92 s/15 jimmy problem

[tinkerer]

Hello again, I still have the same trouble with my Jimmy. It started running rough one day and the service engine soon light kicked on then before i got it parked in the driveway the light went out and it ran great. So i drove it 15 miles one way with no trouble. But on the way back light came on again and ran like crap again. I have checked plugs, wires, cap, rotor, coil, fuel filter, egr valve and tried jumping a and b terminal in diagnostic conector. The injector is around 6 months old and does not leak and appears to be working fine. Only thing i found was it will not give me any codes not even a code 12 does not flash at all. It does run just not very well and after a few minutes idling it starts to lope. The light obviously works or it would not come on when it is running. My thoughts are in the computer itself or the chip in the computer. Anyone have any other ideas?
Any other ideas would be appreciated before I have to break down and spend the 100$ on the chip or the computer.
1992 GMC Jimmy s/15 Blazer body style 4 Door 4 Wheel Drive
4.3 Vortec CPI injection
Automatic trans with overdrive

[Neilis]

With those CPI's alot of stuff can go bad.

On my 94 blazer I had the same problem. I ended up having to change the injector, and Nut Kit. The injector was the main problem but the nut kit was leaking fuel also. And if you are already inside the intake. Best to change both. GM parts ....Injector-$480.73. Nut kit-$77.82. Gasket-$13.39. Maybe that will help on yours. The only other problem I have is carbon sticking the EGR valve open. It makes it run with a lope.

[Tazmania575]

It is my understanding that if you dont get even the "12" code then chances are you need to check the computer. This was told to me by three mechanics, Chevy, and my repair manual.