Sniper Unresponsive High Idle - Solution!

[cmyer]

I've had good success helping our customers solve high idle issues on their Holley Sniper EFI system installations. However, it seems that even after we resolve all of the obvious issues and are able to get the idle down about to where we want it, the ECU just seems to be fighting us to get it just right.

I finally called Holley Tech and asked resident genius and Holley Tech icon Woody Warren what he thought. He had experienced the exact same thing. On a previous installation he finally realized that it wasn't a vacuum leak or a throttle plate issue. It was the ECU (that was programmed for a lower target RPM) actually driving the RPM higher than the target.

A conversation with engineering ensued and they found an unexpected issue. The RPM setting on the lowest temperature of the Idle Speed Curve (−40°F), was set way lower than the RPM at the temperature immediately above it. And, although it shouldn't have any impact on the hot idle, that one setting was confusing the ECU. They moved the setting up, and voila, problem solved.

If you are interested in more info on how to fix this see the link below. I had already been documenting the Sniper EFI idle troubleshooting techniques in our EFI Pro Hangout, so I've added details & images on this setting there. If this works for you please post either here or there, and let us know what you find. I hope this is helpful!
http://www.efisystempro.com/efi-pro-...roubleshooting

[Danny Cabral]

Thanks for posting that Idle/IAC resolution, Chris. It was becoming a common problem.
http://documents.holley.com/199r11193.pdf (Holley Sniper EFI Quick Start Manual - "Idle Setting/Throttle Plate Setting", Page 12)

Holley Sniper EFI Quick Start Manual: IDLE SETTING/THROTTLE BLADE SETTING Once the engine is up to operating temperature, the idle speed can be set to what was configured in the Wizard. To do this, open up the Initial Startup gauge screen that was used in section 17.0. With the vehicle in neutral, adjust the idle screw until the IAC Position reads between 2 & 10%. While adjusting the idle speed screw, if the TPS Position begins to read higher than 0%, 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!

If blocking off the IAC air inlet port results in improved idle/deceleration operation, then problem is IAC related. 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. Ensure the TPS Position always return to 0% at idle, or else the IAC Hold Position is activated and raises the idle. A lot of vehicle applications don't like the IAC Hold Position (Idle ICF) too high. Install a throttle return spring (LINK). If you'd like to eliminate the IAC valve as a problem, temporarily block off the IAC air inlet port with a strong piece of tape.