P0300 random misfire

[Anusface69]

Today I replaced the CKP sensor. Test drove under the same conditions and had zero misfires. Gonna drive tomorrow to see how it goes, and get the last two readiness monitors ready. I will let you guys know what happens. I really do appreciate all the tips and input, I’m an Audi guy so it was nice to get some info from people who know

 

[Anusface69]

I knew it was too good to be true. Under light load started misfiring only on 6, when I got closer to the shop after about 5 miles misfiring on 6, it started misfiring only on 7. Ltft at idle:
Bank one 12%
Bank two 5%
At 2000 rpm
Bank one 16%
Bank two 14%
Stft at idle: both banks 0
At 2000 rpm
Both banks bouncing from 0 to 7
This misfire seems to happen when I start the truck cold, after driving for 5-10 minutes. Engine warmed up. Yesterday when I let it warm up first no issues. I did smoke test again and made sure I had decent pressure with the smoke so I could just rule out the intake gaskets.

 

[Anusface69]

It’s too bad I can’t post a video of the data stream on here.

 

[Fless]

It’s too bad I can’t post a video of the data stream on here.

You can post it on YouTube or another hosting site and post the link here.

 

[MassHoe04]

I had misfires on an 05 4.0L Jeep. Was actually fuel related.
It kept happening until my fuel pump completed died one day.

I would suggest checking fuel pressure before, during and after start-up and warm-up to see what you have going on.

A gauge can get loaned out from your parts stores with refundable deposit, so checking fuel pressure on your system will cost nothing other than a few minutes of your time.

I would at least want to rue out the fuel pump as a possible cause.

 

[Anusface69]

I have a confirmed fix. Replaced cheap ignition coils with Delphi and the truck is fine. Can I ask questions about the hydra boost here or should I start a new thread?

 

[mattbta]

New thread, please.

 

[Rocket Man]

These trucks don’t like cheap aftermarket parts like coils and sensors. Glad you figured it out.