This morning my wife calls me that the Service Engine light came on. 1999 Blazer LS 2wd 4.3 motor. Went to go pick it up and notice that the accelerator would kinda hesitate a little, when I first press down on it. Last week I did a full tune up. replaced belt,dis. cap, rotor, wires , and ac delco plugs. Also replaced PCV valve and fuel/air filters. I checked the wires and I am getting good ohms.
I know that the P0300 has something to do with random misfire. Is there something I can do to check the cap and rotor? or is this something else? Also I have noticed that the muffler leaks from the begging of the last piece of pipe and out of the exhaust. It is cold out about 50f. I double checked the Plugs and notice that #3 was loose because its hard to replaced. Found out you can turn the wheel and lower the plastic cover on the column. Tightened it up and the code still remains. I just bought the truck 2 weeks ago. Any info will help, I am going to take it to my mechanic tomorrow or Monday. Thanks
ANthony

 

Have you read here yet? It explains the code. You are correct, it's a misfire.

 

You could also search for P0300 and read up on it. The thread linked to below runs through about every angle in terms of diagnosing this code:
The dreaded P0300 CAUTION LONG POST

 

Where would the H02s be? I have checked wires and plugs.

THanks

Anthony

 

In the exhaust pipe... Search will shed more light.

 

Thanks for the illustration, THats for a 98 right does it work for 99?
THanks Again

ANthony

 

98+ are the same.

 

Change the rotor cap