My 2006 f150 developed a slight miss that got worse. seemed mostly at acceleration. One auto store found no codes, another said it was no 8 and i needed to replace coil. I replaced coil, no change. Went back he said spark plug, could not get loose and didnt want to break so went to Ford dealer. They 'diagnosed'? it was not plug but may be timing chain and possible $2200 job. is it normal that a timing chain go out at 60,000?
could this be a vacuum leak? it was running pretty rough to go to dealer, not possible to keep driving that way. comments please

 

You said one autoparts store found codes and the other didn't. Was the service engine light actually on? It's hard to tell what is going on without some scan data.

 

the light was not on the first time. on the way to other store i floored it and it came on.

 

What was the code?

 

the auto part goy did not tell me. he said it is misfire on #8.

 

Are you 100% you changed number 8... not trying to say anything bad just make sure it was 8.. If you changed coil did you also replace the boot usually comes with it, the spring in coil boot is sometimes the colprit... had same problem in my old truck, once they start you might as well replace them all if possible....

Think these are the ones i bought not 100% sure tho its been awhile...
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There's only one way to really rule it out...change the plug.

I had a really bad misfire that got progressively worse over the course of 8 months. Finally a few weeks ago, I started getting a flashing engine light. The manual says that the check engine light flashes when a miss is detected (that's kinda nifty). So I scanned for DTC's with my Edge and it came up as a miss in cylinder #7. I did all of my plugs last weekend, and it solved the problem.

You may want to break down and change the plug. A little bit of time could save you a ton of money.

 

I would find you a new dealer to goto.. The timing chain thing is a load of crap, your engine would barely run if at all and it would not have been a gradual problem that got worse over time. Your problem is more likely a COP or spark plug issue.

 

Sounds like I had a similar issue as well. Started out with truck not starting correctly, every once in awhile had to give an extra crank to fire. Took it to parts store and garage, computer stated cylinder misfire but couldn't tell me which one. They suggested that while the motor was running to pull the harness off of each coil pack one at a time. If the plug was fine, the motor would kinda bog down. I pulled until I found the one and replaced it. No change. Turned around and did the whole process again, and found one that appeared to be fine previously, now seemed to be bad. I gave up, as I figured I was pressing my luck in busting one off. Drove it for a few weeks, then she started to cut out or miss a little, then it became alot worse. Ended up ordering a puller tool online for plugs that may break, $40 i think, and took a Saturday to change them all out.

Local shop told me 4-6hrs book time, i think. And then $150 for each one that breaks. NOT this cowboys pocket, so I tackled it myself. I wasnt as lucky as most. As careful as I thought I was, I broke three of them. The one up against the firewall was the worse, but with a few choice words and few beer breaks that little puller tool worked.

I of course spent the little extra on one peice plugs to go back in, what a stupid idea Ford used there.

Good Luck

 

I had a simialar thing happen with my 06 fx4, cel light came on, I scanned it, replaced the spark plug and the coil, cleared the code and a week later it cel light was back on. so I cleared the code a couple more times aand started running sea foam through the fuel tank and switched fuel vendors and problems faded away. I think that injectors were getting dirty and leaking into cylinder key off and flooding that cylinder on start up, hope this helps!

 

UPDATE ON PROBLEM; I declined the timing chain job at dealer, so they wanted to keep another couple days for more checking. Next phone call was YOU NEED a MOTOR $7000 approx. Reason; missed oil change , motor sludged. Went to dealer to look, did not see sludge (down removed oil fill tube) but oil was old. Mechanic says maybe flush may fix, no guaranty.
Sales manager stays with 'new motor". I say no to motor, then USED MOTOR? save you some money $5000. I say no, ok how about flush for $100. I asked several times to explain dirty oil causing miss.Here is the answer;
Oil gallies are very small that are supplied by a selenoid that is controlled by computer. The gallies supply oil flow to lifters.
When I got the truck back it had turned to almost $300 bill. Runs the same as always did. No miss.
Does anyone know if this is true about the small gallies and could this be right or were they trying to sell an engine and perhaps it was one plug they changed anyway without telling me to fix problem.
It does seem the sales manager was testing to see what I would buy.
Also the oil pressure never moved from high mid scale where it started as new and temp never changed.
Anyone who knows how oil system works in 2006 5.4 info appreciated.

 

are you using synthetic?if so I can't see sludge forming.how often do you change oil and filter?make sure you use a good filter like a NAPA gold,stay away from fram.
the passages on alot of newer motors seem to be narrow so the oil dosen't flow fast and over time the oil cooks from engine heat causing sludge. Thats how it was explained to me after my dodge had a sludge problem with 55,000 on it

 

Just an update. the miss was tracked to coils. I am still driving just fine except for occasional miss on acceleration that I know is coil. When I can afford I will change them all. Driving down the interstate still runs like a new truck. Codes were cleared and haven't come back.