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Thread: Surging at Idle and light acceleration issue.

  1. #1

    Angry Surging at Idle and light acceleration issue.

    Sniper has been on my car for a while now. I installed in April, and until about a week or so ago it's been flawless. Lately though it's developed a strange surge at idle and light acceleration. If I stay in it and keep the RPM high it seems to accelerate fine, or better, but this surge action has me wondering what's going on.

    Car: 1968 Camaro SS, 454 GM crate engine (bored .030"), 292 Crane cam, Holley Dominator high rise intake, 700R4 transmission. Nothing has changed since the install (wire interference can likely be ruled out). MSD coil (no coil control, yellow wire to - coil) and a Flame Thrower 3 distributor. Timing was set by dyno guy when it had the carb, vacuum advance to distributor port on Sniper. He said timing should be perfect for Sniper (and maintains that).

    Here's a link to a few of my config files. BASE MASTER is the original tune I setup with the Wizard when installed. 68 SS 100min AETPS is the same tune, but I flatlined the AE vs TPS RoC to 100 (instead of it going down) based on some forum post I read. That did seem to cure the stumble I was getting when I punched it hard. I've ran both tunes, plus did a fresh Wizard file and the surge issue is there with any of them. The most recent datalog files (11, 12, 13) are from today when it seemed to get really bad. Granted it's been hot as heck out (water gets up to 220°F when in traffic) so maybe it's heat related, not sure, but it was doing it this morning when it was cool out. I've tried to play with the Sniper EFI software but I'm, frankly, not sure what I'm doing. Would anyone care to take a look and let me know your thoughts? Thank you!
    Link to Google Drive with files: https://drive.google.com/open?id=1-k...jK25qXAfY2dXNb
    Last edited by Proflyer; 07-18-2019 at 05:15 PM.

  2. #2

    Default

    I looked at the datalogs, but honestly it's hard to tell where the surge is. I'm sure it's evident in the car, but the RPM doesn't seem to very that much. You do have some mild lean spikes, but not anything crazy. Can you pinpoint a time in one of the datalogs where the surging felt really bad? Maybe specify which datalog and what time mark?

  3. #3

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    Since the surge developed over time I'd suspect a mechanical part which is the root cause. For example, a fouled spark plug will misfire and start a whole ripple effect. The wideband will see the misfire and adjust the AFR, which then causes the engine to run poorly which causes the wideband to make another adjustment and pretty soon the engine is rocking back and forth as it tries to sort it all out. You have to go find the root cause. Look at the plugs, check the plug wires, check for vacuum leaks, etc. Look through your datalogs for the root cause. It's in there somewhere, but it can be hard to find.

  4. #4

    Default

    I was thinking the same. I wasn't sure if the datalog would pickup a misfire, but it does sort of feel like one, albeit intermittent. It's been sitting for two hours and is still too hot to even check. 100°F+ here in Denver today! And now that I think about it. I was checking my plugs to see if they were fouled a week or two ago. Previously I had a carb which kept flooding. Dyno guy said plugs were likely fine, but to check them after some time with the Sniper. I did so, and they all looked great. In the process of that, one plug wire came apart so I had him make me a new one. I wonder if that wire isn't crimped right or something and causing a misfire. I'll pull that plug to check it. If that's the culprit, it'll be fouled for sure.

    The surge may not change the RPM enough to show up in the datalog, but it does seem to correlate with the AFR spikes you see. It might misfire, WBO2 sees super rich, tries to compensate by going lean, then sees it's too lean and creates that never ending loop. I'll report back. Thanks gents!

  5. #5

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    Well that's not supposed to look like that. As my old man used to say, "It's always the last thing you messed with!" Plug surprisingly isn't fouled though. Boot was resting right on the header. Rubber was all hard from arcing and crumbled right off. Hopefully that's it, cheap & easy fix! Also, the WBO2 is on that header bank. Probably wouldn't catch it if it was on the other side.
    Click image for larger version. 

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    Last edited by Proflyer; 07-18-2019 at 08:30 PM.

  6. #6

    Default

    I think you found your problem! LOL.

  7. #7

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    Ha, ha right? Hopefully. *Bangs head on shop table.*

  8. #8

    Default

    A lot of the "Sniper problems" on this forum turn out to be something else. Vacuum leaks, spark plugs, spark plug wires, poor wiring, etc.

  9. #9
    Join Date
    Jan 2010
    Location
    Brisbane, Australia
    Posts
    1,533

    Default

    You need some fire sleeves on those plug boots. Replace the boots, and fit some sleeves. Gary
    Regards, Gary

  10. #10
    Join Date
    Dec 2009
    Location
    Connecticut
    Posts
    22,683

    Default

    I was thinking the same thing (LINK).
    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.

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