Why do I keep getting P0300 misfire code?
Thread Starter
Joined: Jun 2004
Posts: 5,125
Likes: 4
From: Alexandria, VA
Why do I keep getting P0300 misfire code? I just put new heads on the car and got it tuned. I'm running 11.6:1 SCR and around 8.0:1 DCR now. Everything was running great, except for it was getting a few degrees of KR from 3-5k for no apparent reason. As for now, that's a separate problem (or is it?). I drove the car home and it died on the way. It turns out the walbro fuel pump took a **** and wouldn't hold pressure at idle after about 45 min of driving. I cleared the PCM and let it sit overnight and drove it the next day and it was fine (except for the fact that the fuel pump would start acting up after a while). Next thing I know, it throws a misfire code. I keep clearing it until I take it back to the shop. We replace the fuel pump and clear the code again, thinking it should go away. Well, it keeps coming back. I've run some injector cleaner through it in case something was clogging one up but it has done nothing. I'm just wondering what the hell is causing it. I can't seem to figure it out. I'm gonna replace the fuel filter pretty soon but want some ideas on what else it could possibly be.
TECH Fanatic
Joined: Aug 2005
Posts: 1,691
Likes: 1
From: Sunny London, UK
I understand some cams can cause that. You can tune the misfire code triggers, there are heaps of tables and values that manage it. Take a look. Maybe do a search too, should be some info on it somewhere.
Thread Starter
Joined: Jun 2004
Posts: 5,125
Likes: 4
From: Alexandria, VA
It's not a ground issue, I'm pretty sure of that. I guess I'll just have my tuner take a look at it again if there's nothing else that could be causing it.
Funny...I'm having the same issues. Had heads put on about two months ago and have had P0300 come up a couple of times. Car seems to run fine though.
As was mentioned earlier, aftermarket cams can trigger this code, especially the more aggressive the cam is. In my case I have had a mild cam (TR220) in my car for a couple of years without this problem. Now P0300 decides to show up?
As was mentioned earlier, aftermarket cams can trigger this code, especially the more aggressive the cam is. In my case I have had a mild cam (TR220) in my car for a couple of years without this problem. Now P0300 decides to show up?
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Thread Starter
Joined: Jun 2004
Posts: 5,125
Likes: 4
From: Alexandria, VA
Nope, no updates yet. I still have yet to get back to my tuner's place to have him check it out. On another note, my battery voltage drops to around 9-10 if sitting at idle for a while. I checked all the connections to alt and battery, disconnected, reconnected, and tightened my battery connections as well as the wire on the back of the alt. No dice.
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