I had my short block swapped a few months back. My original block had the loose spark plug problem and it damaged the threads of the plug well.

The car is Comptech SC with AC and 7psi pulley.

Well, recently I have been getting the "intermittent misfire" codes: p1399 followed by the p0301, 2, 3, 4.

I have spare coilpacks and that doesn't make a difference.
I have a spare MAP sensor and that doesn't make a difference.

It's really only under load. If I free rev, no CELs.
If I turn the wheel and accelerate hard, I get the CELs.
If I rev high and clutch dump (it's snowy here so no damage), I get the CELs.
Even before the CELs, it feels sluggish.

I pulled the injectors and they look clean.
I know that they could still be the problem. And that usually the injectors are the problem with these CELs.

HOWEVER: when pulling the injectors I found that the knock sensor was broken. It hasn't thrown a knock sensor CEL, but I know that it functions as a microphone. And I know there has historically been cross-talk due to superchargers. So by having the plastic shell breached, is the microphone now "super sensitive" and picking up the SC and retarding timing? Maybe the retarded timing leads to the p1399s? Or maybe they're unrelated and I have to replace the knock sensor and the injectors anyway....



Just a post for the archives.

Any thoughts?

 

Misfires are determined by CKP fluctuation. Ignition timing doesn't come into play, as the PCM already knows what the timing command is.

You'll still need to fix the broken knock sensor.


The P1399 is a temp DTC. You'll need to let it code 2X to get the specific cylinder #.

 

It goes to p0301,02,03,04. So all cylinders.

I have injectors and a knock sensor on order.

Unfortunately, I was fooling around with my current injectors and didn't oil the o-rings on reinstall...

Now my garage smells like gasoline.