P300, P301, P303, P306 Codes.. Random misfires

You may have it figured out mark,the only other thing would be ,crank sensor,or distributor.

This could be caused by a bad dist. cap and/or wires or spark plugs.I change plugs when this happens because it's the cheapest solution.If the plugs show spark they can still be bad.Then I test the wires to ground and if there's spark,my next step is to remove the upper intake.Leave spider injector hooked up.Disconnect all electrical supply to the distributor, and coil wire too, and pull all poppet nozzles from heads.Put paint can caps under all six poppet nozzle injectors.You can have someone turn vehicle over and watch for fuel to fill caps.It will show immediately if injectors are filing with fuel. My guess is it's the injectors.A pressure regulator is a long shot. If you have a manual shift veh. make sure it's in neutral and parking brake is on.I have purchased injector sets from ebay and rebuilt with known working injectors to replace bad ones.

A fuel pressure gauge does help to determine fuel pressure after pressurized and when key is off. For 60 bucks, It is a good investment.I.M.O. Good luck.

Harbor Freight has a fuel pressure tester on sale right now for $20.00. Go to: http://www.harborfreight.com/automotive-motorcycle/diagnostics/fuel- injection-pump-tester-92699.html

Thanks guys, I appreciate the input. I'm moving forward with the project this week. Hope this works..

Good news! I replaced the fuel spider with the newer designed injectors and the truck runs great! no misfires. Cleared the codes and nothing came back. Only other things I replaced were a new PCV valve and gaskets. Runs like new! Fantastic!

I have a 2002 chevy blazer. Changed the spider gear and spark plugs. Now my check engine light is flashing. She hesitates at first with a miss. Then smooths out. What can be the problem?