Chevy 350 Check engine

[mikeswrangler]

Ok all you chevy guys (if there is any on this board, haha) I have a 91 2500 with the 5.7. Once it is warmed up it runs like crap, bad accel/sputtering, nothing smooth about it. Check engine light comes on and off. These were the 2 codes that were pulled up and I checked online and found this info. Now is closed loop for the oxygen sensor during first start up of a cold motor, or while running at operating temperature. I figured closed to be at operating temp, but im not positive. I used to have a maxima and I know knock sensors used to go on those and were problems and the motors would run like crap but never experienced it. Whats your take on the codes. Replace the o2 and knock sensor only like 70 bucks.

Codes:

43 The ECM did not detect a knock signal during near wide open throttle operation, or the knock sensor voltage was above 3.62 volts or below 1.44 volts for 0.5 seconds.

44 Oxygen sensor voltage was under 0.2 volts for 50 seconds of closed loop operation.


Thank You!

 

[anony91xj]

Disconnect the coolant temp sensor and see how it runs. I believe Chevy's PCM will sub a value when the sensor is disco'd, could be wrong though. A running problem that's temperature related is likely to be a temp sensor though, they have a critical role in determining A/F ratios.

 

[jeepdude10000]

closed loop is when your O2 sensor is bad, and your computer is running in default mode.

 

[MJmk]

Common problem on these engines is for the trigger wheel on the distributor shaft to become loose and cause timing changes. Pickup coils also seem to go out a lot too. Check your base timing and see if it has moved. Don't forget to unplug the timing set connector! That may be the cause of the ESC code 43. If the timing is retarded, the ECM may not be able to advance the timing enough to cause a knock during the test cycle. Good luck!

 

[19CHEROKEE89]

replace the sensors and you should be just fine.

 

[mikeswrangler]

It was a coolant sensor check engine code 15, runs great now