the truck is a 90 f150 with the 5.0. i have replaced the 02 sensor and the map sensor and all vacuums are hooked up and good. problem is the truck still gets an erratic idle when it park at random times and same with when you come to a stop it will start to erratic idle/buck when in drive at a stop light and start lunging the truck forward. also whenever you are going under 10 and take turns it keeps dropping extremely and wanting to stall(sometimes it does) iacv is good also. what am i missing here?

 

sounds like the plenum/intake gasket is bad. check it for leaks. its really not a big deal to fix. They go bad on those motors.

 

already checked when i got the exhaust leaks fixed

 

Could be your EGR valve is hanging open. That will make it idle real bad and want to stall.

 

Those engines can have crossfiring. If your sparkplug wires are going bad and if you have wires laying over top of each other they can crossfire causing irregular ignition on multiple cyls. Just something to check out, I remember having it happen on several old V-8s I had over the years. Check your sparkplug wires.

 

Does the truck 5.0 use the same salt and pepper shaker connectors behind the intake as the Mustang? Those are common symptoms for the Mustang when corrosion forms in them.