Just as the title says, I'm experiencing a slight miss at idle. It's not enough to through a code or to track down which cylinder by switching coils or such. It's just very slight. I changed plugs around 50k miles, truck now has 66k miles and seems to run perfectly fine otherwise. I Hate to go spend a bunch of money on coils or 02 senors or redo the plugs or what have you without having some idea what the cause is. Any ideas on how to track down this slight miss. I do have a few broken exhaust manifold studs but haven't noticed any leaks yet. otherwise truck is in ship shape and has been well maintained.

 

Did you actually check for codes or are you assuming that because you don't have the MIL lit that you don't have any codes?

https://www.ford-trucks.com/forums/5...t-come-on.html

 

Replace the boots that's what I did and my miss at isle went away.

Denny

 

Check out this link https://www.ford-trucks.com/forums/1...000-miles.html

I had a plug go bad after 4,000 miles. I tried for days to identify the problem finally took it to Ford, it was only like $75 bucks to diagnose.

 

I say run a can of SeaFoam through the fuel system. Start with the easiest things first, rule #1 of troubleshooting.

 

First thing I'd usually rule out first is bad fuel with adding some water remover. The temp swings you see this time of year can cause condensation in a tank already filled with questionable fuel. The ethanol mixes with any of the water and it settles to the bottom of the tank.

 

I doubt it's fuel as this isn't a new developement, it's been doing this for probably the past year over several tanks of fuel. It's very minimal and not a continuous miss. DKF, although the truck does sit quite abit now that I have a new work truck (3.5 Ecoboost F150 Lariat), it is sitting in my heat controled garage which is set at about 60 degrees.

I'm actually kind of on board with RV Puller on the boots as I could check the plugs at that time. When I did change the plugs, I didn't change the boots so it wouldn't overly suprise me if that was the cause. my inistial thought is ignition; plugs, coils, or boots however is there any chance an 02 sensor or something else might be causing it. I suupose a weak fuel injector however that seems fairly unlikely as they seem to either work or not.

 

A relative of mine has been having an intermitant issue for the past 8-10 months which they thought was chatter from the transmission because it started after a fluid change. Turned out to be a misfire caused by water in the gas tank. The vehicle is kept in a heated and air conditioned garage driven about 3k-4k miles per year. Food for thought.

If the boots are old it won't hurt to change them though.

 

First things first, just pull the COPs and check for moisture. No matter what I do, new boots, dielectric grease around the top of the boot, whatever, some water gets down at least one hole sooner or later.