Duces2you

I have a 2002 4.6L f150 and I have been having a problem with it's idle since I bought it 4 years ago.

I have done everything over again in terms of cleaning out the intakes, oil, fuel filter, air filter, sparkplugs, MAF, O2 sensors, fuel cleaner, vacuum lines and fuel cleaner. My truck is well taken car of but it just has this really screwy idle and it has like a very rough but slightly shake in the idle and motor every 4 to 6 seconds. Its not enough to act like it's gonna stall but it is noticeable if u are looking for it.

Also the rpm will go up like 25 maybe 50rpms when it does this little cough for maybe 2 seconds.


What the hell is that? It's driving me nuts! I've hose clamed ever line I could find think it's a vacuum leak. And again my truck well taken care of is there something I'm missing?

the01kingranch

What about your iac?

Duces2you

It's been cleaned and is functioning but never replaced. If u unhook it the truck dives and stalls

Duces2you

**Bump**

white89gt

I don't see any mention of ignition coils... what are you using? what is their condition?

Duces2you

All 8 have been replaced for new 2 years ago and it has made no difference to the idle.I don't mess around with coil over pack and sparkplugs cause my last gen 10 blew out 3 sparkplugs in its life so I keep up on my plugs and packs and change the early.

white89gt

Replaced with what brand of coils?

Duces2you

Motorcraft

white89gt

OK good.

Have you pulled/examined the PCV valve and line?

Duces2you

Vacuum lines are good and as far as I know the pcv are good because they don't act like they are bad. Any tips on what I should be looking for?
I think this issue has messed with my mpg cause on the flat freeway with the cruise control on I still only get like 12mpg when my Manuel and ppl on here in the past say I should really get like 18 some ppl with mods got like 21 is the highest I have ever heard my other gen 10 would get 20mpg on average.