Weird P0300 code
Thread Starter
Pro
Joined: Oct 2009
Posts: 712
Likes: 0
From: Panama City Beach Florida
Weird P0300 code
So my car keeps throwing P0300 code after I put the forged motor in. The only difference in my car from when it ran before is that its now a forged 347 and not a stock 346, and I deleted the air/egr system and blocked off the ports on the exhaust manifold.
So it keeps throwing this code, but it runs like a champ. Its definitely not lost any power however I do notice at idle the rpm will fluctuate about 50-100 rpms a little.
I do think I may be running rich because the car is tuned for 42 lb injectors which I still have in the car, but its also tuned for a procharger, which is no longer on my car. I have brand new NGK TR6 plugs in and brand new 10.4mm wires.
Again, the car seems to run well except for that little 50-100 fluctuation at idle.
So it keeps throwing this code, but it runs like a champ. Its definitely not lost any power however I do notice at idle the rpm will fluctuate about 50-100 rpms a little.
I do think I may be running rich because the car is tuned for 42 lb injectors which I still have in the car, but its also tuned for a procharger, which is no longer on my car. I have brand new NGK TR6 plugs in and brand new 10.4mm wires.
Again, the car seems to run well except for that little 50-100 fluctuation at idle.
Drifting
Joined: Jul 2005
Posts: 1,484
Likes: 27
From: Torrance Calif
Took me a year to figure out that one, but it ended up being the valve timing. 
There are ways to shut off the algorithm that looks at the acceleration between cylinder firings that throws this code.
There are ways to shut off the algorithm that looks at the acceleration between cylinder firings that throws this code.
Team Owner
Joined: Jan 2006
Posts: 20,800
Likes: 59
From: Tellico Village, Tn
St. Jude Donor '08
So my car keeps throwing P0300 code after I put the forged motor in. The only difference in my car from when it ran before is that its now a forged 347 and not a stock 346, and I deleted the air/egr system and blocked off the ports on the exhaust manifold.
So it keeps throwing this code, but it runs like a champ. Its definitely not lost any power however I do notice at idle the rpm will fluctuate about 50-100 rpms a little.
I do think I may be running rich because the car is tuned for 42 lb injectors which I still have in the car, but its also tuned for a procharger, which is no longer on my car. I have brand new NGK TR6 plugs in and brand new 10.4mm wires.
Again, the car seems to run well except for that little 50-100 fluctuation at idle.
So it keeps throwing this code, but it runs like a champ. Its definitely not lost any power however I do notice at idle the rpm will fluctuate about 50-100 rpms a little.
I do think I may be running rich because the car is tuned for 42 lb injectors which I still have in the car, but its also tuned for a procharger, which is no longer on my car. I have brand new NGK TR6 plugs in and brand new 10.4mm wires.
Again, the car seems to run well except for that little 50-100 fluctuation at idle.
Pro
Joined: Aug 2010
Posts: 545
Likes: 4
From: Calgary Alberta
From the service manual:
"Conditions for Setting the DTC
The PCM is detecting a crankshaft rotation speed variation indicating a misfire sufficient to cause emission levels to exceed mandated standards."
I suspect your wandering idle is to blame. When the car was tuned you had the additional mechanical load of the supercharger to account for. This coupled with over sized injectors is in all likely hood making it tough to achieve a steady idle.
Back to stock injector sizes and retune.
"Conditions for Setting the DTC
The PCM is detecting a crankshaft rotation speed variation indicating a misfire sufficient to cause emission levels to exceed mandated standards."
I suspect your wandering idle is to blame. When the car was tuned you had the additional mechanical load of the supercharger to account for. This coupled with over sized injectors is in all likely hood making it tough to achieve a steady idle.
Back to stock injector sizes and retune.
Drifting
Joined: Jul 2005
Posts: 1,484
Likes: 27
From: Torrance Calif
Thread Starter
Pro
Joined: Oct 2009
Posts: 712
Likes: 0
From: Panama City Beach Florida
Hmm, I hope its just that the car was tuned for the charger, and now has no charger. Not to mention I now have 6.0 heads with larger valves than stock, and a completely different compression ratio.
I sure hope thats the issue.
I sure hope thats the issue.
Pro
Joined: Aug 2010
Posts: 545
Likes: 4
From: Calgary Alberta
Unlikely that just mechanical changes, compression-cam-heads etc., would be enough to require larger injectors. So tune and stock injectors might be the route to go. Try tuning first I suppose. Not sure if the relearn for the crank sensor is valid for these cars but it wouldn't hurt to try.
