Idle fluctuates. IAC or something else?

[RockinRobin]

Well I adjusted the IAC Position until it was right around 10% at idle and adjusted fuel lb/hr at idle until I got a range it liked and everything was smooth. But after cooling it off for a little while, now when I start it up the idle fluctuates quite a bit. What should I adjust to smooth it out? Did I go to low on idle fuel? Throttle plates open/closed too far?
Racing only application, high compression big cam engine that has run down the track well, just trying to clean up the idle. No, I'm not going to lower the idle from 1600. If you're a footbraker you understand why. Sniper 4500. Can't let Sniper self-tune idle, it's complicated as to why.

[AndyF]

Enrich it up a little. You'll most likely need to add fuel for cold starts and maybe raise the idle speed when the engine is cold.

[RockinRobin]

Thanks, that did the trick! It seems to like around 10.4 lbs/hr to idle. Still fluctuates slightly. IAC Position is a little low, from 1 to 4%. I guess now that I have the fuel where it likes I need to tweak that. (the IAC)

[Danny Cabral]

https://forums.holley.com/showthread...e-Tuning-Notes (EFI Idle Tuning Notes)

[RockinRobin]

https://forums.holley.com/showthread...e-Tuning-Notes (EFI Idle Tuning Notes)

Good info. Thanks Danny!

[AndyF]

I have race engines that can be started in cold weather by just hitting the start button. A Sniper will not do that out of the box, but you can dial the cold start performance on a race engine. The trick is to find the "happy spot" at hot idle first. Once you find that spot then you can work on hot starts, cold starts, etc.

[RockinRobin]

Mine will start cold with just the starter button, and starts very quickly when warm. Getting very close, but it looks like a cold front is going to keep me away from the track for another week. ::-(

[AndyF]

Yes, starting is a combination of IAC Parked Position as well as Cranking Fuel and Fuel Prime Percent. Cold run after starting is dependent on the Temperature Enrichment settings. It isn't too hard to figure all of this out, you just have to be organized and methodical about it. Work on one problem at a time and use the Datalogger to tell you where you're at.