Engine missing and running rough under hard accel.
 

Hello,

My 99 150 4.6 started missing and running rough under heavy pedal the other day. Got it out on open road, got on it, started missing bat at 3000 rpm and above. Check engine light started flashing for about 5 sec. Runs fine under normal driving conditions. Where do I start?:confused:

Go get the codes read at AutoZone

I was having a similar problem in my 98 with the 4.6 in it.
At low revs my truck felt very 'choppy', like i was running out of gas or somthing. My check engine light would flash, then just stay on. I took the truck to the local dealer and had it analized. The service manager told me that in the 98 body style, (so i guess he ment all 97-2003) has a problem with the cowl in the hood allowing water to run into the engine and accumulate around the number three cylinders spark plug. He said that there is not much that could easily be done for this.
He also said that it could be that my auto tranny needed a fluid flush. I had the flush done and ever since it runs great....
Hope this helps..:fyi:

Thanks Johngs & mudcat1985. Going to Autozone in the morning. Will check for water at #3 cylinder, but no auto tranny here, 5 speed. Will post outcome. Thanks guys!

Went to the zone today! NO CODES REPORTED!!! They suggested new plugs. Will try that after i get back from Atlanta this week. I hope it makes it down there and back :(

Bronco,

i have a 2000 f-150 w/5.4L. while on vacation it started running rough, especially when climbing hills or fast acceleration. went to a local dealer and had diagnosis. stated it was a "random misfire" on the #3 cylinder(curious huh). had the plugs, wires and coil packs replaced and a fuel system flush(injector flush). set me back some cash but it ran like a top after that.

i also read a thread on here about the MAS. cleaned it, reset my computer and actually gained some performance.

just my $0.02 worth.

Took mone to the dealer the other day, same as yours boilerjunkie74. New plugs, wires, & fuel filter and all is well now. Set me back $420!!!!!!!!!!!!! About had a heart attack when I seen the bill. There ought to be a law against that. Everything on these trucks cost an arm and three legs :eek: to fix. Gonna sell it and get me a horse!!!!