Ford Truck misfire

[GreeCguy]

My brother has a Ford pickup truck, not sure of the year, 2006 or 2007, full size, half ton, V-6 automatic, 80,000 miles.

Cranks up, runs fine until truck is under load, (like climbing a hill with a bunch of stuff in the bed). When under load, it misfires very bad. He swears it's a broken plug which archs across the motor when under load, but it's hard for me to believe one dead cylinder would cause it to run that poorly. It's not like it's missing on one cylinder, but is erratic. It runs so poorly, it will slow down significantly, almost like it's running out of gas. I'm thinking it might be a clogged fuel filter since that's what it acts like. Anyone else have any ideas?

Secondly, once again, he swears the engine has to be cold to pull the plug. He says a trusted friend who works on motors says if he pulls the plug while the motor is hot, he runs the risk of stripping the threads in the head. Anyone ever heard of this before?

 

[GreeCguy]

BTW - where is the fuel filter located in a 06-07 Ford half ton truck? Please tell me it's not in the tank.

 

[DrDusty86]

I believe its under the driver's side frame rail. Should take all of 2 minutes to change.
Any codes?

 

[GreeCguy]

No codes. No flashing lights. Just a very bad misfire and loss of power.

 

[229]

Your brother is correct. When he replaces the Motorcraft plugs on a cold engine have him replace the plug boots also. If it is left misfiring it will take out the ignition coils and then the ECU which gets expensive fast.

 

[yonyon]

It may very well be a common ignition problem, but if this is a 4.2L there's also a possibility it may have clogged EGR nozzles. This presents itself as a multiple cylinder misfire under load when EGR is active. I'm not sure that year still had the problematic intake manifold design, but it's easy enough to check:

Disconnect the EGR and drive under conditions where the truck would otherwise run poorly. If it doesn't (note that it may ping or turn on the check engine light) run poorly it's time to clean the nozzles.

 

[Brons2]

I had the same problem with my 2000 F150 with the 4.2 and it was plugs. Unfortunately the first set of replacement plugs also had the problem, whatever it was, so after a visit to the Ford dealer, two of the plugs got replaced a 2nd time, then all was well.

 

[Rob_Roy]

Could be a bad plug, cracked boot, or a failing coil-on-plug. I had a similar problem with my F350 last fall, turned out it had several coils with cracked housings.

 

[patfan]

I have a 2003 with the 4.2. It has had misfire 2 separate times both times it was the coil pack.Happens when the coil packs get about 70000 miles on them

 

[RF Overlord]

Originally Posted By: GreeCguy
He says a trusted friend who works on motors says if he pulls the plug while the motor is hot, he runs the risk of stripping the threads in the head. Anyone ever heard of this before?
That's pretty much common sense for any motor with aluminium heads.

 

[GreeCguy]

Originally Posted By: yonyon
It may very well be a common ignition problem, but if this is a 4.2L there's also a possibility it may have clogged EGR nozzles. This presents itself as a multiple cylinder misfire under load when EGR is active. I'm not sure that year still had the problematic intake manifold design, but it's easy enough to check:

Disconnect the EGR and drive under conditions where the truck would otherwise run poorly. If it doesn't (note that it may ping or turn on the check engine light) run poorly it's time to clean the nozzles.


Yes, it is the 4.2 and yes, now that you mention it, that's exactly what it's acting like. The EGR valve on my 93 Ford Taurus went bad a few years back and it acted the same way - thanks for jarring my memory and thanks everyone for all the responses.

 

[SwampSurvivor]

Coil Pack. They don't seem to set codes on Fords for some odd reason.

 

[GreeCguy]

Originally Posted By: patfan
I have a 2003 with the 4.2. It has had misfire 2 separate times both times it was the coil pack.Happens when the coil packs get about 70000 miles on them


YIKES!!!! His truck has 80,000 miles on it and them thar coil packs are expensive!

 

[SwampSurvivor]

Yeah coil packs do odd things.

I blew a coil when towing with my dad's 2001 F350 5.4. It had no power under load until 3000 RPM - once it hit 3000RPM it stopped misfiring completely.

With no trailer, taking off in granny low, it had no problem. 2nd gear either. But in 3rd gear trying to acellerate or trying to maintain speed, it would misfire like crazy. UNLESS the engine was cold.

Idled perfect, in neutral with no load, it revved very smooth with no misfire.

The worst part was ... no CEL at all and no stored codes. We couldn't figure out what it was and brought it to a garage. They had seen it quite a few times so they knew it was a blown coil.

 

[donnyj08]

Sounds like a coil to me. Will it miss under a power brake? If it will have someone power brake it and disconnect one coil at a time, which ever one you disconnect and doesn't make it miss worse is the culprit. I've done this many times with modular fords. The v6 should be no different. After 100k it best just to drop a couple hundred dollars on a full set of new excell or msd coils. The coil packs break down over time.

Most of the time coils only miss under load, or sporadically. A real PITA.