'ol chevy won't stay runnin
 

i've got an '88 k2500 I just put a rebuilt 350 in and it runs and idles fine but as soon as ya put it in gear it wants to stall...unless you feather the throttle. I replaced the module on the distributer, the throttle position sensor, electronic spark controller and various other sensors, could i have a bad computer??

thanks,
-Justin

This is going to be hard to check unless you have the equiptment, but it sounds like there could be a problem with the IAC ( Idle Air Controll)

Base idle and Timing are 2 of the main problems with low idle.
The ECM takes nearly 20 ignition cycles before its willing to allow a signifigant change in idle strategy. Meaning you could have a failed IAC which will set no codes in many cases and will not allow the ECM to increase the idle rpm.

Double check your timing (retarded timing will cause low idle)
Take the air cleaner off, start the engine. Once the idle settles down have another person put it in drive. Do you hear a noticable difference in the noise at the throttle body? If no, the IAC is not changing. It's job is to allow a controlled vacuum leak through a passage at the right rear of the throttle body. If this valve is stuck or not working at all, you'll have no change in RPM.

When checking your timing, you should also check your base idle setting. This setting shouldnt change and rarely needs to be adjusted unless someone has already tried to adjust it.

I already checked it...iac is good.....i don't know what else it could be

How does it run otherwise? Does it feel like a misfire at idle or is it smooth right up until it dies?

One thing that comes to might when you say "feather the throttle" is a bad MAP sensor. Check vacuum to the map sensor, should be a constant/solid vacuum!
Leave the line off and plug it, keep it running as best you can. After 20 seconds the ECM will go into field service mode which rejects any sensor readings. If you have a bad map sensor, this will cure that problem. Of course this means you'll have a Code 45 and 32 (map voltage too high) but you can just reset the ecm by disconnecting the battery for 10 seconds and clear those.

Did you check the IAC as mentioned? Unless your timing is so far off it wont run, you've got some problems.... ECM is capable of holding an idle on 6 (of 8) cylinders and 1 injector.

Did you check the base idle? what did you set it at?

Next step is to get the scanner on it and see what the IAC is doing. You'll also want to look at blocklearn (adaptive strategy), which will tell you if you have a fuel trim problem or if a sensor is reporting some crazy readings.