I have a 1999 F150 Supercab with the 4.6, it has 205,000 mi on it. When I purchased the vehicle it had a terrible miss and barely ran. I changed plugs, wires, fuel filter and air filter (the plugs may have been original, the electrode was burned flat on all the plugs). The truck runs much better, smooth idle and revs easily when not under load, however, when in gear it has a dead spot just off idle if you mash the gas and it doesn't see to pull as hard as it should. It runs the truck right up to a 100mph, just not as quickly as it should?? Any ideas or comments please!!

 

With 200k, and no real problems but power. I would count my blessings and run her till she drops. Even with the best maintanence, at 200k that puppys got a little wear everywhere. Not much you can do about wear. Maybe a rebuild or a reman or a crate. My 97 has 140k. It don't have as much pep now as it did at 90k. As long as its running decent leave it alone and enjoy.

 

check EGR ports clean the throttle body clean the MAF clean the injectors. and check the compression

 

i will echo the tb clean and egr ports
mine has 201k and both ports were 100% plugged
tb was really gummed up i used almost 5 cans (4 1/4)
ran like a new truck afterwards

i gave myself plenty of time for the job, ended up using drill bits to help clean the plugged ports.

use tools that click or hold themselves together ( have releases)
the lower intake has lots of hiding places for tools and sockets that fall off.

 

When you are done cleaning try changing the front O2 sensors.

JMC

 

you know i'm still running my original o2 sensors (at 201k miles)
truck always averages about 17+ mpg ( i have the records)
but lately my mpg have averaged 19+ with several over 20

i think i finally got the truck broke in