My 1998 F-150 5.4 with 120,000, 2wd, auto. I am having a problem with it running rough when first driving it for the first 5-10 miles, after that is seems ok. It seems like its missing, trying to maintain 30-40 miles an hour if jumps and sputters, acts like its missing a plug or something. Its been doing this for over a month but no cel. I have been hoping one will come on but no luck. The cel does work when ignition switch is turned on, so I know its not burned out. Any ideas? I put new cops from Summit on about 10 k miles ago with new plugs and it ran really good after and gas mileage went up too, but now this. I have sprayed the throttle body, wondering if it needs to be reomved and cleaned, but then no code???? I'm just a parts changer to save money, I know it takes a real mechanic to diagnose.
Any ideas would be appreciated.
Thanks,
Dave

 

check the fuel filter.

 

Just to clarify, engine misfire is when trying to maintain a speed of 30-40 mph. When accelerating, truck does good. Then everything seems to be good after truck warms up 5-10 miles. No check engine light, can't find a vaccum leak, seems like maybe something heats up then it runs ok.
Thanks,
Dave

 

My 2002 with 4.6 was doing the same thing for months then it started to show a CEL of #2 misfire.. I installed a new COP on #2 and running better than ever now.. So maybe you should just wait till the light comes on to let you know which cyl. is misfireing....

 

i think i am having a similar issue have you foud a resolve.

 

No fix yet, I want to try the fuel filter. Does yours run ok after 10-15 minutes?
Fleet mechanic at works thinks it could be a cracked intake manifold or intake manifold gasket

 

how would a cracked cold intake manifold let in air but not a warm one?

i would bet the money on the ignition

 

He said it could expand when hot, sealing a minor leak I guess.

 

Hey. I replaced the fuel filter tonight, had alot of brownish colored fuel run out of the inlet side of the filter when I removed it. Engine is running much better, not sure if its completely better now, need a few cold start trips to evaluate it, but it is definately ALOT better.
Thanks to all from sunny, WARM, MIAMI! LOL
Prayers go out to all who are without power from the ice storms.
Dave

 

Still mis-firing wtf lol.
About to surrender and take it to dealer.

 

how about you stop driving your truck until you have it checked for codes (there can be a code without the CEL), maybe you have contaminated gas?



if you have no codes I'd flush the tank and change the fuel filter again, change the cops and plugs and see what it's doing then

 

Thanks tara!
How do I find a code without a cel? Do I need the dealer to scan it? Usually I go to Autozone or the like and use their scanner. I have ran seafoam through the tank, then changed the filter. How do you suggest I flush the tank? Do I need to remove it?
Thanks.
Dave

 

So, I took it to the garage, they couldn't find any codes or indications of anything being wrong. $82 down the tubes lol. I am thinking now I will start examining the plugs, see if one is cracked. Whee.... I CAN'T WAIT TO START REMOVING ALL THAT CRAP to access the plugs!

 

So, the mechanic who did the analysis ($82) )thought it acted like a cracked plug. I just got done removing and checking each plug and they all looked good. My BACK isn't feeling too good now, but I think I can eliminate the plugs being the culprit. No idea what to do now.
Dave

 

OK update mine is still doing it sometimes... Mine starts and runs just fine till it's just about up to operating temp. then it starts missing for a couple of seconds but only if I'm getting on the expressway and trying to get up to speed. It seems to be while going from 45 to 60 then it smooths out and runs fine for days. Haven't notice it just driving around town.. I'm thinking that the computer is going lean to quickly or I have a plugged injector... I'll try some cleaner and see what happens... Bob