I have a 94 Blazer with the 4.3, w vin so it has the spider injector (cpi), When it is cold it runs great, idles smooth, starts quikly, but when it warms up it starts to run bad, as if it is missing on a couple cylinders.
It doesnt do it when it is cold. I have replaced, plugs, wires, cap, rotor, the injector assembly, the "nut kit" fuel supply lines, and intake plenum gasket. Pulled One code out of the computer. o2 sensor lean. The fuel pressure reg. was previously bad, that is why I replaced it, it was bleeding down and making it hard to start until the fuel pressure built back up. Any advise would be a great help.

 

So did you replace it?

 

Yes, changed it out when i did everything else.

 

any ideas people?

 

There should be 2 temp sending units, one for the gauge and one for the computer. Check and make sure the computer sending unit is working. I would check the plugs, you should be able to see if it's rich or lean since you just replaced em. I am no expert on the sensors but since you replaced all the internal injection junk it sounds like it could be a temp related sensor. You could always do a pressure test on the fuel line, never know maybe something messed up on the parts swap.

 

I am having the same problem except the following. If I give the pedal half way to 3 quarters it starts and fires, runs/idles rough 600-500RPM give it throttle rpm 1200 and up runs smooth no misses.

New Tank and Sending unit. Can I clean the EGR? Start their and work around.

1997 Jimmy 4.3 only 30k on the motor being doing it since new.

It used to start easy on cold starts. Hard on Warm starts. Now it is hard on cold too.

Best to all

 

I would deff. Pull the egr and clean it. Make sure there isn't any carbon built up. Since my issues I have been running a seafoam treatment just through the intake to break up some of the carbon to keep from excessive buildup. The way I ended up fixing my problem with the running issue is by unplugging the o2 sensor. Left it unplugged and no probs. Since. Yours sounds like a cpi unit or the "nut kit" leaking.