Ok I have been to 4 shops and no one knows what is wrong,

I have a 1994 s10 blazer 4 door 4x4 4.3 vortec that the engin missed really bad. so I had the timing set(was 12 degrees off) the motor ran really smooth for a while with a small miss. replaced all the spark plugs ( #4 was fouled). pulled the vortec valve out and saw that the lower intake was washed, so I replaced the cpi, and the nut kit. so Now the engine runs great. however it will only run for 25-45 min depending on the weather. cold days longer than hot.

I have had the fuel pressure checked reads 56psi and drops to 54psi after 5 min.

these are the things that i have done to this motor
General tune up
Plugs, wires, cap, rotor. pcv, and the air filter.
other
Pcv. iac. Tps tempsensor knock sensor, baro sensor(map)
checked all vac lines (fixed 4x4)
flush X3


is this a Ignition control modual issue? cause the intake feels hot when it happens.

*edit* So I replaced the Ignition control module and still the issue arises. any Ideas?

 

ok so I replaced the pickup coil (runs fine) now its throwing these codes

13 - Oxygen sensor circuit - Oxygen sensor voltage stays between 0.35 and 0.55 volts for 30 seconds when the TPS signal was above 0.55 volts. The engine had been running for at least 40 seconds with an engine temperature above 110? F.

32 - Exhaust Gas Recirculation (EGR) Circuit - EGR open command did not change the fuel mixture when the command was given during off idle operation. EGR opening should cause the mixture to be slightly richer because of the low oxygen content of exhaust gas.


34 - MAP sensor signal voltage low - MAP sensor signal voltage was too low (high vacuum) when engine speed was over 1200 RPM, or the throttle angle was above 21% when engine speed was over 1200 RPM.



Need some ideas where to start.

 

I would look over all of your grounds, especially the ones on the back of the cylinder heads.

Clean your EGR valve.

The MAP sensor could be clogged or have a restricted vacuum line to it. This should be easy enough to check.

Get a scanner that can view live data or record data (ALDL cable and WinALDL are the cheapest combination for this, but a laptop really is required). This will let you see what the PCM is receiving from the sensors and also let you trouble shoot possible wiring issues.