At wits end, need help guys!

[CajunGMC]

I've got a 94 gmc 1500. back in june I replaced the motor and trans. 4-bolt main, bored .30 over, mild crane cam, msd dizzy, rebuilt tbi, new injectors and adj fpr, new fuel pump, and new sensors. Let me tell ya she ran like a scalded ape! That is till last week. now when you fire her up, she'll idle fine for 3,4 min then she starts loping and dies out. If you drive her she'll bog down then rev up for a couple miles then alls good. shut her down then fire her up, same **** all over. doesn't matter if it's hot or cold. all vacuum lines are new, map sensor and harness check good. fuel press is spot on. Could the ecm be going out? Any and all ideas very welcome. this is my dd. THANKS

 

[oohunter04oo]

I'd start with a ignition coil. Mine did that when the coil went out. It had spark, just not enough. Only difference with mine is I had to advance the timing to start it.

 

[CajunGMC]

Bought a new msd coil when I built the engine. Can't be bad. Still, what the hell, went and dug out my old coil and switched them. BOOM!!! Back to her old self! So msd gets a call in the morning. Hunter, from one Louisiana brother to another, THANK YOU.

 

[ChrisAU]

MSD = Might Soon Die

 

[CajunGMC]

Chris, I believe you are correct sir.