Hey Guys,

In trying to diagnose my own misfire or hesitation issues I've been doing quite a bit of searching on this website and the problems I'm having seem to be fairly common. That said, however, the answers sort of span several systems. I've changed plugs (Motorcraft OEM), COPS (Global) and plan on changing the fuel filter tomorrow but don't expect that to change much. When I first crank the truck the sputtering starts as soon as I put the truck in gear but then smooths out until under load (climbing a hill, accelerating, etc). Once under load it really begins to act up but once at speed it smooths out. I've checked and rechecked the cops/plugs and all seem good. Based on my search I'm thinking it could be the fuel filter, EGR Valve or MAF Sensor. Before I go changing parts (low on money right now) is there a process of elimination one can go through?

JBrew...you always seem to have some good insight so I'm all eyes and ears

 

I'm not Jbrew but I'll throw a few things out there...

How many miles? Get the fuel filter changed. If you say it starts as soon as you put it in gear, have someone put it in gear and keep the brake pressed while you get under the hood and individually unplug each cop one at a time at the electric connector. Look for one that doesn't change the way it is idling. Same thing with your injectors. Just because the cop's are fairly knew doesn't mean you can rule them out. Try cleaning your MAF sensor also.

 

A misfire under all loads and no CEL ?? No, that's not common at all. In fact I can't recall anyone having this problem in the past.

Definitely sounds like a fuel problem. Your losing it under power across the board (so to speak.)

You should have a CEL/ A blinking CEL if anything and a DTC for multiple misfires.

Fuel filter is my guess as well.

 

Found part of the problem for sure. Finally threw a code this morning (these things are stuborn about codes) and again it was the #4 cylinder. Pulled the cop again and retested it. It looked good on bench test but then I replaced it with an old cop which cured the misfire. Still have some hesitation which leads me to believe it's the fuel filter. I'm starting to feel like I'm chasing my tail.

 

So you had a bad one from Global ? I'm keeping track lol. Yea, you should not have even the slightest hesitation. These engines generally run real strong when maintenanced properly. There's no signs of coolant leaking above 3 and 4? If you rested the comp/ relearn mode, that little hesitation will get worse in the next 20 miles or so. You'll notice this, specially if it's another coil. So these coils are new, out of the box ?

 

Depending on the mileage and how low you've run the fuel in the tank over the years, the fuel pump could be letting out. Its probably having trouble maintaining pressure when your engine requires it under a load but can push hard enough to run the vehicle under its own weight. I had one replaced in my 99 F150 before I sold her off, it was at 123k miles. It would run fine for the most part under light accel but if I got into it, she started bucking and around 55 to 60mph you could tell it was having trouble.

 

It appears a bad one slipped in . There is no sign of coolant leaking anywhere. I'm not sure what you mean by "rested the comp/relearn mode" so you'll need to splain Lucy.

I've been running it this afternoon and no futher misfires but a very slight hesitation when I jumped on the gas. It really feels like it's not getting the fuel it needs. The fuel filter needs to be changed and I will get that done this week so I'm hoping that will solve the problem. Anything more and I might have to get my SAE certification LOL...

 

Clean the MAF for good measure also. Was very noticeable difference when I pulled my TB and completely cleaned everything from egr ports to IAC and MAF. Truck was a champ after that. I now see those things as standard maintenance. Even though some may think its over the top, but I plan to do that at least once a year.

 

Now reading this, I feel I've been having a similar issue around 50mph. I notice some hesitation going up a hill & I have to give it some extra gas to keep going.

 

It's not just the speed, - If it's a coil, the misfire load hot spot is right after the shift into OD. That's when a bad coil will be at it's worst.

 

Yep, my #5 cylinder is misfiring again. Replaced the plug and COP, still the error code shows up. I'm going to replace the COP again since the spark plug is new. Hopefully that issue will go away.

 

Happened with several POS Acell COPs. Wound up sticking the stackers back in.

 

Finally replaced the fuel filter today and no more hesitation. Truck's running great. It's amazing how big a difference such a small part can make. Now to fix the occassional shudder and we'll be back to normal.

 

Might be time to clean the MAF sensor

 

Run some fuel injector cleaner thru the system to. I use Amsoil's stuff. A bottle will treat up to 25 gallons i believe.