4.0 Wont Idle

[90jurassic2]

I just swapped a new 4.0 into my truck. I heard the motor run before I started the swap. I just tried to turn it on after many a words and thrown bolts only to have it idle up to about 3K RPM then it tries to die.

On the passenger side manifold the two middle bolts are stripped out on the head (I didn't do it). I figured this would give me an exhaust leak, but not enough of one for it to die.

I've tightened the collector bolts down as much as they would go, and the flanges seem to be pretty well seated.

When it does run, there exhaust smoke the comes up into the cab.

Any help is appreciated.

 

[90jurassic2]

I got it to run roughly down my block. First time I drove it in a month. There's a lot of smoke, I'm guessing exhaust? I know there should be some coming out of the heads but I didn't think it would be this much.

 

[RonD]

High idle reads like a vacuum leak.
Check all the intakes hoses, and make sure the intake, upper and lower, got all it's bolts tightened up.

Leaking exhaust manifold won't cause the engine to run rough until it warms up and the O2 sensors take over the fuel/air mix.

When engine is cold, computer(PCM) runs a pre-set fuel/air mix, based on the throttle position sensor(TPS) and MAF sensor(mass air flow)

Lots of grey smoke could be a rich mix, could be a leaking FPR diaphragm(fuel pressure regulator) sucking raw gas into the intake, check its vacuum line, if it smells like gas or has gas in it then replace FPR.

 

[90jurassic2]

It started to idle fine after a run around the block. I'm guessing it had to get some more gas in its system. I don't have the air filter on, so I know it wont run tip top shape. I'm just worried about the smoke. It's coming out from where the two threads are stripped on the head. I just have to take the head into a machine shop and get them Heli-Coil'd.