I have a 1994 Chevy S10 blazer with the Vortec engine. Several people have looked at it and no one seems to figure out the issue. It will start and idle fine. when it gets warm it starts to miss so bad it cant be drove if you barely give it gas u can make it back up the rd. I have replaced rotater button, distributor cap, and module. Put coil on didnt help so put old one back one. Tried a new throttle position sensor didnt help. they have unhooked the EGR and drove it didnt help. Its not the oxy sensor. Any ideals of what else it could be??? Also have replaced fuel pump and strainer and the inline fuel filter.

 

How do you it's not the oxygen sensors? Were they replaced? Also, do you have a check engine light? When an electronic fuel injected gasoline engine warms up, it enters closed loop and calculates long and short term fuel trim with the oxygen sensors. If the truck runs fine when cold (open loop: looking at the throttle position sensor, MAF sensor if your truck has one, and MAP sensor) then the problem is probably not mechanical.

If the truck can't run correctly in closed loop it's either fuel trim problem, crank sensor problem, even a faulty computer. Try disconnecting the battery and leave disconnected for couple of minutes to reset the computer, if that doesn't work drive the truck long enough to get a check engine light (note: some faults are not going to set a check engine right away and will have to occur twice before lighting the check engine light).

Also, if you can adjust base timing with the distributor, check base timing and adjust it to factory spec. And on the issue of ingition timing try doing crank sensor relearn; my truck ran a little rough (not as bad) until I did a crank sensor relearn, but I had to use a scan tool to get it to relearn the crank sensor.

 

Failing as it warms up could be an ECT sensor problem or a problem with the upstream oxygen sensor. If the proper ECT signal is not received by the PCM, it will command the injector full rich. This could be a faulty sensor, or wiring to the PCM. If the oxygen sensor signal is not received by the PCM, the PCM will command the injector full rich. This could also be a faulty sensor, or wiring to the PCM. The PCM's on these things are almost bulletproof and rarely fail. Could be the thermostat is stuck open, which will also cause it to run rich. Could be a fuel delivery problem, but doubtful if it only acts up warm.

 

Reading through the info that has been posted on checking the fuel delivery system. I did not see anything on a 1996. Is there a fuel reg or a fuel pressure switch on this model. 1st one I have ever owned , so far like everything about it.

 

1994 & 1996 use completely different fuel delivery systems. To avoid confussion, please start a new thread with questions regarding your 1996 here: https://blazerforum.com/forum/newthr...newthread&f=41

Thanks