Will not stay running when cold. 99 gmc Sierra 2500 6.0

Rick_sea2001 · January 10, 2016

Alrighty i have a 99 gmc Sierra 2500 with the 6.0 the issue I am having is when and only when it is well bellow freezing outside is the truck will start get up to about 1000 Rpm and then fall on its face like its loosing fuel or spark maybe something in the computer telli g it to shut off? Not really sure and I'm stumped on figuring it out.

Things I can remember I have done when the truck won't stay running, check fuel pressure, remove battery cables let it sit for ten mins and try it again, pull the top off the air filter box and try it, fuel pump and filter have been replaced with no change, fuel regulator, and I'm sure there's more that I can't think of off the top of my head also the security light has been on intermittently and I have not been able to figure out why may be unrelated not sure.

Also this past year I have put a new upper end on the motor including heads plugs wires headers sensors about everything except intake and injectors and the injectors were done about 4 years ago when I got the truck. If there is any more information that I missed y'all need just let me know Sorry I know this is kinda long but would really appreciate any advice that will point me in the right direction and thanks in advance!

rjgti · January 10, 2016

check and clean iac on it

Rick_sea2001 · January 10, 2016

Already have replaced it and cleaned the throttle body at least twice

anumber1 · January 10, 2016

I had issues with poor idle and a stumble when partially warmed up. Also the truck smelled rich on cold start. Turns out my MAF was lazy. No amount of cleaning helped. A rock auto replacement cured it completely.

No codes were ever thrown which made diagnosis tough

Rick_sea2001 · January 10, 2016

Ok I'll have to look into that but in my eyes that doesn't really explain why it would only act up when its cold even tho I think that is the only semsor I have not replaced on the truck. Also been doing some reading and kinda leaning towards the paslock system anybody have thoughts on that?