01 Blazer p0300 code

[61_FL_Apache]

I just so happened to have my 97 Tahoe in the driveway and it uses the same ICM so I swapped it and no change. I also had a spare coil and tried that too.. No change.

[76C10Stepside]

Originally Posted by 61_FL_Apache

I just so happened to have my 97 Tahoe in the driveway and it uses the same ICM so I swapped it and no change. I also had a spare coil and tried that too.. No change.

I assume you made sure the '97 Tahoe runs before trying the ignition module and coil from it, LOL.

Not sure why some of the electrodes on the distributor cap have corrosion while others do not, nor whether it means anything. Looks like your ignition system is fully electronic, though, based on the round electrodes. My S10 has a "hybrid" system that still uses a rotor to distribute the spark to each spark plug. Not sure how yours works.

Did you try clearing trouble codes from the ECM, then retesting to see if it is actually trigging the "0300" trouble code right now? Sometimes people forget to do that, so worth asking. I found this other page that DOES list the 0300 trouble code (https://repairpal.com/obd-ii-code-chart) that has this info about it: https://repairpal.com/obd-ii-code-p0300

What Does OBD-II Fault Code P0300 Mean?
OBD-II Code P0300 is defined as a Random, Multiple Misfire Detected

P0300 Symptoms

• Check Engine Light flashing
• Rough running, hesitation, and/or jerking when accelerating
• In most cases, there are no adverse conditions noticed by the driver
• In some cases, there may be performance problems, such as dying at stop signs or rough idling, hesitation, misfires or lack of power (especially during acceleration), and a decrease in fuel economy

Common Problems That Trigger the P0300
Worn out spark plugs, ignition wires, coil(s), distributor cap and rotor (when applicable)
Incorrect ignition timing
Vacuum leak(s)
Low or weak fuel pressure
Improperly functioning EGR system
Defective Mass Air Flow Sensor
Defective Crankshaft and/or Camshaft Sensor
Defective Throttle Position Sensor
Mechanical engine problems (i.e.—low compression, leaking head gasket(s), or valve problems

...so the trouble code does support your assertion that there is a misfire condition or even non-fire condition on some cylinders. It's a long list of possible causes. If the misfires always occur on the same cylinders, I should think it more likely that the ignition wires and/or spark plugs on those cylinders are suspect. On the other hand, if the misfiring is not always on the same cylinders, I'd look for a more central cause.