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Thread: Problems Since First Start

  1. #1

    Default Problems Since First Start

    Hi there! New here and having problems with my new Sniper. Car is a '81 TransAm with a '75 467 Pontiac big block, around 9.5 C/R and a choppy sounding cam. Not sure about engine specs because I bought the car like this and the previous owner wasn't sure about anything, but with a Holley 4BBL it worked great. Shaky idle, but excellent acceleration without bogs or flat spots, no smoke whatsoever and good cold starting. So I installed a Sniper EFI just hoping to get a little better fuel mileage. I did everything according to the manual, fuel pump recomended by Holley and initial adjusts exactly as outlined by Holley. Still have to check the fuel pressure, but I'm pretty sure the return line is not being a problem since I bypassed it and the problem didn't change a bit.
    Since the first start if I try to run it in Closed Loop the CL Comp % starts to climb and the engine starts to run rough. Sometimes Closed Loop goes straight to 100% and stays there until the engine stalls, and sometimes it climbs to around 60 or 80%, and then goes down to 0 and inmediately starts to climb again. If I touch the throttle it goes to 0 but starts to climb again. In Open Loop it idles pretty good, but the AFR is clearly wrong since I can see black smoke coming out the tailpipes. I haven't touched anyting but the required by the manual in the Startup, After startup and Idle setting/throttle plate setting sections. I have a brief datalog I'll try to post. Any idea what am I doing wrong or what could I forgot to set?
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    That's enabling and disabling Closed Loop.

  2. #2


    Looking at the graph, when the Closed Loop Compensation starts to open, shouldn't the ARF register a leaner condition? I mean, if a lot more air is entering, it should be spikes in the AFR graph right? If so, I may have a defective WBO2 sensor or an extreme misfire located?

  3. #3


    In order for us to evaluate we need a copy of the current configuration file downloaded from the ECU. You must manually do this using the Save As function on the handheld because the Sniper doesn’t update or use any configuration on the SD card. The current tune is only held in Sniper memory.
    You also need to zip and post the datalogs you displayed in picture form. With the Config File and datalog files, we can overlay the two and identify any tuning issues that might be causing the problem.
    Fuel pressure can indeed be causing your problem. Since the return line is connected to the regulator outlet, removing the return line will not provide a positive confirmation that the regulator is working properly. If Closed Loop is going to 100% and it’s not a tuning issue, you likely have inadequate fuel pressure or there's a strong chance that you have a loose injector connector. The Sniper doesn't monitor pressure or flow. It issues commands assuming that the pressure is correct and that all four injectors are functioning. If one or more injectors are not flowing the Sniper will command more and more fuel to try to reach your targets.
    Another potential problem causing high Closed Loop values is the placement of your WBO2 sensor and the integrity of the exhaust system from manifold/header gaskets to pin holes at the WBO2 bung to leaks after the sensor. Some have had issues when attempting to use the clamp-on sensor mount as it can be hard to keep them leak free.
    Please report back on your fuel pressure. Don’t assume because you have new components that it has to be correct. Also describe your WBO2 sensor mounting location and method.
    Post your Config File and the actual datalog after you zip them and we'll take a look.
    Checking the injectors is pretty easy. With a helper, remove the air cleaner and look down over all four barrels. Have the helper turn on the ignition. After a short period you should see all four injectors provide a prime shot. If one or more does not you likely have a loose injector connector. If the engine will run, you can start it and observe the fuel flow from each injector. The flow should be identical.
    Last edited by GPatrick; 05-10-2022 at 08:45 AM.

  4. #4


    It's very hard to read your datalog on the screen, but it looks like the engine is idling with an actual AFR of 16? Is that correct? And the Sniper doesn't seem to be controlling the AFR. If that's true then you have some sort of a mechanical problem. Most likely a bad injector, but it could be a bad fuel pump, clogged filter, etc.

    If you zip the DLZ file and post it on here we can open it up and look at the details and provide you with better feedback.

  5. #5


    GPatrick, here goes the Config File and the datalog. Will look for a fuel pressure gauge ASAP. I checked the injectors and all four at least do prime. The WBO2 sensor do not show any sign of leaking and the exhaust is in good shape, but I'll move the sensor closer to the manifold and weld the bung just in case.
    AndyF, yes, idling AFR is around 16 and doesn't get better. Thanks guys!
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  6. #6


    The datalog is showing some crazy information so it is a little hard to tell exactly what's going on. There are a few things you can look into. First, when it is idling the IAC is open pretty far. You may need to turn in the idle screw (open the throttle blades) one to two turns so the IAC has a chance at trying to control idle speed. Turn it in two turns while the engine is off. When you turn on the ignition the Sniper will perform a TPS Autoset. See if things improve. The system did not go into Closed Loop for about 40 seconds and after that it was spotty. The high IAC value may be one of the reasons that it doesn't want to go into Closed Loop.

    Your RPM signal as well as your IAC trace show signs of noise. This is easiest to see shortly after the engine starts. There are sharp one datapoint wide spikes in RPM with no throttle input. Additionally, they're so short in duration that it is not possible for the engine to respond that quickly. In one case there is a blip in the RPM as well as the IAC which would seem to indicate that there some sort of noise/interference present. Check your yellow wire on your coil − input and make sure it is routed away from any of the spark plug wires. What distributor are you running? Some distributor/coil combinations may not work well with the coil − input but we need to know what you have.

    If I had to hazard a guess at this point, it appears that you have low fuel pressure. In Open Loop the AFR is high at 16 and when it goes into Closed Loop it is trying to add fuel with no success.

    However, if I recall there have been some cases where a faulty WBO2 sensor provides a constant reading of 16 or so. Usually a bad sensor will read in the mid 30s, but I've read about a failure mode where they are stuck at 16. Others may have more experience with this. When we see fuel being added, but no change in the AFR this would indicate false or bad WBO2 reading.

    So, the high IAC value may be the result of a false AFR signal rather than the throttle position. I would still see how the system responds to turning the idle screw in one to two turns. Check your fuel pressure and try to search for false/bad WBO2 sensor readings.

    The Config File provided is likely the default Wizard Config File that is on the SD card. You need to look in the saved GCF file folder on the SD card to find the file you downloaded. When you use the Save As you can give it a unique name so you'll be able to find it. The clue is that the Learn Table is empty. The datalog shows that some learning is taking place. It's helpful to see what the Learning values are as this can identify potential fueling related issues.
    Last edited by GPatrick; 05-10-2022 at 01:52 PM.

  7. #7


    OK, I checked fuel pressure and it reads very close to 60 PSI at priming. I can't start the engine right now because I had to remove the oil filter to weld the WBO2 sensor bung. I put it much closer to the manifold collector and I'm sure it's air tight now. (Despite how it looks! No easy to weld down/up there.) The distributor is a GM HEI that looks old, but has worked just fine so far. The pink wire for the switched +12V and the yellow for the tach signal goes as far as possible from the spark plug wires, and the pink one goes directly through the firewall and under the carpet to the fuse block. Maybe I can install a relay for that and avoid going to the fuse block just in case. I'll get an oil filter and start the engine to get a fresh datalog after these little changes.
    In the previous datalog the flat part of the IAC graph is because I started with Open Loop and then I disabled it. As soon as Closed Loop starts to work, the spikes start and just to avoid engine stall I hit the throttle. After a few spikes I enabled Open Loop again. In the next datalog I'll let the engine and ECU do what they want, so maybe you can have a less confusing graph. Sorry, first time dealing with EFI!
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  8. #8


    I think you have a fuel delivery problem. The Sniper thinks the engine is 17:1 AFR and it's dumping almost 20 lbs/hr into the engine at idle to enrich it up. That is three times what your engine needs at idle, so I doubt that it's actually injecting that much fuel. If it was injecting that much fuel you would have gas in your oil and the plugs would all be fouled. I think what's happening is that your engine is starved for fuel. The Sniper thinks it's injecting fuel, but it actually isn't.

  9. #9


    Along those lines, I'd look down the bores while the engine is running and check to see that all four barrels have fuel spraying into them. Andrew

  10. #10


    I just started the engine after relocating the WBO2 sensor, updated the SD card contents, checked the fuel pressure (60 PSI firm) and the only thing I see changed is the IAC climbing to 50% instead of full 100% in Closed Loop, but the result is the same. After some spikes, the engine stalls. In Closed Loop, it works almost good, but the EFI is clearly sending much more fuel than needed. Idles rough and the shop starts to fill with black smoke. I have another Sniper (2BBL) here so I guess I'll try installing the WBO2 sensor from that one and look again for vacuum leaks. I have a couple more datalogs. One in Open Loop and the other in Closed Loop and the Config File just in case someone wants to take a look. Thanks for the input guys!
    Desktop (1).zip
    Last edited by Danny Cabral; 05-11-2022 at 06:48 PM.

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