an issue. Here's the scenario. Low revs (1100rpms) moderate speed 40~50mph high gear (OD) under load...usually going up a hill it starts bucking like it wants to downshift. If I add throttle it stops. It's almost acting like a coil pack is bad but past experience with that has been it keeps bucking. Could it be the overdrive switch malfunctioning? ( OD Off light does not flicker when this is happening). Tranny oil level is up and doesn't smell burnt. I don't have a code reader and am hoping someone has an idea of where to look. Thanks in advanced!
Gasit51

nickpatton_189

iTrader: (2)

Have you changed the plugs? Mine was doing this same thing and it was the plugs. Changed the plugs and coils and was all better

haha

As Nick said change the plugs.
Had the same problem in OD at 45 mph. It felt like the tranny was going to fall out. I drove with OD off to compensate for the problem.
I changed the plugs and the problem is gone.
I did not change the coils or boots. If the problem persisted that was the next step.

Try driving with OD off, unless cruising on the highway, until you have time to get the plugs changed. Dont worry, nothing bad will happen driving with OD off.
I drove with it off until I hit 55-60 mph then clicked it on.

techrep

iTrader: (1)

so do you have a CEL ??

MGD

Hi.

Those are classic random misfire symptoms - and they can and will occur during periods of peak cylinder pressure - just where you are experiencing them now.

As another mentioned yer CEL may or may not be lit but there will certainly be stored pending codes in the PCM. You'll need to get those pulled with a facility with an advanced scanner - the parts store scanners like Autozone can't usually do that. Even paying for a diag may be well worth it to garner this crucial info.

To avoid the undue expense of just blind parts-throwing, guessing at solutions, etc, you need to begin by providing those codes.

Lastly - it could be plugs, Cops or injectors (or something else more esoteric and less obvious) - further diagnosis will help nail the root cause.

Do it soon, as continuing misfires dump raw fuel downstream eventually destroying the cats and O2's, wash down cylinder walls and dilute yer oil. Delaying will only cost you more.

good luck
MGD

volsbear

I had an 06 Expedition and it did the same thing. Ended up being coil packs and plugs. Seems pretty common.

Gasit51

Thanks to all! She's due for a service so I guess I'll have 'em run the diagnostics while she's in there.
Gasit51

wolfy53

Mine did the exact same thing. It happened on my test drive. Truck had 98k miles on it. I made the deal contingent on them fixing the issue. I was going to have them change the spark plugs anyway. They changed the plugs and it has run perfect now a year and 17,000 miles later

Cutless009

I recently had my 05 (87K miles) in the shop. They replaced a ton of stuff on the motor, but told me she was throwing a misfire code under heavy load (high cylinder pressure) and that she needed the plugs changed.

I haven't been able to make it financially but my truck does the exact same thing under the exact same conditions and I was told by the guys at the shop that it was the plugs. I've got the plugs, just have to get them put in. Hoping this fixes the issue for me as well.

jamie930

Change the plugs and COP boots (only $22 more for 8 and you will have the COP anyways to do the plugs) and I bet it will go away