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Thread: Random AFR spikes, sometimes it stays.

  1. #11

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    If your base tune is good then you could reduce your limits even more, maybe down to 5% and then you could drive the car even when it's messing up. I don't know if you have RFI noise or if you have a misfire that is tricking the ECU into thinking it needs to add fuel. It's also possible that you have an intermittent exhaust leak. Maybe a small crack somewhere and sometimes the engine will move a certain way and open up a crack in the exhaust. Weird intermittent problems are hard to track down. You just have to put your detective hat on and go figure it out. Can you switch the wideband to the other side of the engine? Sometimes that solves a weird issue. Do you have a shop in town with a scope? Even better would be a scope and a chassis dyno. Then you could load the engine and watch the eight cylinders firing. That will tell you if you have a random misfire. If the shop has a five gas setup, you can verify that your wideband is working properly.

  2. #12

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    Thanks for everyones comments. I think the best thing to do now is confirm the AFR reading with the scope and maybe on the dyno. I may try relocating the coil with jumper temporarily just to see if the data points improve. Moving the coil on a permanent base will be very hard to do because of engine space. Does anyone have a recommendation as to a coil that might emit less electric field? I've heard the E-Core winding are better. I might could build a holder and put something like a MSD 8207 in the same area.

  3. #13
    Join Date
    Oct 2017
    Location
    Los Angeles
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    399

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    There are many variables that can affect a tune and all variables are not the same or constant all the time. For example, temperatures change, manifold air temperatures change. Marked Data Points has nothing to do with EMI. Marked Data Points has everything to do with your wiring quality, crimps, wires, connections, or nicks in the wire, etc.
    1964 Chevy Nova, 383 Stroker, AFR 210 Heads, Ford 9inch w/TrueTrac/3.90 Gears, Powerglide Transmission. www.SoCalStreetCars.com

  4. #14

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    Thank you for that information on the Mark Data Points. I've been looking for a direct answer for months. That will help me very much. Do you think this could be caused by my coil being so close as Holley Tech has suggested? If it's causing interference I don't understand why other sensors are not acting up like TPS or IAC.

  5. #15
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    Oct 2017
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    Los Angeles
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    Quote Originally Posted by smithgolfdan View Post
    Do you think this could be caused by my coil being so close as Holley Tech has suggested? If it's causing interference I don't understand why other sensors are not acting up like TPS or IAC.
    I personally do not, and to answer your statement it's because you don't have EMI. Do you notice that your car runs lean or gets to 15:1 AFR when you have been driving it for a long time, or it's been completely up to temp for some time?
    1964 Chevy Nova, 383 Stroker, AFR 210 Heads, Ford 9inch w/TrueTrac/3.90 Gears, Powerglide Transmission. www.SoCalStreetCars.com

  6. #16

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    As you see in the datalogs, the random spikes to around 15 are there all the time. But I've noticed that the when it stay at mid-15 it generally is at operating temp. Although, it has happened a couple times on cold start around 160°F temperature.

  7. #17

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    Also, make sure there are no exhaust leaks upstream of the WBO2 sensor. That too will give a false lean reading. Andrew
    IG @projectgattago

  8. #18

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    Update: Hope I’m not reporting this to soon, I’ve had a number of issues I thought were corrected only to come back, but here's where I’m at now. Visited a shop with scope & dyno, checked out ignition system and all was good. Put car on dyno and placed shop’s AFR instrument in tailpipe and confirmed AFR readings except that theirs continued to get rich when mine went to mid-15 and stopped. Without getting into a lot of details finally concluded that the WBO2 sensor was fouling out (so to speak). Said they had experienced this with a handful of customers over this year and had started to install the HBX-1 Heat Sink Bung Extension. They're doing it now on all new installs.
    Bottom line: I installed the bung extension and a new WBO2 purchased from Holley and seems to have corrected the issue. Been driving around about two weeks and little over 200 miles and no issues. Need more time/miles, but right now it’s looking good.

  9. #19
    Join Date
    Dec 2009
    Location
    Connecticut
    Posts
    23,069

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    Yep, I won't use a WBO2 sensor without an Innovate Motorsports HBX-1 Heat-Sink Bung Extender. For either Bosch or NTK WBO2 sensor.
    http://forums.holley.com/showthread....ension-Harness (Read 5th paragraph under "Wideband O2 Sensor Notes")
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, M4602G aluminum driveshaft, FRPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 tires.

  10. #20

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    Good catch. Glad you did the follow up visit to a shop with scope & dyno. I knew it wasn't a problem with the wideband itself from your description, but I hadn't thought of the wideband isolator as a solution. I was pretty sure you had some sort of signal problem, but I was thinking it was due to either an air leak or a misfire. But I bet you solved it. Sounds like your wideband location was causing the WBO2 sensor to overheat. When it overheated it told the ECU that it was lean, which is why it started to add fuel. The overheated WBO2 sensor wasn't reading properly which is why your numbers didn't make sense. Once it cooled down everything went back to normal. Tough problem to debug without additional tools.

    I have started to recommend to people that they get at least two bungs installed in their exhaust system when they convert to a Sniper just so they can move the WBO2 sensor from port to port as part of a debug exercise.

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