This is a tough one for me. I have a 1994 S10 blazer with the 4.3L V6 that is running horribly rough. One day it decided to run terrible with no warning or lead in. It will barely start and run and with very little power; it wont even spin tires on gravel--it has a very methodical miss to it. The following is a list of things that I have replaced or checked out good.
Fuel Pressure--Holding 60psi.
New Fuel Filter
New Plugs and Wires
New Cap and Rotor
New Spyder injector--along with the nut kit.
Compression test on all six cyliders--150PSI
New Coil
New EGR Valve
New TPS and MAF sensor.
I checked the fuse box--all looks good.
I checked things for obvious signs of decay--nothing seen.
Still runs horribly and the exhaust smells like straight un-burnt gas. I pulled each plug and it looks like all six are getting plenty of spark when grounded.
What am I missing guys?! I even had a OBDI machine hooked up and it said everything was fine. Can anybody help me with this old girl? I have already exceeded the value of the vehicle in worthless repairs alone. Thanks in Advance !

Brannan

 

Had somehing like this happen with my '93. Couldn't figure it out, and by dumb luck found a detached vac line on the bottom of the intake hose right by the air box. I'm sure you looked at it, but double check. Never know.

 

Thanks, I will double check on that kendog. Anybody else?

 

Does Anybody else have any clues? I am still stumped. Does the engine coolant temperature sensor help regulate fuel output? If so and if it was bad could it cause my truck to be this bad off? Also, what about the Ignition Control Module...if that was bad would I be getting any spark at all?

 

is the timing right? wires all going to the right plug?

 

I loosened the distributor lock bolt and rotated the cap a half inch either direction while the engine was running. The symptoms improved slightly when timing was advanced, but not by much. I should put a timing light on it, but is it possible that it could have jumped timing that badly ?
Also, could the computer be to blame?

 

Next time, you should do some diagnosis before you replace all those parts.

 

I wouldn't suspect the computer. how many miles on the engine? Cam timing?

 

I had one and the MAP sensor was bad, changed it and it ran fine again.

 

You should check the exhause to see if you getting good flow. I once had a clogged catalytic converter (CAT). I checked it by putting my hand over the exhaust tip and having someone punch the gas, I felt very little exhaust pressure. I punched a hole in the CAT and it ran great.