Code p0300 after replacing thermostat

That is a random misfire, you might have got something wet. Are there any driveability issues? Why were you checking codes, any particular reason?

It will barely go down the street. I did not check the code until the engine light came on.

Did you have the light before you worked on it? How long since a tuneup? Use a gauge and check fuel pressure. Plugs--plug wires, distributor cap and rotor all okay?

I changed the plugs and wires and it ran okay for about a day then back to the same thing.

How about the fuel pressure? Some of the national brand autostores used to loan out a fuel pressure gage. Do you have the spider fuel system on this? They are noted for problems.

I am not really sure. Is there a way to tell?

The Napa parts book shows you have the spider fuel system.

Okay, I will not be able to do anything until Monday. Thanks for your time.

No problem, have a good evening.

I am having the p0300 code too. Engine starts and runs great. 2003 s10 4.3 I have changed about every part except the ICM and spider injector. Soon as I get a fuel pressure tester I will check that. On my obd2 reader it shows ignition advance at 17 degrees idle and 45 degrees driving.

I have seen the spider injector, weak fuel pump and the MAF sensor cause this code. Do not worry about the timing that sounds normal. Here is how you can check the fuel pump:

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

(55-62 psi)

Please run down this guide and report back.

Cheers, Ken