Ford 5.4 engine miss

[Ryan03]

It could be many many things. In my professional opinion, you must first isolate whether you are battling an intermittent spark problem, or an intermittent fuel problem, then proceed accordingly with narrowing it down. I have duct taped fuel pressure gauges to the windsheild and driven for hours more times than I can count over the years to catch a fuel pump going south or a regulator hanging up. I have used a hair dryers to heat electrical components on dead cold engines such as coils, TPS's pickup coils, modules, etc. to duplicate heat related problems. Check the MAF sensor readings on the data stream as well, idealy when the engine is falling on its face to verify proper function of the MAF. If the truck uses a oiled gauze air filter such as a K&N, this is the first place I would look.

More info on the miss would be helpful, does the engine flatten out and cough like a carbed truck with a malfunctioning choke, or is it a steady miss, like a plug wire has been removed.

 

[ModMech]

There are many things that can cause intermittant misfire symptoms, but from late '99 thru '02 Ford had a real problem (I'll call it) with COP durability. I know a few ppl that just go to junk yards and buy a set of later ones for $50 and change them all just to avoid a problem. I also know folks who have had all 8 changed during the warranty period, one at a time. Now that's maddening!

Sure, fuel pressure, injector spray patterns and MAF sensor fouling could also be contributory causes but THE most common root cause is a bad COP or two.

 

[Pops15]

I haven't had time to look into it yet but I'll address some things mentioned.

I'm going to guess I have one of the non-compliant SD's and that's why I'm not getting any reading.

Not sure where the fuel filter is on a F150. My fuel filter is inside the frame under the driver seat.

Since the worst problem is under acceleration, and it clears up some when I back off the throttle, I'd say it acts like a carbed engine with choke problems or a carbed engine that's over carbed.....or the computer causing the timing to be off. But occasionally (maybe even rarely) it will have a miss at idle and low rpm that acts like a dead cylinder.

I cleaned the MAF sensor and it made no difference in performance.

My driving is about an even mix of highway and city. Rarely more than 15 miles per trip.

Has anyone had computer problems? What were the symptoms?

I'll probably have time late in the week to look into some of your ideas.
Thanks for the help!
Pops

 

[crashz]

Kebo,

Same location as Pops mentioned for the F150. I was changing mine (2001 F150) at a rate of once per every 10,000 miles and everytime I would drain the inlet side and see nasty rust, dirt and gunk. Bad gas I think, because the truck was not very old. I traded it in when it was only 4 years old.


Pops,

My current GMC blows lighter and accessory fuses quite regularly. One or the other is tied to the OBDII port power and I had the exact same symptom as your are seeing with your scanner. My CEL came on eventually, and replaced the correct fuse and all was well again. The CEL must have been tripped due to lack of power to the OBDII port.

If your computer was malfunctioning or even not compatible, the scanner should at least power up. Sounds like you need to tackle that first. My Ford had a coil pack (mine was a V6) go bad and it went from a slight irregular miss, to a dead cylinder to activate the CEL. The coil pack was a bit different, but did have a big crack in the bottom at 100K miles.

Best of luck!

 

[slowzuki]

Little late to the game, I had the same problem with my 5.4 in my SD. Found 2 bad cop's, one torn boot, and one wet (as in water) plug well that ruined a boot.

This is the best guide I've found for diagnosing:
Part 1 - Testing the FORD Coil-on-Plug (COP) Coils

 

[kebo]

Has new EGR valve. Found a bad boot on one coil. I replaced all of the boots on the coils. Also replaced one coil. At $40+ each I don't want to replace the other 7 coils if don't have to. How common is it for a COP to have an intermittent problem?

I get a blank screen with the scanner. No reading whatsoever. Makes me wonder if its a computer problem.

It's not that uncommon for COP's to go bad or intermittent, I have one on mine that I think is intermittent now. I've already replaced 4 of them over the 8 years I've owned it. Not certain that the COP is the problem, but the other day the check engine like came on and I had the code read off of the computer and it indicated a misfire, but it couldn't identify which cylinder it was coming from. They reset the light so I'm just driving it and hopefully one day soon it will go bad enough to register enough misfires that it can tell me which cylinder is causing it.

 

[Diamondpilot]

It's not that uncommon for COP's to go bad or intermittent, I have one on mine that I think is intermittent now. I've already replaced 4 of them over the 8 years I've owned it. Not certain that the COP is the problem, but the other day the check engine like came on and I had the code read off of the computer and it indicated a misfire, but it couldn't identify which cylinder it was coming from. They reset the light so I'm just driving it and hopefully one day soon it will go bad enough to register enough misfires that it can tell me which cylinder is causing it.

If it did not pin point a cylinder number and was just a miss fire its probably not a COP. Last Lincoln I worked on I found 2 vacuum leaks that were the cause. Also check the hose going from the PCV valve to the Intake Manifold. My code scanner led me too it. It not only tells you what is wrong but common problem areas to look at.

Chris