Feather throttle to keep running until reaching operating temp
 

502 mag efi that will not stay running without me pumping the throttle a click up and down until it reaches operating temperature. Once it gets up to temp out of startup mode it will idle perfectly and run like a bat out of hell. Until then it just wont stay running. It's almost as if it is starving for air because the IAC motor is wide open but you can smell fuel at the pipes. Idle air count / secondary needing adjustment? MAP sensor?

Possible bad Coolant temp sensor or shorted or bad connection, Possible bad MAP sensor or shorted or bad connection, Also could be both. Is this motor very hard to start initially ?

Scanning the motor sure might be able to pin point you in the right direction especially showing and fault codes and or fault history. Clean your flame arrestor very well also, restricted intake air causes rich conditions and poor running conditions as well.

Motor fires up perfect. Its when it reaches around 120 degrees this happens up until operating temp of 160. I will take a look at the coolant temp sensor I didn't think of that. I will also clean the arrester. I have the scan tool ordered so I can check the parameters. I am going to go over all the connections as well to the sensor. Thanks for the tips. I will report back.

Ok so I got the scan tool and tuned the IAC follower count. Now it was fully warm and the IAC follower when warm is at a perfect 40. Warming up though it is at like 3. Do I need to be setting the count as it warms up or at operating temp when its out of the warm up mode? I can not rev the engine at all in warm up and tonight running it on the house I could not get the temp up past like 135 degrees. I am almost there it seems. Thanks!

So this was the result of improper fuel pressure from high pressure pump going bad.