01 Blazer p0300 code

[61_FL_Apache]

Yes. My Ho runs great!!

I did clear the codes many times and 0300 was the only one to return. I only saw 0306 once.

So from this checklist here, This is what I have covered so far.

Common Problems That Trigger the P0300
Worn out spark plugs, ignition wires, coil(s), distributor cap and rotor (when applicable) Changed all
Incorrect ignition timing - Computer does this, I dont think its adjustable. I know the dizzy is in a fixed position
Vacuum leak(s) - No visible broken vacuum lines
Low or weak fuel pressure - 55 psi when tested
Improperly functioning EGR system - have not checked this
Defective Mass Air Flow Sensor - have not checked this
Defective Crankshaft and/or Camshaft Sensor - changed crank sensor.
Defective Throttle Position Sensor - have not tested this.
Mechanical engine problems (i.e.—low compression, leaking head gasket(s), or valve problems - these have not been checked.

[76C10Stepside]

Originally Posted by 61_FL_Apache

Yes. My Ho runs great!!

I did clear the codes many times and 0300 was the only one to return. I only saw 0306 once.

So from this checklist here, This is what I have covered so far.

Common Problems That Trigger the P0300
Worn out spark plugs, ignition wires, coil(s), distributor cap and rotor (when applicable) Changed all
Incorrect ignition timing - Computer does this, I dont think its adjustable. I know the dizzy is in a fixed position
Vacuum leak(s) - No visible broken vacuum lines
Low or weak fuel pressure - 55 psi when tested
Improperly functioning EGR system - have not checked this
Defective Mass Air Flow Sensor - have not checked this
Defective Crankshaft and/or Camshaft Sensor - changed crank sensor.
Defective Throttle Position Sensor - have not tested this.
Mechanical engine problems (i.e.—low compression, leaking head gasket(s), or valve problems - these have not been checked.

The order of steps you have taken to identify and fix the cause is the same as what I would do, and you have ruled out a lot of causes. Kind of surprising you have not nailed it already. :-\

Here is some of my personal experience with the remaining possible causes that may or may not be of use to you:

Throttle Position Sensor: When mine went bad, I got a specific trouble code for it. I believe I damaged it accidentally by spraying carb cleaner on it while cleaning the TBI (did not realize this part was still attached and sensitive to chemicals). According to the Haynes manual, a problem in any of the TPS circuits will set a code 21 or 22. Once a trouble code is set, the ECM will use an artificial default value for TPS and some vehicle performance will return. Unfortunately, no test procedure is provided.

Mass Airflow Sensor: My S10 has a MAP sensor, which I recently replaced (did not help engine run better). The only MAF sensor I've had trouble with was on an '87 Buick 3.8, and in that case, the ECM stored a trouble code specifically for it. I tried cleaning it, but it did not help, so replaced it, which fixed the problem.

At this point, if you can find a shop with the necessary diagnostic equipment that is actually willing to USE it, I would do that.