[jdlatil]

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.

[BKid]

Maybe a boost a pump would help.

[stlwagon]

Have you datalogged to see what your MAF counts are? Probably time for a dyno tune!

[PLstang]

I concur, time for a dyno tune.

(Brisk plugs.....Ugh)

You should have a BAP with the KB already so that can't be the problem, besides it's at idle not WOT.

Miss only starts when it's warmed up not when it's cold, if the miss was when it was cold I'd say not enough heat in the motor or maybe you need a boos-a-spark.....you're not igniting the fuel. I take it you're just running normal super unleaded, nothing special (mine has problems until it get's heat in the motor when I run C23).

You got me, I'd go with a dyno tune and do a little data logging as was mentioned.

[travelers]

+2 on the dyno and datalog. That can tell you a lot.

[mineralgrey]

Hey neighbor. I'm 50 miles from you. The problem may be in the mass air meter. I had the same set up and JMS made a new housing and it solved the problem. I still have some issues at idle but I still need to have them tune the car again. I'm having clutch issues.

[jdlatil]

Thanks for all the input:
I have one of the basic Excalibator SCT box w/no LCD screen.
Before sending the SCT back to KB I was getting a P0308 cylinder #8 misfire and P0300 random misfire code.
Took car out for another test run tonight about 15 miles of stop and go. Weather was different, No miss and got home and checked codes there were none.
That's great, if I let car idle for a few mintues I can hear the very slightest of a miss occasionly. I don't know if the car's cpu has learned to take care of it or the weather change was enough to make it run different.
I happy with the way it runs now, 100% better than before sending off SCT to KB.
Thanks for everyone's input. Yes, it was in the tune.
IT'S HAMMER TIME!
My birthday is coming up some, may be I will give may self a SF3 SCT programmer and a custom tune at JMS. Unless you think there is a better programmer?

[travelers]

Originally Posted by jdlatil

IMy birthday is coming up some, may be I will give may self a SF3 SCT programmer and a custom tune at JMS. Unless you think there is a better programmer?

That would be a good idea. They can do a datalog on the dyno and see what's going on.