My 4.2 sometimes had very slight rough idleness and a more pronounced one occasionally when I came to a stop after driving highway speeds for some time. A few weeks ago I started getting a constant brake and ABS warning lights. When I took it in a few days ago for the brake warning light fix, they replaced the brake computer module and the brake 'electro hydraulic proportioning valve' and RABS valve. Now I don't know what all of that is except I do know (I think) that the RABS has to do with the vacuum system. Anyway, as it turned out, I no longer have the rough idle. My service guy said it must have been a vacuum problem that was connected to the brake vacuum problem.
Does this make sense?

 

Just about to roll over 57k and no rough idle. Once in a while I get an occasional miss, but I figure that to be caused by a tank of poor quality gas.

I was originally thinking the cause of the rough idle for some of you may be due to bad coil packs, but looking back through some of the posts there are a few 97 and 98 owners also reporting rough idle. I don't think they started using the coil packs on the 4.6 until 99. Guess that theory doesn't hold water huh.

It amazes me how these trucks are built to the same specs and tolerences and one has the problem and the other doesn't. One truck gets 18mpg and the other gets 13.

One owner can baby the truck and it will be in the shop all the time, another owner can beat the crap out of the truck and drive it trouble free till the wheels fall off. Go figure.

 

I'm back and yes my rough idle is still around. Haven't had much computer time lately. I have had one DSB hearing and about to have a second on my rough idling 5.4. I will keep everyone informed on what happens. Thanks for the support, information and friendship everyone has given.

Please add your name to this site if you have the rough idling engines. DonW has done something excellent and I personally thank him.

http://home.pacbell.net/donw35/f150[URL]

 

KEEP THE RESPONSES COMING EVERYONE. FORD DENIED ME A REFUND OR REPLACEMENT OF MY TRUCK SO I WILL HAVE TO TALK TO MY LAWYER ABOUT A LEMON SUIT. THANKS

 

OK guys. My now dead 97 had the rough idle problem. Took awhile but I finally fixed it. The 5.4 is very prone to plug gap. When I pulled my plugs they were all over the place (way to go quality control). I replaced the plugs with copper plugs and gapped them at 45 on the dot. The truck ran fine till the aerostar killed it. I now have a 2001 SCREW with about 4000 miles on her and no piston slap or idle issues (knock on wood) so far. I am about to change the plugs and put the blower on her and see how she go's from there.

 

About 84K and no rough idle, yet.

 

Hi everyone just registered. I have been only reading until now, but i had some info on this issue. I have a 2001 F150 4.6 when purchased @ 12,000 miles had a rough idle w/ light on. Brought to dealer , they replaced mass air flow sensor. That worked fine for about 1,000 miles then no light but lots of hesitation and rough idle. Returned to the dealer and told of same problem occuring and no top-end. They called me 3 hrs later said I could pick it up in an hour. He said it needed a THROTTLE ASSEMBLY and reburned my chip. They also stated they " had a run on these lately " . That was 5,000 miles ago and I have increased torque and no prob's. Hope this helps everyone.

 

97 F-250 LD 5.4l 4x4 SuperCab, no idling problems, no piston slap!

 

Thanks everyone keep them coming.

 

I don't have a rough idle per se, inasmuch as my 36K mile 5.4's tach stays put when idling, but I do have a vibration through my brake pedal that is very annoying. I took it to the dealership for repair. They claimed to find the problem and proceeded to replace a broken exhaust hanger...WRONG, problem still exists. It is most pronounced when the A/C compressor kicks on.

 

Ya , mine to! It doesn't always do it however. I have a 99 5.4l with 32,000 and it started doing it just recently. Occasionally, when I start it up in the morning it really idles rough, but seems to go away after the Engine warms up. Than again, on some mornings it start up and purrs like a kitten! I'm not sure what to think. I'm taking it in to the dealer for a list of things like the door crack, leaky rear window and flaws in the paint before the warrantee runs out. The rough Idle will also be added to this S__T list!

 

THANKS EVERYONE. PLEASE KEEP THEM COMING. PLEASE

 

MORE RESPONSES NEEDED PLEASE.

 

EVERYONE PLEASE CHECK OUT THIS SITE AND GET YOURSELF ADDED TO THE LIST OF ROUGH IDLING F150'S.

home.pacbell.net/donw35/f150

 

At 42,300 miles my check engine light came on. Took to my service guy (not a ford dealer) and a O2 sensor went bad. It was the one passenger side before the cat. so far, the rought idle has gotten better, not as good as my 2001 Expedition but better none the less.

If you have this problem check out the F150 Rough Idle website and get added to the list.

F150 Rough Idle page