I just posted about the cylinders filled with gas. Well the FPR o-ring wasn't sealing. I tore it down and reassembled it and fixed the leak. Now I have the original problem. I guess it wasn't the regulator.

Ok Senerio, 2000 4.3L blazer started running rough, throwing the P300 random missfire, I changed the FPR plugs. cap, rotor and wires. and it still seems to be firing on half the cylinders. What is left to check?

Fuel pump maybe, how can I be sure with just replacing random parts?

2 weekend used so far and its my kids car.

 

Did you try replacing the spark plugs yet? if there was gas in the cylinders than the plugs are now fouled out from gas

 

yes, did cap rotor and plugs after the flood, thanks though

 

Have you read through the rather large P0300 discussion post yet? --> The dreaded P0300 CAUTION LONG POST
Or through the diagnostic for P0300? --> P0300 Explained

 

yes,

I have read that write up, It is so long and goes over a lot of things I have tried already. This is were I got mosy of my ideas for the FPR. I did notice something an the top of the plenum, I pulled of the FPR sensor and it was a very loose fit. The gasket is chewed up a little. But, I pushed down on it to make a seal and it made no difference in the rough running. I tried to clean the port on the bottom of the sensor with no luck.

I never really noticed an actual fix. And when there was a fix, It was on something I had already tried.

After all the reading and fixing I have done, I can see why this code it the worst to trouble shoot. But thanks for all the advice, keep it coming until I fix this thing

 

Um... What did you push down on...? You cannot push down on the FPR with the engine running as it is inside the intake plenum... Could you take a picture of the items you are referring to, circling them in the picture so we can get the terminology correct?

Please go through everything that you have tried as well as the outcome. Be specific.

 

I pushed on the pressure sensor on the top of the intake. see the pics, It didn't do anything anyway, I swapped it with no improvement

[IMG]local://upfiles/10245/DD0AA3E5C2CB4FFEBE5727CF6C08A080.jpg[/IMG]

[IMG]local://upfiles/10245/AA7DCA8D76A5407C8C5EAD0B650FB37F.jpg[/IMG]

 

Ok, that is the MAP sensor. It can move around without loosing a seal.