I took my truck to Chicago this evening on a business trip. It started missing when a light load was applied (like going uphill) seemed fine when I put my foot in it. About 70 miles outside of Chicago, it got reallllly bad. I put my foot down, the missing continued then when I let off, the CEL came on and flashed for about a minute. It seemed ok, so I floored it again..CEL flashes, then goes out. I don't have my code reader in the truck.

I slowed down to about 65 and while the missing is still there under load, it seemed happier. Acceleration from a stop seems ok until you get to about 55, then the miss becomes detectable again. After I got to my hotel, I gave it a few no load revs and there is a detectable stutter at throttle opening that disappears.

Few things come to mind as suspects. COP cracked? Dirty MAF?

I'm just hoping it gets me home tomorrow after I get this testing done...

 

I made it home. The truck was acting up all the way out of Chicago, almost to West Lafayette. The sun went down and the air got cooler, the truck starting behaving. By the time I got home, air temp was in the 50s and the truck seemed near normal.

I ran the codes and got no codes at all which is puzzling becuase the CEL was flashing. Should have left something behind...

I'm thinking I have a Coil going bad. Anyone have any method for checking them that is sure fire?

 

use a spray bottle and hit each one while it is running, most of the time they crack and the water will get inside and you will know when you spray the right one! also it should set a code in "history", your code reader may only read "current" codes so get it read somewhere and then switch the coil on the cylinder that flagged the miss with one of the others, when the light returns if the misfire moved with the coil it needs a coil, if its still the same cylinder then it will need to be diagnosed further

 

The issue persists. Still no codes, active or otherwise. I found a vacuum hose that runs from the Throttle to some sort of regulator on the fire wall (other connections go to EGR and Fuel tank) that the outer coating was converting to carbon in my hands. Ah Hah, I thought. Replaced it today and still have the issue.

The miss seems to be air temp sensitive since it is less invasive today (50 degrees) than it was Wednesday night (70 + degrees).

My thoughts at the moment are either a weak coil (not broken down enough to toss a code yet) or a vacuum leak.

Anyone have any insight on this?

 

HAVE SOMEONE BRAKE TORQUE THE ENGINE IN DRIVE, (WITHOUT SPINNING THE TIRES) AND IF IT MISFIRES UNDER LOAD YOU CAN START UNPLUGGING COILS ONE AT A TIME (UN PLUG THEN PLUG BACK IN) UNTIL YOU FIND THE ONE WHERE THERE IS LITTLE TO NO CHANGE AND THAT IS YOUR CYLINDER THAT IS MISFIRING, THEN SWAP COILS (CAUSE IT EASY) AND DO IT OVER AGAIN AND SEE IF IT MOVED WITH THE COIL OR NOT. YOU COULD ALSO PULL PLUGS AND SEE WHAT CONDITION THEY ARE IN AND IF ONE OF THEM LOOKS FOULED WITH FUEL. IF YOU HAVE NOT DONE A TUNE UP IN A WHILE JUST REPLACE THE PLUGS ANYWAY! GOOD LUCK

 

This is a sad story. Replaced ALL coils with APX coils from eBay. Replaced plugs since I was there. One note to all of you thinking of replacing plugs, it aint as easy as some on this forum would lead you to believe. It was a 9 hour evolution (although to be fair, it was interupted by a power outage).

The truck ran fine for about four miles and then the mystery miss came back. I kept trying to get the miss to occur (successfully I might add). After 6 miles the flashing CEL was on and my rider was able to pull Misfire 1 from my reader. The truck was barely driveable after 8 miles. I took it to my local Ford dealer (whom I trust with the Queen's Mustang implicitly). They put it on the computer, and pulled misfire 1 and 5. Swapped out plugs and coils between 1 and 2 and 5 and 7. no more misfire 5, but 1 persisted. They borescoped cylinder 1 and the exhaust valve is toast, leaking oil on the cylinder and fouling the plug.

I am now looking at $2500 for a reman 5.4 and around 2K in labor at Hidy.

Lesson - Before you buy a truck that seems to good to be true (63K miles, perfect body and interior for 5K) spend a hundred or so to have it to have it diagnosed and inspected.

 

Can you just rebuild the heads? Seems to be an easy and cheaper fix. I would think you could do the labor yourself outside of the head rebuild unless you have the skills.

 

If this were any of my old F100s or F150s, I'd already have the damn thing apart.

The engine bay on this thing is too tight to really get it apart without dropping the engine. And I don't have the space or equipment (or time) to do that.

 

That sucks man, but at least if you put a new engine in there it will be like a brand new truck What I would do is pay for the brand new engine, and have someone else take out your old one and put the new one in...2K is too much!!!

 

I'm taking the middle ground on this. I was refered to a local shop by my uncle. This guy was going to do the faulty head for 2K (labor, parts and machining). I asked him to compression check the other bank as well (5 through 8) and he found 2 cylinders there at 90 PSI.

Sooooo.... Now we have a line on a 32K mile engine that will be here Friday (has a 1 year warranty, didn't know you could get a warranty on a used engine) and is costing me 3K, parts and labor. Should be done next week.

Moral of story, ALWAYS pay for an independent assessment when buying a used vehicle. Sure, I would have lost a hundred or so bucks, but I wouldn't have bought this incident waiting to happen that added 3K to the purchase price...