1993 S10 Blazer 4.3 vin w stalls after engine warms up

[elkhunter63]

1. When engine is cold you can step on gas and it runs great.
2. When engine is warm you step on gas with rpm about 2500 and engine starts running rough and dies. It usually starts up again fine but dies when you step on the gas.

Here is some history of my blazer. This summer the Blazer died and didn't start. I replaced the coil and same trouble. I replaced the fuel filter and same trouble. I replaced ignition module and fixed the problem. I also replaced the cap and rotor. I have 215,000 miles on my blazer. I am getting no codes on my computer. Two years ago the Egr valve was replaced.

3. Tested fuel pressure at rail and it was 59 lbs. When it started to quit it seemed that the pressure was dropping below 55 lbs so I replaced the fuel pump with a Bosch fuel pump and screen. My hat goes off to the guys who work on cars and trucks for a living. The removal of the tank and putting it back in wasn't fun. Same trouble. With the new fuel pump the pressure stays at 59-60 lbs even when it dies.

4. I removed my Intake manifold tuning valve to get a look at my pressure regulator to see if it's leaking or not. This trick I got off this forum. The side by the regulator was all nice and clean. So I replaced the regulator and the gasket. I put it all back together this morning. I warmed up the engine and same trouble. Note: This forum was a great help on doing this procedure with nice pictures to follow.

5. I know I am shotgun troubleshooting but at some point these parts will fail anyways with the mileage I have. One good thing is I am getting to know my Blazer intimately.

6. Any help would be appreciated.

[Blue Bowtie]

After all the fuel system repair, what is the standing fuel presure?

[elkhunter63]

Originally Posted by Blue Bowtie

After all the fuel system repair, what is the standing fuel presure?

It is holding a steady 59 - 61 lbs. Right now I am working on going into the Field Service mode, with the engine running shorting pins a and b. When I do this the blazer will start and run good in the open loop mode. The Mil flashing 2.5 times per second. When it goes into the closed loop mode thats when I seem to have the problem. The Mil goes off and stays off and the blazer dies. I am using a Chiltons repair manual and when the mil is off it says it is running lean. The manual also says it starts off in the closed loop mode until the 02 sensor is fully warm and then the control module decides that its feedback is reliable and then goes into the closed loop. Could the 02 sensor be causing this and be bad? I think I am leaning towards replacing the 02 sensor, what do you think? Thanks for responding.

update: I Pulled the 02 sensor plug. I went into Field service mode and waited for the Blazer to die. It stayed into open loop mode, and after a few minutes warming up it started doing the same thing. Back to drawing board.

I never did get a code from the computer with o2 sensor unplugged. I didn't run it for very long either. FYI

I'm in over my head so I am punting. I've set up an appointment for Monday at a local shop.
I'll post what he found.

[duke350]

Have you found anything out on this?

[elkhunter63]

Originally Posted by duke350

Have you found anything out on this?

I got the truck back last night, I had to get the spider replaced. I also had him put a nut kit in while he was at it. The blazer seems to be running good. Thanks