Missing '93 S-10 Blazer; 170,000 miles, 4.3 l w/ CPI

JRITTER18

MEMBER
1993 CHEVROLET

I have no codes currently. Previously I did have a knock code. When I look at the PCM sensory output, I can see the O2 sensor going out of its normal range of .1 to .9 volts whenever I accelerate. I have already replaced the sensor.

Could a leak in fuel system within the air manifold be causing the missing condition and the O2 sensor to go off the scale or is normal for the 02 sensor to off the scale during acceleration?

The problem did seem to get worse after the fuel injector system was cleaned (sujected to high pressure at the dealer.)

The only time the PCM is in closed loop mode is when the O2 system is off the scale and shortly therafter. Otherwise it is in open loop.

See picture for sensor output.

3 Replies

2CARPRO JACK

MECHANIC
11,533 POSTS

The CPI's were a miss waiting to happen. If there are no vacuum leaks then hang a fuel pressure gauge on it. Pressure should jump up when the engine is revved, if not probably the pressure regulator, maybe pump if it hasnt been done yet. Also had big injector problems and cleaning them rarely helps. When the reg pops it dumps raw fuel intothe rear cylinders, that may be the erratic o2 reading. However o2 sensor jump from rich to lean constantly, I would start with the injection