Hey guys i own a '98 f150 with a 4.2l v6 and it has trouble idling when i sit at stop lights for very long... i have changed the plugs/wires, fuel filter, and even the fuel pump....any suggestions?

 

vacuum leak maybe?

 

Any codes being thrown? The 4.2 does have issues with intake leaks at the upper plenium chamber.

 

My guess would be the IAC (Idle Air Control Valve).
Located behind the throttle body back close to the firewall.
Tight spot.
Uses a 8mm wrench. I lost 1 down in the block somewhere.
The second one I tide a small string to. Thank god I did or I would have lost that one too as you have to reach pretty far back.
Idling is very bad when this stops working.
Make sure you take a good look at your IAC before you leave the dealership with your new one as the one they gave me for my 99 was not what was on the vehicle. They were puzzled, but looked at it and gave me the matching one. Has corrected this problem for about a month now.

 

my dad thought the same thing i think were gonna check this weekend so ill let u know how it goes after that

 

Check the rubber elbow on the PCV hose for tears or soft spots. Very common vac leak area.

 

hey guys thanks for your suggestions i'm gonna try a few of them in the next few days and i'll get back to you on what happens...

 

k so like 3 months later i finally got the chance to get it checked out and it was a vacuum line...

 

Which one?

 

not exactly sure, but i had that replaced along with the left abs speed sensor and the sway arm bushing on the left for only $170, not too bad i thought.