2008 F250 5.4 L

dpendzic

Well-known Member
My trailer tow vehicle develops an intermittent miss. Been to the Ford dealer 3 times, first two couldn't find anything, but on third visit found a misfire on a couple of cylinders. They say it might be the spark plugs, but at over $500 to change them I am hesitant to gamble. Is there any way to determine if it is the coil pac on a cylinder? There is 76,000 miles on the truck
 
Those 5.4's were kind of notorious for stripping the threads and blowing the spark plugs out of the heads.I think you will find the reason for the high price is most guys just count on replacing the coils when changing the plugs in those things.If nothing more,the plugs should be replaced just to verify they are staying tight.I replaced a set on a truck with about 80,000 on it,three out of eight were loose.It was running fine,but the owner had heard horror stories about the plugs getting loose and blowing out.
 
The plug stripping issue was long solved by that time. I would say you need a better dealer as they should be able to tell if it's a coil or plug issue. At that many miles your due for plugs tho.
 
I have owned 5.4 and 6.8 Fords since they made them. 5.4 Spark plug thread stripping was "fixed" long before 2008 by a redesign that allowed the bottom of the plug to twist off and stay in the head when you attempt to remove them, I think 2003 or 4? . The twist off plugs were eliminated by 2008 so you should be fine in that respect.

As for your missing intermittent problems like that are the hardest to diagnose and will cost you some money no matter how a dealer goes about it. Since service hours spent on diagnoses and trips to the dealer add up to $$ just like hard parts most dealers will want to change the plugs to eliminate that variable at the get go, not to rip you off but it is the quickest easiest route to figuring it out. After that if the missing continues A scan tool will say exactly which cylinder(s) it is and they replace the coil pack. The alternative to that procedure requires identifying which cylinder(s) are missing, then switching coil packs from those cylinders to others that are not missing and wait and see if the problem moves with the coil pack or stays at the same cylinder. If the miss stays at same cylinder they change plugs, if it moves they change coil packs,might save you a few parts but all the time in the shop adds up too. Good news is seldom is the problem elsewhere like wiring or ECM. We do this ourselves as we have the tools required to do it.
 

As Butch mentions, get you an OBDII scan tool.
The port for it is likely under the dash near the steering column.
I got an Innova 3040e scanner from amazon, currently $77.

We have a 2008 Chrysler Town & Country van and the check engine light comes on ALL the time for silly stupid stuff.

If I took it to the dealer for every CEL it would be in the repair shop more than in our driveway.

The scanner tells you why the CEL is on and lets you reset the CEL.
 
My son had that issue a few years ago on his truck. Plug wires were to blame. Had an independent shop replace them with aftermarket. Lasted a few months. Ford dealership replaced with factory wires. No more problems. Original wires heavier than aftermarket. Cost a bit more but lasts enough longer to be less costly in the long run.
 
As mentioned, a scan tool should pin point which cylinders are misfiring.
Sometimes it's not the plug or coil that's at fault. The rubber insulating boot on the coils get pin holes in them.
I had that problem on a 2000 F250 with 5.4. I replaced the boots for a fraction of what new coils cost and fixed the problem.
 
I bought a set of coil pacs off EBAY for less than 50 dollars. Easy to change and still working several years later when truck was sold.
 
It is time to change the plugs. But should not be a problem in a 2008. A few years back my 2003 5.4 towing a tractor about 300 miles from home started missing bad. Found a good private garage. The guy had a Ford scan tool. Told him what plug was missing. But it was the coil pack on that plug. He said. You have been washing your motor. Blew water into plug boot. 3000 psi will blow water past seals. Needless to say I haven't washed my motor since. No trouble either.
 
Guy at work had a 2007. Had a similar problem. His looked like someone attempted to put a repair sleeve in one of the plug holes and it cracked or something ? or cracked the head ? He could not get rid of that mis. Instead of fighting it any longer he traded it off on a nice Toyota !
 
well i drove the truck over 200 miles to get home. It misfired a bit but by getting the rpm's up to 2000 it ran fairly smooth--i also stopped and poured more Lucas injector cleaner in it. Hooked up mt OBD2 and it had no codes stored. Watched 6 youtube video's on the plug replacement--loos like its important to prep the engine and plugs before attempting removal of them
 
That is not uncommon, I drove my current truck, a 2010 6.8 home from Pa with two dead cylinders and it never lit the CEL nor did it set a code. An intermittent miss may light it immediately but a completely dead cylinder may take a very long time light it. I had to locate the missing cylinders by feeling the exhaust manifolds after a cold start. There should be no issues with plug removal on an 08. It helps to get the 9/16 socket with the built extension that is made for the job. OTC I think? However there is a slight issue with installing the new ones as they break VERY easily. You must hold the head of the ratchet with your other hand as you tighten them and listen as you tighten the plug, if you hear "clink" you might as well take it right bac kout. I learned real quickat $10 per each plug.
 
Our 2008 Chrysler has the 4.0 V6 with coils on plugs.
It would turn CEL on and the code reader would say #5 cyl misfire.
Could not feel it nor hear it so I figure it was a one or two times in a row misfire.
Then one day it was very obvious that one cylinder was not firing at all. Very pronounced when down 17% of cylinders.
CEL code again said #5 misfire.
Pulled upper plenum off and rearranged the coils. Put back together and started her up.
Obvious miss still there and code reader said #6 misfire which was formerly on #5.
Replaced that coil with new one.

I know the coils send a "confirmed fire" signal to the computer and when a coil fails to do that the CEL comes on.
If a plug fails to fire, I do not think there is any such confirmation signal as there is no connector, etc. it is just really a fancier version of a 100 year old device.
So when a plug goes bad your not going to get a CEL.
 
They're quoting that big price to cover time to extract any that happen to break off. The Lisle extractor tool works very well. The secret to getting the plugs out in one piece is use a 3/8 impact. Once I started doing that I seldom broke any off in the head.
The reason Butch's truck didn't set a code is being a 250 or bigger back then the emissions were not as stringent on 3/4 ton and larger so a code may not even set. In order to find the misfire(s) you need a scan tool that can do cylinder contribution on a Ford. Most inexpensive units don't have that ability. If it were in my bay, and I verified it was ignition (usually is), I'd replace any coils with a misfire and all 8 plugs. When you put the new plugs in, coat the tips, NOT the threads, with antiseize and the next time they will come right out. There's a TSB from Ford for this.
 
thanks--got a second price from a local Ford dealer--$660 and $140 more per plug if it breaks. I read about antisieze--I assume it has to be high temp--most are good for 1800 degrees but there is one good for 2400 degrees, i think its a nickel base compound. Need to get more quotes from local shops and not ford dealers.
 
My son got so tired of replacing coil packs on his, he started buying them at a salvage lot. When the darn thing started missing, he would pull into an O'Reillys, get a reading, pull a coiol pack out ta the glove box and go on. The boys at the car dealership I worked for kept a dozen on the shelf.
 
The trick to getting the plugs out without breaking them is to do it with the engine hot and after you do one bank of plugs restart and reheat the engine before doing the second bank.
 
well had the plugs changed and did all the pre removal advise--every single plug broke off but my mechanic had the removal tool and they all came out. Just drove it 200 miles upstate and it ran good
 
Misires are figured by crankshaft
accelerations between crank position sensor
pulses. Coils have nothing to do with
reporting misfires.
 

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