paintballdude05

I've done a bit of searching, and this seems to be a common issue, but I can't find a solution that really stands out and that I haven't already done.

I have a 2008 F150 XLT, 4WD, 5.4 Triton with just shy of 200k miles on it. Driving home last night, going about 50mph with my cruise on and in 4wd, the truck started to buck/misfire/surge going uphill. It's been pretty cold here lately and it was somewhere between -15 and -20 degrees Fahrenheit when this happened. The truck was fully warmed up and had felt great for the whole 20 minutes I was already driving it. I also just came back from a 600 mile trip with it and it performed pretty good too, this is the first time I have felt this. The truck was right in the 1100-1200 rpm range and the truck didn't kick down to go up the hill until I took cruise control off and took over the pedal. I drive the same route to work everyday and the truck hardly ever downshifts to go up the hills. This is the first time I have ever felt the misfire like this.

I have done a bit of reading, and most seem to attribute this to a spark issue and that would make sense. No CEL came one, which seems to be something common with these trucks. Heck even when my tranny was taking a dump there were no codes.

Here's what's been done in the last 10k miles or so.
- fully rebuilt transmission including torque converter
- new Motorcraft plugs
- new eBay coils
- new COP boots
- new fuel filter
- fairly new air filter (it should be clean, I barely go off road)
- resealed the air filter box with new foam
- IWE vacuum system has been cleaned with new vacuum valves and other parts

I saw a TSB describing a similar issue for 07-08 F150's. It suggested trying a intake cleaner like Seafoam (they suggested Ford Carb Cleaner or something?) and letting it get ingested into the intake via a vacuum port. I have never done this on this truck, and I know the previous owner wouldn't have either unless the dealer did it for him. I might just pick up a can after work and see if that fixes anything.

What are your thoughts on fixing this issue??

wolfy53

Exactly what mine did. I changed the plugs and all was well. Seafoam is great. I use it all the time on any small engine. One of those products that do actually work I think.

Since you already did your plugs, go look at your FPDM. It is up under your spare tire. It will be the only electrical box up there. They corrode and fail. You will have to remove your spare and then unbolt, 2 bolts, the FPDM. Remove it and check for corrosion. They aren't too expensive, under 100. Mine really wasn't too bad though. I just replaced it because I ordered the part before I removed to check in case it was really bad and break, then I would have been stuck.
https://www.f150forum.com/f4/fuel-pu...-yours-152908/

paintballdude05

That's interesting, I didn't know these trucks had this type of module. For a 2008 my truck is fairly corroded and was driven offroad a fair amount by its previous owner. A few months back when it was just starting to snow, the roads were really wet, I noticed that for a few days my fuel gauge would act weird. When I went to leave work in the afternoon my truck was telling me I had an empty tank, I really had 3/4's or more. Driving home it went from 3/4's to empty a couple of times, finally settling on empty. The next day the issue was gone but came back in the afternoon, then I was okay for the rest of the week. On the weekend I cleaned the plug, on the frame, under the drivers door since that was apparently a problem spot. It hasn't come back since though.

Long story short, would this cause my fuel pump to starve out momentarily?

bogeyrider63

If your plugs were bad and were having misfires, one of your cats may be plugged.

lewissa81

The FPDM could cause your symptoms. So could the eBay coils. Even a new plug can be bad.

paintballdude05

The original reason for changing out my plugs and coils was because I had a drivetrain shudder. That ended up being my transmission going, the engine was fine. However, when the guy started the truck after the tranny rebuild he forgot a vacuum line and the engine relearned it's fuel trims with a vacuum leak for a bit. I spent a weekend trying to figure out WTH was going on with the truck since it was bogging and spitting out gas from the exhaust. After resetting the PCM and going through a proper relearn procedure the truck ran awesome. I did go around 150 miles with the bad fuel trims before resetting the computer. This was over 4k miles ago though, I'd hope a plugged cat would have shown up before that.

I'm thinking it might be my coils, I ordered a set of 10 for this V8 just in case. I just don't want to start randomly pulling coils in freezing temperatures since I don't have a garage.

Would it be possible for a scanner to pickup a hidden (not displayed) code after the truck did the misfire but before I shut the truck off? As in, if I drove the truck home from work, it misfired, I hooked up the scanner before shutting down the truck and read it to see.

Thanks for the feedback guys.

TruckAT

[MENTION=153235]paintballdude05[/MENTION]

I'm a little late with this post, i know...

My '04 with the 5.4 engine had the same issue and as some others already posted it was solved after i changed spark plugs (the original ones) and COPs because we didn't know what of these were the problem. It threw code for misfire on cyl1 and shuddered when accelerating in OD or going uphill with a high low gear between 1200 and 1500 rpms.
They warned me to buy cheap plugs, so i bought the expensive ones ´

paintballdude05

You're not late at all!

I've got good plugs (Motocraft), but cheap coils. I'd just wish the engine would give me a CEL for which cylinder is acting up, or bank and the very least so I can start diagnosing. If it was the summer I would just slowly start replacing coils with the 2 spares I have. However, with it being nearly -20*C and it's not something I want to get into while standing in my driveway.

GigaFish

I'm not sure if you are feeling like spending any more money, but I was able to use the Torque app for my phone with a cheap amazon Bluetooth OBDII scanner to determine which cylinder my misfire was coming from, as it did not trigger a CEL. Torque is the most popular app for android, but I would assume there's an equivalent if you've got an iPhone. The App is $5 and the scanner was something like $9.

paintballdude05

I already have the bluetooth adapter, however I use it with my computer since iPhone's require a much more expensive OBD adapter and app. I guess I'll look into the software I have to see if it can spot the misfire like the torque app. If not, I might just have to borrow my GF's phone since she has an Android