Learning to Tune the Holley Sniper

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Originally Posted by Caddy Dad

I just got my Mk IV with BPE 347 Holly Sniper EFI out on the road this week. She's running great. Not much popping etc when I coast down a hill. However, I do have a an issue where the RPM will almost drop to zero and then recover when I push the clutch in when coasting up to a stop. This seems to be a common occurrence with Snipers and there are multiple threads on the Holly Forum for me to research, but just wondering if you also ran into this issue? If so, how did you solve it?
Thanks!

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I had this exact problem. I now have my desired idle speed set at 800 and set the IAC exactly according to Dave/Holley's instructions. My issue was that the IAC was set too closed and I needed to open it up a smidge. Make sure that you fiddle with it set up the way to plan to drive on the street. What messed me up was that I originally set it up without the air cleaner on. After putting the air cleaner on, a slight restriction was added and the throttle blades needed to be opened just a little to compensate. I have 3700 miles now and it runs great. I am a big fan of the Sniper. From sea level to 11,000 feet on a cold morning, the car starts right up and drives great. I average 17-19 mpg and even got 21 on an extended drive at 65 once on my 347.

Id like to see this as a major subforum under the root. Great information here. I just recently installed the Stealth Sniper on my 383 Chevy Stroker. I also installed the Hyperspark Distributor and control box. I had a rough start as the initial setup was off. I went to pull the Sniper System off the car and decided to take it through setup again and there were several errors in the initial tune. Once setup, the self learning took over and the system performs flawlessly. After a few weeks we dyno'd the car and picked up nearly 80 whp over the Holley self learned tune. Additionally we picked up nearly 40% more gas mileage and the operating temperature of the car dropped 5-10 degrees. Currently working on setting the two step up.

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Originally Posted by Papa

I'd recommend first simply running through the quick setup for setting the idle and see where that gets you. I'd target ~900rpm to start.

IDLE SETTING/THROTTLE PLATE SETTING
Once the engine is up to operating temperature (above 160° F), the idle speed can be set to what was configured in the Wizard.
To do this, open up the Initial Startup gauge screen. With the vehicle in neutral, adjust the idle screw until the IAC Position
reads between 2% and 10%. While adjusting the throttle plate screw, watch the TPS value and make sure it stays at 0%. While
adjusting the throttle plate screw, the TPS position may begin to read higher than 0%. If this happens cycling the ignition switch
will recalibrate the TPS back to zero.
NOTE: Do not attempt to set the target idle speed and IAC position until the engine is above 160°F!

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Hi Papa,
I was finally able to get around to adjusting the IAC as you have described. I first checked the idle setting via the handheld. It was set to 800 so I bumped it up to 900 and enabled it by cycling the ignition. I started her up and let her warm up and go through a couple of cycles of the turning the cooling fan on (190) and off (180). The handheld was indicating the IAC was at 9 and TPS 0. So I adjusted it anyway up and down to get the IAC close to 6. I found out it doesn't take much, maybe a 1/4 to 1/2 of a turn to go from 2 to 10 on the IAC. The TPS bumped up to 1 so I cycled the ignition again to reset it to 0. I then took her for an initial test drive and it's much better, but not perfect. The RPMs will drop when I coast to a stop but not as low as before. Should I increase or decrease the IAC? I'm guessing decrease it to 2-4 and try again?

What about idle ramp down? I'm guessing that's its best to get IAC dialed in first then worry about idle ramp down?

Thanks for all your help!

Here are my IAC settings:

https://thefactoryfiveforum.com/atta...1&d=1604356031

I haven't modified them at all from the base tune. The only time my car has acted like it wanted to die was during a fairly abrupt stop where I basically clutched and mashed on the brake pedal to stop at a light. I typically have the RPMs down pretty low as I bring the car to a stop and don't have any issues.

Here are a couple of threads on the issue over on the Sniper forums:

https://forums.holley.com/showthread...dershoot/page2
https://forums.holley.com/showthread...wing-to-a-stop

This stood out to me from the second thread:

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Ensure the idle speed screw on throttle body, is adjusted to achieve an IAC Position of about 5% at hot idle.
In the Idle ICF, the "Target Idle Speed (RPM)" must be programmed to the desired RPM speed at hot idle.
Ensure the fuel injectors or spark plug wires (or any other high voltage wiring) aren't too close to the IAC motor/wiring.
The IAC motor is easily susceptible to electrical interference, and it'll cause strange occurrences and become inoperable.

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Dave

Some useful links from Holley:

Software: https://documents.holley.com/techlib...7installer.zip

How-To Videos: https://www.holley.com/support/fuel_...on/sniper_efi/

Sniper Forum: https://forums.holley.com/forumdispl...?82-Sniper-EFI

Very helpful thread!

I have some input from my experience and a question about spark plugs.

My experience,
I have a 427w from Forte with a Terminator EFI. I have always had an issue at low speeds with rough running and bucking as well as a rich smell at idle. I replaced the intake with a lower RPM intake and that helped a bit but it did not solve the issue. Also, I recently replaced the handheld as it had faded and they no longer support that version. During this process, I also upgraded all of the firmware on the Terminator ECU and reset the baseline to see if I could start from scratch and get better results.

After struggling with the base learning and before I started to begin the process of following the steps in this thread, I thought I would address the spark plugs. I was afraid they might be suffering from all of the bad instructions so I pulled out the Autolite 3923 plugs and they did indeed look like they had been running VERY rich. They were all gapped to about .031. I decided to replace them with the Autolite Platinum 3923 which were factory gapped at about .040. I decided to leave it at .040 because Forte had the gap much lower and the quick research I did was more in the .044 range. The .040 seemed a reasonable place to start.

I just got back from a 10 minute drive and the difference is amazing. The only thing I did was change the spark plugs and the low speed bucking is 100% gone. The super rich smell at idle is gone. Seems to be a huge improvement and I'm just getting started. The issue that I still have is that is dies on occasion when I am decelerating with the clutch in. Not cool with power steering. I'm hoping more learning with good plugs and some of the tips in this thread will get me there.

My question,
What is the right Spark Plug/Gap? Is the factory .040 about right or is there better way to figure it out?

Thanks!