ok i give up, what could it be? My truck just started skipping a little one day, felt like a coil going bad. Having lost 2 coils in the past i knew the feeling so I went and got a new coil, and started replacing them. I’d remove 1, put the new one on and go for a ride, still skipping, come back, take the 1 I removed, and swap it for another knowing the bad one was still there somewhere. Well I’ve gone through all 8 and it’s still skipping. Also it runs ok at higher RPM, ( 20 – 40 mph with the OD off ) I can feel it now and then, almost like an older car with an arcing plug wire, but get up to highway speed, OD on and it really skips, obviously completely dropping a cylinder. I really can’t afford the $200+ the dealer will charge me to just Diagnose the issue. Truck has 5.4 w/115k on it, plugs changed last year and I also just change the fuel filter to see if that helped, no luck. It may be coincidence but it seems to do it worse if it’s raining out but maybe it’s just me driving slower.

 

What's skipping mean?

 

hop on one foot while moving forward, then put down other foot and pick up the first ....oh wait, JK
It wll run fine then out of the blue, 1 cylinder isn't firing. I'll get a good chug chug and either get off the gas, or shut off the OD to raise the RPM and it goes away. real bad at highway speed or with a load on the motor. not too bad crusing along at 30+/-

 

interesting...just went to get gas and it's running very very rough now. Step on the gas and it shudders and hesitates very badly, no power and still feels like an electrical arc somewhere draining power. It's very warm out today, mid to upper 80's. Cool and raining this morning on the way into work and it ran ok, not great but much better than it is now. ...coincidence or another symptom.

 

Injectors? No cel? Does it miss at idle?

Try running some seafoam in the tank per ratio on the bottle. I normally wait till I only have about 1/4 tank, then put in how much needed. That way you don't use up a whole bottle in a full tank.

When was the last time you changed the fuel filter also.

 

Is the check engine light (CEL) on? If so, see if you can find someone to read the DTC code(s). Sounds like a misfire, which doesn't always trigger the CEL but could also be a myriad of other things. Autozone used to read the codes but I heard they don't anymore. I think you can get your hands on a code reader for about $60.

Sounds like a plug - COP issue. When one goes bad, the others seem to follow suit. I'd replace all the COP's; you can get a set of 8 for around $80 from global auto or uneeksupply on ebaymotors.

What kind of plugs did you use?

 

i was able to limp home last night, now it's runnig very rough at all speeds. no power and i had to be gentel on the gas to slowly get it up to speed, thought i was going to be calling tripple A. on the way home the service engine soon light came on. fuel filter just chaged, plugs last year. I've had COP's go bad, that's what i thought but this is different.

 

What BRAND of plugs did you use? If they weren't Motorcraft, CHANGE them.

 

I believe they were Autolite. If i change them to Motorcraft, which one should i use?? Only ones i can find locally are Motorcraft Platinum Iridium. Are they good, bad, what should be there or overkill?

 

Stock plugs are SP493's.

 

Oh wow I didn't know that uneek had DG511's out. Thx for the heads up.

Sorry for the threadjack, but that saves me a ton of money.