95 sub 5.7 tbi

[dab7778]

put a motor in my 95 sub..5.7 tbi...have been driving for about two months and now im having a problem....if its been running for about 30 to 45 min when i hit the gas it dies out..wants to completely die and black smoke pours out the tailpipe....if i feather it just right it will stay running....just did iac and still do this...any ideas....does that little flapper in air cleaner tube have any thing to do with this...any help would be great....thanks dan

[2000CAYukon]

Black smoke means you are running rich. 1st thing to check in the engine coolant temp sensor (in the intake manifold near the tstat housing). If you have a scanner, you should see what temp it is reporting to the ECM.

The exhaust heat riser should be closed when the engine is hot. On my 90, it stopped working a few years ago and I wired it closed since I don't live in a real cold climate.

//2000CAYukon

[dab7778]

ok thanks im goona change that either way its cheap enough anyway....have been watchin temp gauge last couple of days and have noticed that as soon as i start it in the morning it jumps up a notch...ill let you know how i make out...

[dab7778]

as for the heat riser if i do wire it shut what differnce will it make as i live in ct and we do have the cold weather????

[j cAT]

Originally Posted by dab7778

as for the heat riser if i do wire it shut what differnce will it make as i live in ct and we do have the cold weather????

the air intake manifold heat riser needs to work properly ...this device tries to keep the air entering at around 100deg F .....

the reason is when it is humid out and the temps are around 25-50 deg f you will get intake ice build up this causes poor idle , stall, hesitation, lots of black exhaust .....not good ...

I have used fiberglass insulation wrap on the pipe to aid in the intake to get the proper temp faster this does help...but if its rusted or damaged you must get another that works from the scrap yard ...

[dab7778]

Thanks for your help guys....it finally threw me a code last nite and sure enough it was the coolant temp sensor....changed it out and all seems good so far......