RubyFX4

ive got a 2006 5.4 with 156k on it, runs great with no trouble except when climbing an incline or towing right before it shifts to 4th. It feels almost like engine knock or a gear slipping. I've been suspicious about a bad coil or plug but it hasn't thrown a code. The problem has been occurring for about 7 months and interestingly reared it's head right after I swapped the stock 17"s for 20"s and 275 tires. On another note I found a straight stretch of road and floored it to see if it would throw a code, I got my check engine light to flash but only for a couple seconds. Anyone have similar problems or ideas?

bourgeois1269

Just had the same problem for 6 months and changed all 8 coils. That's what you need to do. If you have original plugs go ahead and change those too. Get the COPs (coil over plug) from eBay. I paid $61.99 but spark plugs get motorcraft and not a knock off brand of plugs

gcwaterski

I've had this happen a few times, exactly as you described. Like a hiccup when I'm in the low rpm range & under slight load- sort of like when I am using cruise control going up a slight incline.

First time mechanic replaced the coil fixing the symptoms for a while.

Second time the mechanic tested & replaced MAF. This fixed symptoms for 3 months or so.

It JUST started doing it again over the weekend. I'm going to drop it by the mechanic today and see what it is this time. Not to hijack ur thread, but I'll be happy to post up what he believes my issue to be this go round, if that'll help. I too am open to any members suggestions as they are likely more knowledgeable than my mechanic on all things 5.4 lol

Jetdriver480

I had the same exact issue (usually on on-ramps while accelerating through 45mph or so). I replaced all 8 spark plugs and that fixed it.

bourgeois1269

I would get all new coil packs and plugs, I also had the same problem. I changed those plus fuel filter and awaiting on my new fuel pump driver module (FPDM) Wednesday

Jetdriver480

Ruby.... Get it fixed? If so what was it?