Prostangmods

I have a 2001 with a keene bell making 12psi. Since I installed the kit I have a misfire that you can here at idle but goes away under high load and then comes back at 5000rpm. I have changed plugs, coilpacks, crank sensor, cam sensor, fuel injectors, everything. The car makes 12.8 psi with the 12psi pulley so I don't think its a vacuum leak. Please if anyone has any suggestions help me out. Thanks!!

Prostangmods

I have also had it dyno tuned and the a/f ratio, timing, and fuel pressure are all with in spec. Thanks

hotrodV8

have you done any internal work on the motor

Prostangmods

yeah, I did a compression ck everything is fine.........

n/a_threat

Well I was gonna mention to check compression on that cylinder, but you did it already.

Let me offer some other potential reasons for a misfire:

a leaking/damaged intake gasket leaking unmetered air into that chamber

exhaust valve may be hanging open slightly

a slightly recessed/sunken valve for that cylinder

hotrodV8

ok well i'm gonna kinda give you a list of the stuff that usually comes along with anything over 10 psi, you need a new chip, fuelpump, bigger injectors, mass air flow unit and a new tune, and probably some upper engine work to keep everthing from detonating on you. so not sure what all you have done to it but you cant just slap a supercharger on a car and go.

Prostangmods

Here is a list of mods on the car, SCT chip and dyno tune, keene bell boost a pump and in line pump, 42 psi injectors, SCT big air mass meter (tuned to the injectors) 2 step colder plugs from ngk, centerforce clutch and flywheel, mac hig flow hpipe with cats, 373 gears, mac upper and lower control arms, wideband a/f guage, 75 mm throttle body, intercooled keene bell 1.7 ltr kit. I know a great deal about tuning and superchargers so I know you don't just bolt and go. No boost was even closed to applied to the car until it was tuned on a mustang dynometer by guys who tune stangs all day long.

bluepony4.6

Add to this bad or damaged plugs, plug boots or coils

Antifreeze or water leaked into spark plug hole causing an arc (happened to me).

Prostangmods

Problems fixed, it was a vacuum line to the EGR vacuum control valve. Thanks for all the replys.

Dan04COBRA

Nice, do you have your factory short block, internals and all?