I have a 99 blazer with a 4.3. I am trying to diagnose a bog under heavy throttle. If you slowly crack the throttle it will rev fine, but it you gun it it will fall flat on its face. The only code I have is a p0102 low output Maf. I cleaned the sensor and the code hasnt came back. I verified fuel pressure 49-55 lbs and engine vacuum is around 19-20 hgs with a steady needle. I pulled and cleaned the egr valve also. Another thing is the idle is erratic at times fine at others. I found that air temp sensor was unplugged and when I plugged it back in the engine died. It will not run with the air temp sensor plugged in. Any help you can give is greatly appreciated this thing is driving me crazy.

 

Have you checked the TPS Throttle Positioning Sensor?

 

If you plug in the temp sensor when it is not running, will it start?
If not the sensor or wiring is probably bad.

When I had a bad fuel pump (cheap non-Delco brand), my pressure at idle was fine, but when I revved the engine in gear and the brakes on, the pressure would dip and the engine would falter. New Delco pump fixed it.

 

There's your problem. Key on, engine off, fuel pump running: Pressure must be 60psi to 66psi and must remain above 55psi for 3 to 5 minutes after the pump shuts off. Here are the details on how to test the fuel delivery system: https://blazerforum.com/forum/tech-a...agnosis-23038/