2003 s-10 Code P0303

well, your plugs and filter are due......

Is there any arcing when looking at the engine bay in darkness (engine running obviously). It could be as simple as a bad coil or wire shorting to the block, etc. You may want to try swapping two wires to see if the problem moves to another cylinder. How does the fuel pressure test at the rail??

Thanks, Andrew.

Sounds like you have a sticky poppet valve on #3. Try running a can of SeaFoam cleaner through it. You might also want to run a pressure test on the fuel system. You will see the pressure drop fast with the key off if the injector is leaking down.

Steve,

Did GM still use that poppet design in 2003? I don't feel so bad for my 95 now if that's the case. It seems like the design needlessly overpressurized the fuel system to open to the poppet style injector. I thought they moved away to actual injectors but I've learned that you certainly know your stuff when it comes to these motors.

Thanks, Andrew.

They used a remote injector with a poppet valve on the intake end. Not the spider style CPI like the earlier engines. Basically you have 4 versions of 4.3 in use. First they were carbed, next came the TBI, then the early style CPI, then the later style SCPI. The last version used an independent firing injector (basically an electronic version of a poppet valve) but was still fed from a central regulator block. There are kits that allow you to convert the earlier units to the latest design.

Thanks Steve, The weather has been bad here, and I have not been able to get out and work on it. I put some Chervon Techron or whatever they call it. but it does not help..Ill try the seafoam. It just seems as though its an injector.

Is the pressure tap the same size as a tire valve? I had a 93 blazer, but I don't remember the size, at the time. Thanks again, Steve

Not the same size valve. You can probably borrow the proper gauge from auto zone or advance.