Sniper EFI Erratic AFR

[NikoLovell]

I have a '66 Ford Mustang with a 347 and a 5-speed manual transmission. My AFR is very erratic, it jumps around and frequently gets pegged at both rich and lean. There are no exhaust leaks. I attached my Config File, a datalog of my AFR at cruise, and a longer one from my drive to work. After reading a bunch, I learned that a bad CTS could cause this, as well as a fouled WBO2 sensor. Should I start with replacing these? Thank you for your time and help.

[Danny Cabral]

Originally Posted by Danny Cabral The Target Air/Fuel Ratio Table & Base Fuel/Timing Table (and MAP kPa & RPM axes/scales) should be configured using the Sniper EFI software: In the Sniper EFI software (LINK), Target Air/Fuel Ratio Table (Fuel ICF) & Base Timing Table (Spark ICF), select "2D Table" Type (not "Simple"). The Target Air/Fuel Ratio Table & Base Timing Table can then be properly configured & tuned for any engine. I always suggest taking notes of your current distributor's ignition timing specs/curves beforehand, and then program the Base Timing Table accordingly. https://www.holley.com/support/resou...Fuel_Injection (Sniper EFI Software & Holley 558-443 CAN/USB Dongle) https://forums.holley.com/showthread...679#post100679 (Sniper EFI Optional Comm/Data Cable Accessories) https://www.efisystempro.com/efi-pro...timing-control (EFISystemPro.com - ECU Timing Control, From Simple To 2D Table)

Originally Posted by Danny Cabral Is the Sniper EFI Learning? Is the ignition timing synchronized (LINK)? Is the fuel pressure 58-60 psi (LINK)? IAC Position of about 5% at hot idle? Vacuum leaks? Check for ignition misfires/RPM signal problems? Wiring issues (LINK)? Fixed orifice PCV valve (LINK)? Exhaust leak upstream of WBO2 sensor, or if the WBO2 sensor (or other sensor) has failed and corrupted the Learn Table? Base Timing Table and/or Target Air/Fuel Ratio table programmed wrong? Analyze all sensors on the Data Monitor/Gauges? The Holley Sniper EFI will intermittently inhibit Closed Loop at idle, if the AE vs TPS/MAP RoC Blanking values are set too low (LINK). http://forums.holley.com/showthread....5760#post45760 (Scroll down to "Typical Idle/Running Issues".) http://documents.holley.com/techlibrary_199r11259.pdf (Holley Sniper EFI Help Manual) http://documents.holley.com/199r11369.pdf (Holley Sniper EFI Troubleshooting Guide) https://forums.holley.com/showthread...8356#post88356 (Holley Sniper EFI Fuel Pressure Tester/Gauge)

Overlay the datalog onto your Global Config File (GCF), and pay special attention to the center paragraph in blue print:

Originally Posted by Danny Cabral Quick Datalogger Information: Always provide data, not just symptoms. Is the AFR & ignition timing optimized? Overlay the datalog onto your Global Config File. Ensure the Target A/F Ratio table is properly programmed for your engine. Ensure the ECU is "Learning" (Learn Table LINK). Scroll through the datalog to the problem area. Then look exactly where this happens on the Base Fuel & Timing Tables. Scrutinize: RPM, MAP, MAT, TPS, CTS, IAC, Target AFR, AFR Left, CL Comp, Ignition Timing, Duty Cycle, Fuel Flow, Fuel Pressure & Battery. Using the Holley EFI software (LINK), look at where the live cursor moves to during this occurrence, and manually tune that area of the Base Fuel Table (enrich or lean) & Base Timing Table (optimize ignition timing). I find the most helpful datalog function, is overlaying the datalog on your GCF. I'm in the habit of using the datalog Overlay feature every time I review a datalog. Click on "Datalog" (on the top Toolbar), "Activate Overlay", then "Open Data Log". You can literally "playback" a recorded event, and watch it as it happened on any screen. Minimize (shrink) the datalog window, and move it to the bottom of any GCF screen. Then click & scroll anywhere on the datalog, and watch it playback on your GCF (EFI software). http://documents.holley.com/techlibr...9r10543rev.pdf (Holley EFI Datalogger Instructions) https://forums.holley.com/showthread...s-amp-Datalogs (Datalog Information - Read "NOTES") https://www.youtube.com/watch?v=iqHO...C6FEA0BB99AF17 (How To Record & Email A Datalog) https://forums.holley.com/showthread...7531#post77531 (Closed Loop Datalog Tuning - Posts # 2, # 4 & # 6) http://forums.holley.com/showthread....2523#post62523 (Read 4th & 5th Paragraphs - Smooth Fuel Graph After Transfer Learning)

[GPatrick]

What intake manifold are you running? Your IAC Hold Position is 40% and you have a progressive linkage selected. On some (not all) dual-plane intakes, this provide uneven fuel distribution to the cylinders since you have air and fuel coming in from the front throttle plates and only air coming in from the IAC in back. This is also influenced by whether or not there's a full or cut down center divider and by the type of spacer you may be running. One quick check would be to change your IAC Hold Position to 20% and see how it does and then even 10% for the sake of troubleshooting. Your Target AFR in the erratic datalog example is 14.4. Since you are using the 2D Target AFR table you could see how it responds to 14.0, 13.5, 15, etc. I would start with the IAC first.

Once you describe your intake we can discuss spacer options.

The other variable we can't see is your timing. If you hold it at 2000 RPM as seen in the datalog, what's your actual timing?

When there's a fouled WBO2 sensor you'll often see AFR values in the mid 30s. The AFR variations in your datalog seem to indicate more of an uneven firing condition.

When you let off the throttle the system goes into Open Loop, but then the datalog is stopped. If possible please record a datalog of a warm start. Start the datalog after you turn on the ignition and then start the engine. Let it idle for 10 or 15 seconds. This will allow us to see the ambient MAP reading and the conditions at idle.

You have selected a mild cam, but what are your actual cam specs, duration at .050" and overlap?

The potential problems show up most often when the engine is fully cold and sometimes at higher temperatures. To test, on a fully old engine after sitting overnight turn on the ignition and before starting navigate to the monitors. Compare the CTS to the MAT. They should be within a few degrees. If the CTS reads 10°F or more higher, then the CTS should be replaced. In some cases, the faulty Holley supplied CTS can read low at higher temperatures, but the cold condition is the best way to determine if the CTS is bad. The cold error will make the Sniper think that the engine is warmer than it actually is and this affects cold starts and warmup. Once up to temperature, there often aren't any problems.

[Danny Cabral]

https://forums.holley.com/showthread...5359#post85359 (Holley Sniper EFI Dual-Plane Intake Manifold Use)
https://forums.holley.com/showthread...898#post227898 (Holley Sniper EFI Replacement CTS)

[NikoLovell]

I'm running a dual-plane Performer intake with a Trick Flow 1" tapered spacer. I attached a photo of my spark plugs (around 1,000 miles on them).

Mechanical timing is 12° at idle and 24° at 2000 RPM. However, the vacuum advance is running on manifold vacuum so actual timing is 20° at idle and 40° at 2000 RPM.

I just purchased a new CTS because mine reads 20-30°F hotter than actual temperature.

I drove it with IAC Hold Position set at 20% and it made no difference in AFR, but the car was easier to drive.

The cam was a custom grind and I do not have the build sheet so I can't give the specs.

[GPatrick]

It could be that your timing is coming in too early, especially at 2000 RPM with no load (high vacuum). Disconnect your vacuum advance hose and block the port on the Sniper. Take a log at 2000 RPM no load and compare. Are you using the ported or manifold vacuum ports on the Sniper? If using manifold vacuum, swap to the ported vacuum and compare.

What type of PCV valve are you using. On the driving datalog there is a period of idle and it's showing a steady MAP variation, and the Sniper is responding based on the fuel map by adding or pulling fuel as the MAP varies. If you're using a spring type PCV valve, swap to a fixed orifice. This has stabilized MAP readings on some applications. Or it may be that you need to do some live tuning and adjust your AFR and timing. The cam may also be contributing to the variation, but I would expect a more random pattern.

For another test, try hold the car in gear and 2000 RPM while driving up a slight grade. The AFR numbers under load are likely a better indication of any potential issue compared to a no load steady 2000 RPM on the driveway.

[NikoLovell]

First of all, I appreciate your help immensely. Thank you for taking the time to help me out.
I switched to ported vacuum and swapped the CTS and observed no difference. The reason I switched to manifold vacuum is because the ported vacuum only works if the secondaries are open, and since I almost always drive it under 42% throttle, the vacuum advance wouldn't work.
I am using a PCV valve with a spring. Should I try one that is just open?
I am going to pickup another set of plugs. What do you think about the current ones?

[Danny Cabral]

https://forums.holley.com/showthread...637#post243637 (Holley Sniper EFI Fixed Orifice PCV Valve Thread)

[GPatrick]

I'm not a plug reader, but it looks a little uneven from plug to plug and maybe evidence of a little oil. Hopefully a master plug reader can give you a better assessment. Have you retorqued your intake manifold since the original install? Sometimes they can loosen up after a number of heat cycles as the gasket compresses. This can sometimes give a slightly uneven MAP reading and can allow some oil to be pulled up from the lifter galley.

I used a progressive linkage on my Sniper install and didn't have any issues, but I was using Sniper timing control. Several on this site recommend the throttle arm extension over the progressive linkage, but sometimes there's not room for the extended arm under the air cleaner.

Have you tried running it without vacuum advance to see what happens at 2000 RPM no load?

[Danny Cabral]

https://forums.holley.com/showthread...659#post255659 (Holley EFI 20-16 Throttle Lever Extension)

[NikoLovell]

I pulled the plugs and wires out of the car because I'm replacing them tomorrow. Plug wire # 3 had a crack in the insulation right next to the header. No vacuum advance at 2000 RPM (no load) showed the same instability in the AFR. Intake is tight and there are no gasket leaks anywhere. I'll also pickup a fixed orifice PCV valve and get back to you.

I tried using the factory 1:1 throttle linkage with the extender and the car was still undriveable. I'm currently using both the progressive linkage and the throttle lever extender, as it is the only combination that allows for smooth driving. Thank you both and have a great rest of your day.

[NikoLovell]

Changing the WBO2 sensor and adding an extender fixed the issue. Thank you again for your time and help. You're greatly appreciated.