1999 BLAZER,4WD,AUTO.,4.3 In the morning, engine starts and idles fine, but when you take off from a stop the engine "stumbles" until the engine is hot. Runs fine after that. Park it and 8 hours later runs fine. Next morning stumbles again. Is this a fuel injector/regulator issue? The temperature issue has me wondering. It has a new MAF and the throttle body has been cleaned and other items changed recently.

 

maybe a leaking poppet and its running rich until it can burn the excess off? time for a leakdown test.

 

mine did the same thing except I changed spark plugs and wires and it was doing it for a second but then it was fine. Then I changed the mad and it runs flawless. I think what you mean by stumbles is missing if it has a missing code then it’s the plugs or wires, if it has a lean code put some seafoam green in the glass tank half full with some new plugs and wires and your stout. But cylinder 4 and 6 is a bitch to get to. You have to take the steering rod off but make sure you mark it before you take it off

 

Cylinder 4 and 6 are on the passenger side of the engine and are extremely easy compared to the drivers, you must be thinking of cylinder 3. Get a 5/8s boxend and get ready for a fight because plugs like to get stuck in right quick.

the cylinder order on a 4.3 in order front to to the firewall is Passenger side 2,4,6 and Drivers side 1,3,5.