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Thread: Oxygen Sensor? Fails way too early.

  1. #71
    Join Date
    Dec 2009


    Is the Sniper EFI Learning? Is the ignition timing synchronized? Is the fuel pressure 58-60 psi (LINK)? IAC Position of about 5% at hot idle? Also check for an ignition misfire/RPM signal problem, exhaust leak upstream of WBO2 sensor, or if the WBO2 sensor (or other sensor) has failed and corrupted the Learn Table. Look at the Data Monitor/Gauges. (Holley Sniper EFI Help File) (Holley Sniper EFI Troubleshooting Guide) (WBO2 Sensor Test At End Of "Wideband O2 Sensor Notes")
    May God's grace bless you in the Lord Jesus Christ.

    '78 BRONCO: 508" stroker, TFS heads, 11:1 comp ratio, Dominator MPFI & DIS, cold air induction, Spal dual 12" fans/aluminum radiator, dual 3" exhaust/Magnaflow mufflers, Moroso vacuum pump, Accusump, engine oil & trans fluid coolers, 100HP progressive dry direct-port NOS, A/C, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, Cage long radius arms, traction bars, 4" Skyjacker lift, 35" mud tires

  2. #72


    Yes, Sniper is Learning, yes the timing is synced. Yes, IAC is good at hot idle. Fuel pressure is 60 psi. No exhaust leak. Nothing has changed except the distributor since the ECU failure. Car ran perfect up until that point. Changed the WBO2 sensor, no change. I have a short datalog in the driveway. From starting the car, to a free rev of about 3000 RPM, to decel & die.

    I guess I just don't want to go on a wild goose chase, if I still have an ECU issue. I could pull the distributor and put the HEI back in, but again, a lot of work if it's not related. Not sure if this link will work, but here's the datalog file:

  3. #73


    I would run back through the Dual Sync Distributor installation.
    Check all the plug wires. Are you using the coil driver or MSD box?
    Getting the proper ignition synchronization can be a chore.

    Your ignition timing is all over the place, along with your AFR. You ran the Wizard again and setup all the new parameters for the dual sync without issues, correct?

  4. #74


    I did with no change, so I went back to the last good time, added the dual sync distributor parameters. Using the coil driver. Going to start over with the Wizard.

  5. #75


    Looks like I'm in the same boat sort of. Mine was running fine before I sent it in (if I took it out of Closed Loop, so it would ignore the false 35.6 AFR), and I have made zero changes. I put on the repaired Sniper, ran the Wizard, and now it's running like junk. I don't have a known good file to load. I have zero miles on this thing. Oh, the only change I made was a 1/4 inch spacer that everyone was recommending, so I could avoid the whistle when I do get it on the road.

  6. #76


    Great, that's not good news. It seems to point to the unit, NOT something we've done.

  7. #77


    So I went to redo the Wizard a few times and it kept hanging up, and I would shut it down and pull the SD card & reinsert. Finally, it programmed and is back to running normally as can be expected for a fresh Learn.

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