2004 f150 fx4 5.4

[tep98ws6]

I've been chasing around a few issues on my boyfriend's truck and I cannot figure out what it is. So it started with a random misfire - did plugs. Continued to misfire, did coils. Narrowed the misfire down to cylinder 6. Checked all the fuel injectors and all are functioning normally. Checked all wires and everything looks normal - now here's the fun part ... the misfire is so intrusive that power will cut out ONLY in 4th gear when it's attempting to downshift and it feels like it is chugging (and it will chug 4-12 times before it actually downshifts). I took the truck to the transmission shop that replaced the trans back in January on Tuesday and got it back today and they found no problem with it. Back to the misfire, during all this chugging, the #6 plug keeps fouling off and when I pull the plug, it's completely brown and burnt looking.

So I'm thinking it is electrical but it doesn't really add up to why it is causing the chugging and fouling the plug? Possibly the PCM? Anyone have a Ford truck with a similar issue?

[bamaz28]

im gonna say the problem is in the head, maybe a valve ????

[tep98ws6]

I found a TSB this morning on it concerning an updated spark plug + new coil pack ... I'm gonna try that first then do a leak-down test on the cylinder. Apparently, according to the TSB, if the plug doesn't do the trick then a new block is needed

[bamaz28]

TIME FOR A gm UPGRADE

[tep98ws6]

That's what I'm saying - he owes quite a bit of $$ on it ... but I told him if you need that new engine after we test everything ... it's still in running condition and still runs pretty good ... put that POS on craigslist for what you can get and get a different truck, lol

[bamaz28]

Tell him you want a 2500hd and packing a duramax lol

[tep98ws6]

problem found! new tsb was issued on updating to newest motorcraft plugs (that are $20/plug!) ... if that doesn't work, leak down test and if it fails? new block. JOY.

but happy i found it! none the less.