Yukon still stalls. Help

I posted a while back about my 98 Yukon that would stall like it was starved for fuel after it sits for a while. It only stalls and jerks for about 5-10 seconds after the car has been sitting overnite or sitting all day. I replaced the fuel filter and fuel pump assembly. I have had the fuel pressure checked and we have checked all the sensors by putting some off a core we had on the motor just to see what it would do. Now the guy I have working on the thing thinks it might be the big injector unit and wants to try puttting one off a core motor on it just to see. The engine does not set any codes but when it is hooked to the computer it is showing that it is running rich when you first start off. I need help. This thing is driving me crazy. Any ideas would be appreciated.

I posted a while back about my 98 Yukon that would stall like it was starved for fuel after it sits for a while. It only stalls and jerks for about 5-10 seconds after the car has been sitting overnite or sitting all day. I replaced the fuel filter and fuel pump assembly. I have had the fuel pressure checked and we have checked all the sensors by putting some off a core we had on the motor just to see what it would do. Now the guy I have working on the thing thinks it might be the big injector unit and wants to try puttting one off a core motor on it just to see. The engine does not set any codes but when it is hooked to the computer it is showing that it is running rich when you first start off. I need help. This thing is driving me crazy. Any ideas would be appreciated.

This sounds like a fuel pressure regulator to me. With a pressure gauge hooked to fuel rail, what does it do when you turn the engine off? It might drop a little but it should hold pressure.

If it drops to zero over time, the fuel pressure regulator is probably bad. Do a search and you will see how common this is.

//2000CAYukon

when does it happen ? sounds kinda like IAC (idle air control) valve acting up. may need to clean that along with throttle bore/plate as regular maintenance item. tune up recently ? if not i would start with that also before dumping money. most sensors trigger check engine light if reading out of specs.