Jump to content

Sign in to follow this  
cheerdude63

Random Misfire P0300

Recommended Posts

Hello all, I am new to the site so if this is in the wrong place let me know.  I have a 2015 GMC Sierra, I used the torque pro app to confirm that cylinders 1-4 are recording a misfire under load.  It doesn't miss at idle or at cruise speeds.  Is there something that links all 4 of these cylinders together in the engine harness, like a common ground or something like that.   One more thing, I don't think it matters but, the engine is supercharged with a Magnuson TVS 1900, it has also had the DOD deleted out of the ECM.  Any help would be awesome, thanks.  

Share this post


Link to post
Share on other sites

If only misfires under load I would start with looking at the plugs and wires. If it was a wire or ground issue it should be misfiring all the time,  not just under load.. 

1-3-5-7 are driver's side

2-4-6-8  passenger side. 

If you have 1-4 like you said, then those would be the front two on each side. 

Share this post


Link to post
Share on other sites

Oh where to start. I would swap spark plugs and wires out. There should be a Ngk colder plug in there and at least ac delco performance red wires. Then I would remove intake and check for debris. Those kits allow blow by back to intake. 

What catch can do you have? I ask because next question is o2 and afr. But without a data log of a run hard to just pick the issue. 

Share this post


Link to post
Share on other sites
3 hours ago, Hillwood said:

If only misfires under load I would start with looking at the plugs and wires. If it was a wire or ground issue it should be misfiring all the time,  not just under load.. 

1-3-5-7 are driver's side

2-4-6-8  passenger side. 

If you have 1-4 like you said, then those would be the front two on each side. 

The scan tool I have is only picking up 1-4 or yes the front 4 cylinders. I can, with some certainty, move on a from a common ground issue then.  It is only under load. Thanks.

1 hour ago, 1SLOW1500 said:

Oh where to start. I would swap spark plugs and wires out. There should be a Ngk colder plug in there and at least ac delco performance red wires. Then I would remove intake and check for debris. Those kits allow blow by back to intake. 

What catch can do you have? I ask because next question is o2 and afr. But without a data log of a run hard to just pick the issue. 

I will be doing what you suggest today.  I am not sure what plugs are in it.  I just got the truck and have put just over 1000 miles on it.  The supercharger was installed by Davenport Motorsports in Calgary, AB. I know it does have MSD wires on it.  With all this info you guys have given me,  I am relived that is not mechanical, that was my assumption.  Now I just got to go figure it out, thanks. 

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

Sign in to follow this  

×

Important Information

By using this site, you agree to our Terms of Use.