cupwalker

new problem.... runs great,idles great cold and in gear. as soon as i put truck in park or neutral it dies instantly. is there a vacuum line im missing or is the o2 sensor bad? if i can get this problem fixed i should be completely done with the engine and then i can start on the body and interior.

Bluegrass

I assume you cannot start the motor 'hot' in either Park or Neutral.
Or does it fire if you hold some throttle on it?
Your not being completely clear.
It makes a difference to kinow this info because the differences in running statiegy is different.
Could be a trans switch, TFI, an IAC etc depending on specifically how it acts.

cupwalker

it will start hot then dies. i can keep it running with throttle. there is no problems when the truck is in gear.

Bluegrass

You have some kind of problem with the IAC controlling the idle air bypass in neutral.
It either sticks, has a plugup issue or even a mounting issue.
What is unusual is you say the motor idles ok in gear. That is oppisite what you would expect.
What is the idle rpm in gear?
It should be no less than about 600 rpm in gear and about 50 higher in neutral.
Has the base idle (on the throttle plate position stop) been moved?
Here are some things to check out.
1. The throttle plate should be open just enough to allow the motor to idle at about 500 rpm without the IAC plugged up. There is a setup spec for this.
Once that has been established, the IAC has the needed range to work over and maintain the idle according to a table in software.
This spec operation needs to be close so cold weather starts and cold idle is problem free.
Good luck.