Help correcting a surging idle

[Cope]

Friend of mine fired up his new combo this week and the idle surges very bad. (FAST)

Where do i start to fix the idle problems. The car runs good under throttle.
Any info would be much appreciated..

FAST,NA,4.6 mod motor,


thanks

Cope

 

[HighPSI]

Two places I would look at first: 1)Is it idling too lean? Try raising the VE numbers at idle. Also, try idling it in open loop and see if it goes away. 2) You need to check the IAC gains, in the idle parameters section. Make sure they aren't over correcting.

 

[bobc455]

Maybe also too much timing at idle?

I would try lowering your A/F ratio instead of raising your VE values, especially if you are in open loop.

-Bob Cunningham

 

[NoSlix]

Yo, Cope! Whatsa happening? An idle surge will be three things......a/f ratio, ve and/or timing. What's the timing like around where it idles? What af ratio? I find that I have to idle most stuff fairly rich....say 12.5:1. It's trial and error. Try changing the af lower at the idle spots and see what happens. If you've got a lot of timing at idle....say 30+ degrees, lowering the timing at that point will richen up the mixture so you may have to go back and forth a few times to nail it down.

 

[236rocket]

this may sound stupid but check alt output/batt voltage i got me once!-good luck