I have a 99 gmc 1500 sierra with the 4.3 litre v6. Last week it shuddered while i was driving it but kept going fine. That afternoon I drove it and it did it again and it then stalled only to start a couple times then stall again? Needless to say I had it towed home then to a tech to have checked. I assumed it was the fuel pump (common on gm vehicles) so he checked it and said thats what it seemed to be. I bought a new ac delco pump assembly and fuel filter and he installed it. Now it runs but still does the same thing?? Also it never shot a code when it stalled prior and only shot a misfire code after pump install? Anyhow he tried a crank sensor and ignition module (neither worked) he swapped relays, ran for 3 HOURS!! then stalled again and is doing the same thing as initially??? Still NO codes present in the system??? Please I need some help with this, I was thinking of two things ECM or ignition switch? When it runs it runs great, no missing hesitation ect.. but it still intermittently stalls...PLEASE any one help me with this aggrivating problem. :banghead: Thank you all in advance.

Welcome to AF, When it stals do have spark, will it start if you spray carb cleaner into the intake, how and how long does it take to restart it, lots of info left out here. lots of problems with burnt connectors at the fuel pump harness at the tank also.

A very common problem on those (and other GMs) is the EGR sticking open which causes the exact issue you describe. Next time it happens give the EGR valve a whack with the handle of a screwdriver. If it changes or helps, replace the EGR.

Welcome to AF, When it stals do have spark, will it start if you spray carb cleaner into the intake, how and how long does it take to restart it, lots of info left out here. lots of problems with burnt connectors at the fuel pump harness at the tank also. I'll check those things next time I start it.

A very common problem on those (and other GMs) is the EGR sticking open which causes the exact issue you describe. Next time it happens give the EGR valve a whack with the handle of a screwdriver. If it changes or helps, replace the EGR. But why not shoot a code?? I'll check it though. Thanks