Hey guys new to this, just picked a 1998 F150 4.2 V6 159,000 on it. Love the truck so far but it has an idle problem I need help with. Runs Great but if I'm at a light for over a couple of minutes it starts running real rough, if I put it in nuetral it smoothes out just like that without even touching the gas. I have codes P0171, P0174, and P1506. I know to check for the vaccum leaks and I ohm checked my IAC and it checked out. I thinking of changing the intake gasket, just because of all the trouble I have heard abouth these gaskets. Is this a job that can be done in a day? I am not new to engines, but I havent worked on too many newer model motors. Is there something I should be checking before gaskets and leaks? Any help would be greatly appreciated.

 

I have the exact same codes that you do on mine. The lean codes have been there a while I believe do to the bad gas mileage, while looking for leaks to fix them, I ended up getting the P1506. I am at a loss right now to on what to do. All the vacuum lines appeared to be ok. I may try pulling off the top half the intake to check under it.

 

See if you can read the build date on the sticker on the driver's side valve cover. If it's before 1/15/98, get yourself an improved gasket kit - change the upper and lower intake gaskets and the front cover gasket.

 

I did that back in '03 and the dealer screwd the headgasket replacement up so bad they place a new long block in the truck. I know the intake/injection system though was off the old motor.

 

Get this fixed?