actionexpress

I have 00 gt that I put a KB supercharged engine in about year ago.The engine has about 1200 miles on it. It has ran great at some HPDE events until recently. The engine has developed a miss. It pops out the exhaust with engine around 2-3000 rpm every now and then- not constantly.It does it whether the engine is hot or cold. By taking off the COP wire, I have found it to be the #5 cylinder. Here is what I have done so far-
Using a scan tool, I found no codes, but have seen the cylinder has a miss.
Leak down on the cylinder-12%
Compression test on cylinder #5 and #6- both 160-170 lbs
Installed new COP, injector, and spark plug
Used a timing light and timing was not erratic
Checked the valve spring and it looked fine

I am at a lose as to what it could be. Any help or suggestions would be greatly appreciated.

uberstang1

What kind of exhaust are you running? Does it have cats? The pop could be due to the lack of backpressure. It could also make a pop out the back if the car is running rich due to the tune. This may not be an actualy engine miss.

actionexpress

The car has long tube headers with cats.
The miss is not due to running rich, we had checked for that.
We had checked the engine with a scan tool and it shaws a miss in #5 cylinder. But from what, we cannot find.
We also had check for a vacuum leak on that cylinder.

cisurfer

is the cop getting power, test the harness plug

actionexpress

We checked the COP for power

uberstang1

I assume if you have a CEL from cyl 5 you changed the plug and check the compression right?

actionexpress

Yes we changed the plug and checked compression- compression was fine.
No CEL. But it can be picked up with a scan tool.The engine just pops out the exhaust every few seconds.