PrimerPLus
10+ Year Contributor
- 1,158
- 20
- Jul 28, 2011
-
Tokyo,
Asia
I am trying to diagnose a P0300 Random Misfire CEL.
Here is what I have done so far to try and solve / figure out the problem.
Had my FIC 1150s tested. All were checked by FIC and passed. No issues.
Replaced power transistor, coil pack, plug wires NGK, plugs (BPR7ES gapped .025" due to being told I was getting blowout at high rpm when at .028"), Cam Position Sensor, and Alternator to a Galant 90amp.
Not sure what else to check. I am pretty sure my o2 sensor is good as it cycles when watching a log in ECMLink.
I found a website that talks about EGR and that it can cause rough idle and random misfires if not working properly.
http://www.aa1car.com/library/egr.htm
I also have CELs for P0443 but I just disabled with ECMLink.
I am thinking about just doing a complete Emissions Delete if it is the EGR valve as I am pretty sure the evap system isn't working because I have this CEL that I still can't figure out the cause.
Any suggestions on what to check etc would be helpful.
I do have an EGR blockoff plate that I have not installed. Maybe I can install it and leave the EGR valve connected to the vacuum lines just for testing purposes to see if I get the code again?
I also can't help but wonder if the gap on my plugs are causing the misfire.
I see that others experience some sort of power loss or "limp mode" my car doesn't show any signs of that. I usually get the code when I am letting it warm up at idle or just get into the car and take off. If I clear it with ECMLink right then I won't see it again for a while maybe a day later.
It hasn't affected the driveability of the car but I know there is some reason for the CEL and would like to fix it.
Here is what I have done so far to try and solve / figure out the problem.
Had my FIC 1150s tested. All were checked by FIC and passed. No issues.
Replaced power transistor, coil pack, plug wires NGK, plugs (BPR7ES gapped .025" due to being told I was getting blowout at high rpm when at .028"), Cam Position Sensor, and Alternator to a Galant 90amp.
Not sure what else to check. I am pretty sure my o2 sensor is good as it cycles when watching a log in ECMLink.
I found a website that talks about EGR and that it can cause rough idle and random misfires if not working properly.
http://www.aa1car.com/library/egr.htm
I also have CELs for P0443 but I just disabled with ECMLink.
I am thinking about just doing a complete Emissions Delete if it is the EGR valve as I am pretty sure the evap system isn't working because I have this CEL that I still can't figure out the cause.
Any suggestions on what to check etc would be helpful.
I do have an EGR blockoff plate that I have not installed. Maybe I can install it and leave the EGR valve connected to the vacuum lines just for testing purposes to see if I get the code again?
I also can't help but wonder if the gap on my plugs are causing the misfire.
I see that others experience some sort of power loss or "limp mode" my car doesn't show any signs of that. I usually get the code when I am letting it warm up at idle or just get into the car and take off. If I clear it with ECMLink right then I won't see it again for a while maybe a day later.
It hasn't affected the driveability of the car but I know there is some reason for the CEL and would like to fix it.