Holley Sniper: dramatic fuel enrichment when exiting CLC

I'm just now starting to understand how the sniper EFI works and how to adjust things to fit my engines wants, but I'm not sure how to move forward on this issue.

Only been driving the truck around town for a while now. Relatively low load on the engine. never really getting above 50mph and it's been cruising fine. When I took it up on the highway it highlighted what I think is an AFR compensation issue. If I'm laying on the throttle and remove my foot the EFI exits Closed Loop, IAC hits and maintains 20%, and AFR drops dramatically (9.6-11.5 depending) despite the target being somewhere around 13. The higher the RPM the more dramatic the drop. I initially thought it was poor CLC settings, but CLC% is 0 since it exits CLC.

EFI folk, please advise.
Thanks.

Holly CL/Learn only works when there isn't a modifier active. Any rapid throttle position change activates the tps roc (rate of change/how fast the throttle moves) table which kicks it out of closed loop. Cold starts are another modifier table that will keep you out of learn as well.

Going rich or lean on deceleration (what your describing here) isn't uncommon, you can make it less drastic of a change but you'll have to MANUALLY tune that.

The IAC at 20% is a hold position while you are driving so that the IAC can catch an maintain the idle when you remove your foot from the throttle and come to a stop. This is also a table you can adjust which includes the IAC hold percentage, the rpm above idle at which it starts it's ramp down and the time of that ramp down. If your truck is an automatic you can probably leave that alone, it's usually only an issue on manual trans vehicles. But if it doesn't hit that rpm level to start the ramp down it can cause a "hanging" high idle.

The self learning features of all efi systems are related only to the base fuel table at steady state or low tps roc. This is my main gripe with how they are marketed as it causes people to think they shouldn't have to adjust anything manually, which couldn't be farther from the truth.

I think this is the little piece of info that fits it all together. I've been manually messing around with settings without paying any mind to TPS ROC. Thank you sir!

It's very easy to get obsessed with micro tuning EFI. I got to the point that if it runs good, I won't even bother turning the display on. Like bluex said, the fact that the aftermarket advertise these as " self- learning" is a fraud. They are complicated and until you fully understand how they work they can be frustrating. I have nothing bad to say about Sniper

youd notice on a lot of OBD2 vehicles that sudden dropping off the throttle will put the vehicle in open loop, a big part of that is staying in closed loop, with a dramatic drop in throttled air, then a delay in which a IAC steps in to control the idle air, and the drop in load on the engine.. basically staying in closed loop will just cause driveability issues because its going to over or undo do any change , and its not the steady state behavior the vehicle is doing most of the time.

If you were to drop most of the pedal, but still have some throttle opening, like the minimum, would you see the same thing?

If not, carry on, its just how sniper's programmed

If your dropping throttle from WOT, even if you still had some throttle, you should expect to see open loop. this is to ensure its not leaning out too far

Ya alot of this is people also don't realize factory efi can do the same thing, you just don't see it because there's not a display with flashing colored numbers in your face lol.

bluex said:

Ya alot of this is people also don't realize factory efi can do the same thing, you just don't see it because there's not a display with flashing colored numbers in your face lol.

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If you have a OBD1 GM you can , while running, short A and B on the ALDL and then the service engine soon lamp will actually do that, quite literally flashing! Just drive around and it will keep telling you exactly what loop youre in