1997 P0300 after intake manifold gasket replaced
 

Got a 1997 2WD 4.3L Blazer and discovered that it was leaking coolant at the intake manifold gasket. We tore it apart today and replaced the gasket and the put it back together. Started it once before putting everything back just to make sure it would.

Once we got everything on we started it again. Only getting one code P0300 random misfire. At first it was idoling really rough. We adjusted the distributor and tried again. Code came back (we cleared it). We put on new distributor cap and problem persisted. Changed spark plugs code comes back. Saw some people saying that a wore gearing on the distributor could be the cause. Purchased a new remanufactured distributor and tried again. Code comes back. All new distributor parts and spark plugs and were still stuck.

It is still idling rough but not as bad as it was before replacing the distributor. The code normally doesn't come on until i rev the engine up to around 2000 RPMs.

Anyone got any ideas to check? Don't want to keep throwing money at this problem.

Also saw some people said ERG valve could be the cause. Pulled it off and made sure the connections were clean. The little rubber valve seemed to be working ok too.

Dont start throwing parts at it. Go back to what you just did. Something was probably installed incorrectly. Did you properly RTV the manifold sealing area? Did you take the time to clean out the valley and the combustion chambers? Did you inspect the condition of the injection system? Are you sure you routed all the ignition wires to the correct plug?

P0300 does sound like an ignition system issue more than anything. But it could still be your fuel system. Double check the fuel lines going into the manifold.

Hey thanks for the reply. We went through all the problem solving steps. Made sure the distributor was ok. Pulled the ERG valve and made sure it wasn't stuck open/closed. It drove us insane. I gave and took it over to the dealer. $650 later and I got a new fuel injector unit installed from the dealer and it is running like it self again. Actually getting better oil pressure right now then I was before, probably because there isn't a leak in the lower intake manifold anymore.

Don't give me a hard time about taking it to the dealer. I was already going to have to pay them $96 for the diag and then the part was going to be $350 from them. So I thought just pay the $200 more and get it done with. Hopefully this beast doesn't give me any other problems soon. I need to check out my bearings though since they are making a grinding noise at slow speeds.