Can't keep truck running when at idle

[Red 83]

I am having trouble keeping my truck running until it is completely warmed up. Every morning and evening when I start it up, it will run for a couple seconds and then die. It will always restart, and it's ok if I hold the gas pedal down a little. As soon as I put it in Drive or reverse the RPMs go way down, more than it does when it's at operating temp. It will also tend to sputter/run rough when sitting at a stop sign/light not long after it's been started.

 I have also noticed that it will only start in Park, not neutral.

Today, I got 10 miles out of town, it was at operating temp, and when I came up to a stop sign, it ran really rough (almost died) and the oil pressure gauge was reading 0. As soon as I pulled away, the oil gauge went back to normal (40 psi at 55 mph).  When I got home, I let it idle a bit to see if it would do it again, and everything was fine. When it is at normal temp, it idles fine in Park or Drive.

Any ideas?

[Lt.Del]

you don't say what kind of truck you have, there is a giant difference b/w carb and tbi.  judging from your name, it may be an 83, therefore carb.  Your choke may need attention.
A vacuum line may have popped loose as well.
As for not starting  in Neutral, your Neutral safety switch on your steering column, under your dash may be out of adjusment or bad. 

do you still have all your smog stuff attached?  check your egr valve (any carbon buildup?).

[Red 83]

Sorry, forgot to give the vital information. Yes, I have a 1983 C10. It has an '84 crate 305 with 4bbl carb. I just had the engine replaced, so the vaccum lines should be fine. I was wondering about the neutral safety switch, is it very hard to replace?
It seems like once it's up to opperating temp (or restarted while the engine is still somewhat warm), it runs just fine. I would even go as far as saying that it idles a little fast.

[Lt.Del]

it isn't hard to replace the neutral safety switch, but, that isn't your idle problem, it is your 'can't start in neutral' problem.

i say adjust your choke.  Also, did you get a new egr when you got a new engine?

[bake74]

     Your engine might be new, but the idle problem you are describing is a typical vacuum leak problem.  When cold they idle like crap, when warmed up they idle just fine.
     Could be some of your bolts loosened up, use the carb. spray trick and eliminate area's for vacuum leaks, do this while it is cold though so you can hear the change in idle speed.
     I think yourself and SgtDel have the neutral problem figured out.

[Blazin]

It could still be a vacuum line. Just because you had the motor replaced doesn't mean the lines are good, or that they were installed correctly, or that they haven't fallen off.

[jaredts]

Once you're certain that you've fixed any vacuum leaks, you need to adjust the choke and high idle speed screw.  If it idles fast when warmed up you need to adjust the idle screw as well.  Maybe they just didn't dial in your choke and fast idle.  Is this a new or rebuilt carb. or the an old one?

[Red 83]

Awsome, thanks guys.

It'll have to wait until I get home early some evening or next weekend. Winter finally showed up in Iowa! 5-8" of snow as of now. We have so many vehicles that both my trucks have to sit outside in the snow. Time to go do some donuts in the vacant parking lot!