Problem started when I installed KB 2.6 about a year ago. Car had slight misfire at idle.
Call KB they had no answer other than 4.6 Ford sometime do that.
Looked for vacum leaks, found none.
Changed plugs twice, two different heat ranges.
Changed plug gap on plugs three different times.
Reloaded the KB tune twice.
Took car to JMS put on dyno 453rwhp.
Changed out coils to MSD coils.
Took car to the dealer (gave me hassle about supercharger) charged me $200 to do relative compress check (OK) fuel system check (OK) ignition check (OK) and a few other things. They could not nail it down, dealer said they though it had sticky valves.
Took out old lash adjusters and installed new ones.
Took out all injectors, ultasonic cleaned and flow, reinstalled.
Car still has misfire at idle and very low rpms. But runs great once you stick your foot in it.
Two weeks ago I called KB back and they were very good to up date my tune at no charge and suggested that I use Brisk plugs gaped at .035
I installed tune and plugs and car still has the slight miss at idle only after the car warms up, no miss when engine is cold.
But the really strange thing is two days ago I took the car for a spin, and after it warmed up the slight miss appeared again. But when I turn the air conditioner on it goes away. With the a/c on it run and idles just fine.
I'm confessed why, should I just get a custom tune should that take care of it. In the past I have had Johnson Motor Sports (Monty) do tuning with great success.
Linear Mode
