With mild acceleration the engine seems to "miss". When going up a mild climb on the road at say 50 mph or when getting onto the freeway it is more noted.

To get the truck going (because it is seems to 'miss') I accelerate harder and RPMs seem to dance a little while speed increases. For example, when accelerating and it starts to 'miss' I click it off OD until I get to the desired speed. Once at desired speed it can still 'miss' from time to time but it is most noted when when accelerating.

I changed my fuel filter a few weeks ago and it did not make a difference. What does help is putting in caburator cleaner with every tank. I am not sure why that is required. Higher octane does not help...but he cleaner seems to.

It idles okay (maybe a little rough). If I take it into a dealership or shop do I need to have the mechanic ride with me so I can reproduce the symptom? How can I figure out what is wrong? Can this be diagnosed with hooking it up to a computer? To me it sounds like the timing...can the timing be off? The check engine light is not on.

Thank you for the replies.

 

I have the same issue with my 1997 5.4
I just got this truck and I thought is was the transmission because it got better when I switched off the OD. well, today I noticed that all I was doing was changing the engine speed which helps the miss to go away.

So, I too am perplexed. I've read in other posts that it could be a COP, whatever that is. Also could be a sparkplug and wire, a fuel filter or IAC valve. I did find out that and IAC valve is a motorized valve for the air intake which controls the amount of air the engine is allowed to suck in.

Occasionally after freeway driving my check engine light will come on for a while.
It goes off again after a while or if I turn off the engine and start it again.

This miss is not regular, it is annoyingly non-rythmic. The miss only occurs after the engine and tranny have warmed up and only under a slight load. Also, the engine will miss at idle. The miss mostly is felt at all speeds up to 55mph for me but it is worse at 45. Also is definitely clears up at 65+.

Bill

 

I used to be a tech at a dealer and used to see that quite often.

80% of the time it was a bad COP boot.
It would allow spark to arch against the cylinder head.
Yes,hooking it up to the tested at the dealer will reveal which cylinder it is.
Otherwise,you will have to remove all COPs and closely inspect the boots.
If you see a white spot that stands out in the black boot.then you will have found your problem.

BTW,power brake the truck,and you will see that the miss will be duplicated.
When the boots arch,the miss usually only happends when under a load.
Hope this helps.

 

Thanks Baja FX4.

Does anyone know what a COP boot is and what do you think is a reasonable repair cost? Does the whole "boot" need replaced?

 

Rather than having plug wires like most vehicles, these F-150s have COPs, which are coil on/over plugs(I believe). My truck was recently missing badly under acceleration as well because of a bad coil on the seventh cylinder. It costed about $130 to have a new one put on.

 

I have replaced two COP's. Easy job, and costs less than $40 to do it yourself. Search the F150 forum for "how to change spark plugs" or "COP" for a plethora of information.

 

I had the same problem but the Check Engine light would never stay on so I could read it with a normal code reader. I ended up getting the free software and bought an OBD2 cable from http://obddiagnostics.com/ and drove around with it hooked up to my laptop. I was then able to find out what COP was bad.