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Thread: At wits' end with Sniper 4150.

  1. #1

    Default At wits' end with Sniper 4150.

    In June of 2018, I installed a Sniper EFI 4150 throttle body setup, with all of the gear in the master kit in my 1959 Buick, which has a 364ci V8 with dual exhaust. WBO2 sensor is installed on the driver's side of the exhaust, about 15° off vertical on the pipe. Since installation, I have consistently gotten miserable fuel mileage in comparison to the prior carb setup, never better than 13.5 versus 16-18 for highway driving. Every possible cable is shielded for RFI and the ignition system is an MSD coil with MSD 8.5 mm wires. Voltage off the alternator stays from 13.1 to 13.7 depending on what else is running in the car. All exhaust gaskets, including header gaskets, have been replaced, torqued and secured with French locks and there is no evidence of any exhaust leak upstream of the sensor. I had a failed ECU (it stopped reading the coolant temp sensor) and it was sent back to Holley for repair. Since then, no issue with the reading on the coolant temps.

    A couple of months ago, while driving on an interstate highway, the engine suddenly came to life, with beautiful acceleration and responsiveness. I noted at the time that the Closed Loop & Learn percentages had dropped into minus 17 to minus 27 percent ranges, and the fuel flow shown in pounds per hour had dropped from the 40s to 50s to a range between 27 and 32 for highway cruising. However, the next time I stopped & restarted, all of the old problems were back. A week or so ago, the same thing happened, but the condition stayed for a couple of days of really good running, acceleration, etc. Then the throttle body started dumping fuel again and performance went back into the toilet.

    I was concerned that the WBO2 sensor was bad, so I purchased a new one from Holley and installed it. After installation of the WBO2 sensor, I started from scratch with a reload of firmware for ECU and 3.5" handheld, went through the setup Wizard, set parameters for typical operation and rebooted. The engine started right up and was running more smoothly that at any point before. Acceleration and throttle response were superb and fuel consumption appeared to be in a suitable range with AFR targets being met. I took the car on a highway cruise for learning and the Closed Loop & Learn percentages quickly dropped to ranges of 0 to 7. Then, after about 40 miles, it all went to garbage again, as the Closed Loop & Learn percentages jumped up into the 30s and 40s and fuel flow was ranging from 45 to 70 pounds per hour, as opposed to the previous 25 to 35 at cruise speeds. The change over happens so quickly there is no time to capture it in a datalog file since I'm driving and can't to much with the handheld while on the road. Since then, the system has alternated between good & bad operation, mostly bad. Even operating with Closed Loop disable makes no difference. I'm about ready to rip the Sniper out and put my carb back.

    Having seen how beautifully the engine can run with the Sniper working properly, I'd really like to make this work. It is clear that the engine is getting bogged down with excessive fuel, although the AFR readings are consistent with the settings input. Idle air wants to stay at 0 percent when the engine is hot, which seems wrong, based on what I have read in this forum. Any suggestions or help would be gratefully received.

  2. #2


    I know you said you can't catch the transition from good to poor on a datalog, but when it's running well, datalog a few minutes and stop the datalog. Then sometime when it's running poorly datalog of few minutes of that. Maybe we can look at each separately and get some ideas?
    69 Camaro
    400 SBC, ProCharger D1SC

  3. #3


    Good suggestion. If I can get it running well again (it's back on the boggy side now), I'll do that. Thanks.

  4. #4


    Behavior like that is usually due to a poor electrical connection. Sounds like something is barely connected, so sometimes it gets full voltage and then other times it has a lot of resistance so it gets a low voltage signal.

  5. #5


    I managed to get datalogs recorded from good & boggy operation. The first two datalogs in the archive are while the car was running very well, with excellent acceleration, smoothness, etc. The remaining datalogs were after it started dumping fuel, bogging on acceleration, etc. It looks like the AFR goes haywire in the second set, while fuel flow is significantly higher as compared to RPM. Any insight from those more knowledgeable than I am, would be greatly appreciated.
    Attached Files Attached Files

  6. #6


    You have some minor data point issues, but honestly they are the same in the good runs versus the bad, so I don't think that's the problem. I don't know what a "bad" WBO2 sensor trace looks like, as I haven't had one go bad yet, but your AFR trace is so erratic I'd suspect that it may be bad? Hopefully others that have had know bad WBO2 sensors can chime in.
    69 Camaro
    400 SBC, ProCharger D1SC

  7. #7


    Make sure all your injectors are firing fuel into the throttle bores.

  8. #8


    I'm surprised no one informed you that you have to post your Config File too. Usually when someone has a problem, it's preached that they post Config File & datalog, but then when you do that, hardly anyone bothers to look at it. Catch 22 I guess.

    Anyway, please post your Config File that was used for the datalogs. If you changed or change your Config File, then you need to take more datalogs with the "new" Config File. Once we can view your datalog with your exact Config File, we can make educated guesses as to what it may be.

    I too noticed some data point blanks in your datalogs. To see it zoom in on an area of your datalog, right click then pick Mark Data Points. If you see straight lines with no dots, that is missing info. All of your traces (RPM, TPS, CTS, AFR, etc.) have the same missing info pattern. That "usually" means EMI or electrical problems. (Alternator noise, regulator noise not filtering AC correctly, something cycling on or off in the electrical system like an alarm, cruise control, etc.). Your missing info seems to follow a pattern of sorts. If say the RPM has a blank spot at the 21.408 second mark, all data will have a blank spot at the 21.408 second mark.

    We'll have to wait for the experts to chime in with their knowledge. Have you noticed if it only runs poorly when something is turned on like cruise control for instance, or your fan motor is on a different speed or turned off, etc? Was your radio volume up higher than normal, was your turn signal on? Danford1
    Last edited by danford1; 09-03-2019 at 12:37 PM.

  9. #9


    Config File is attached. The operating shown in the datalog files was daylight, no headlights, no radio operating, no other electrical device operating other than alternator, Sniper EFI unit and fuel pump. Brake lights and turn signals used when needed, but most of the datalog is for open road driving. The engine is a Buick Nailhead 364 cu. in. It generates a lot of low end torque, so that highway cruising speed of 70 MPH is achieved at roughly 2500 RPM. All of the fuel tables look way to rich for that, but that still would not explain why it sometimes leans out and runs beautifully and sometimes is bogging from excessive fuel. Oxygen sensor from Holley is new, roughly 60 miles of operation on it. Thanks for your help.
    Attached Files Attached Files

  10. #10


    Rereading post #1, I immediately thought of bad or loose grounds. Check all of theses ground wires, don't just wiggle them or look at them and call them good. Check them thoroughly. Take each end or ground cable off, sand everything to a bright metal, no rust, no paint, etc. Smear electrical connector grease on it all and hook it back up tight. You need a ground cable from engine block to body/frame, from body/frame to battery and battery to engine block. With sensitive electronics, you can't skimp on these grounds. You need all three. Also check ground condition on alternator to engine or run a ground wire from alternator body to block. Same for the distributor. The Sniper ECU must go directly to the battery, no exceptions.
    Last edited by danford1; 09-04-2019 at 08:34 AM.

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