Results 1 to 10 of 10

Thread: Inconsistent AFR & RPM Issues

  1. #1

    Default Inconsistent AFR & RPM Issues

    I have a '67 Buick GS400 with (you guessed it) the 400 engine in it. I recently installed the Holley Sniper/HyperSpark combo and I'm having some issues.

    First, although I have the AFR set at: 14.4 idle, 14.0 cruise & WOT at 13.0, it randomly locks on 14.9 or 15 and the engine begins to misfire. It eventually corrects itself. Once again, randomly. This issue seems to be getting more consistent as I drive it more.

    The other issue is every time I begin to decelerate to come to a stop, the RPM will stay above 1,000 and eventually only go down to 850-900 when I reach my full stop even though I have my target RPM set at 670. I found out that the only way to keep this from happening is by "burping" or tapping the throttle on deceleration before every stop. This has proven to be a bit more than a simple inconvenience, since I have the braking power of a dinosaur on rollerblades; my braking power is decreased substantially at those higher revolutions. It's almost as if the throttle gets stuck open, but the TPS reads zero. I've checked the throttle linkage travel both attached and detached from the TB and it moves freely. I've noticed that if I keep the TPS below 9, the problem doesn't occur. Anything passed that, I would have to tap the gas pedal in order to keep it from happening.

    Attached is the Config File and a datalog. Any help with these issues would be greatly appreciated.
    Attached Files Attached Files

  2. #2
    Join Date
    Feb 2020
    Location
    Wheeling, WV
    Posts
    1,336

    Default

    I'm not sure why right now, I can not unzip the files. Maybe someone else will be able to. Try to download them from this site and see if you can open them. If if not, reload them here and let's try again. My computer says they are empty, but clearly they're showing bites in them.

    One of the first fixes that comes to mind is this. It's common to need more spring psi on the secondary throttle shaft. In your case it'd make sense you fall in this category based on your symptoms. There are other digital issues that may need to be adjusted to help your situation, but until I can see the GCF and datalog I don't want to get into it right now.

    As far as the AFR appearing to stick at 15:1, are you sure you do not have any exhaust leaks? Before I go crazy with what's possible, I'd like to see the datalogs.

  3. #3

    Default

    I'm not able to extract the zip file either.

  4. #4

    Default

    My apologies. Hopefully it works this time.
    Attached Files Attached Files

  5. #5
    Join Date
    Feb 2020
    Location
    Wheeling, WV
    Posts
    1,336

    Default

    I didn't look at the GCF yet, but I did peak at the datalog. My first gut feeling is you have a loose injector connector. I'll study it some more soon.

  6. #6

    Default

    Inductive Delay for your HyperSpark distributor is 0.0, which might be a problem. Have you verified spark timing with a timing light at different (higher) RPM? If not, you should do that. You have various qualifiers on your Closed Loop & Learn which you should get rid of. You have Learn turned off at idle which doesn't seem smart for an engine like yours. If you look at a graph of your ignition timing, you'll see that you don't have a timing curve, you have a timing cliff. That isn't a good idea for a timing table, so you should fix that.

    However, I don't have an answer for your weird fueling issue. I suspect some sort of mechanical failure. Perhaps a bad injector, bad injector driver or loose injector connector. It looks like the system thinks it's lean and adds a bunch of fuel, but the fuel most likely either isn't being injected, or else it isn't needed. Could also be a faulty wideband O2 sensor. If the wideband O2 sensor had a loose wire or a poor connection it could mess up the signal and cause the ECU to react in weird ways.

  7. #7

    Default

    I did check the timing when I first installed the HyperSpark ignition system. It was over advancing so it was suggested that I set the Inductive Delay at 0. After that, I ran the RPM up 4,000 and it was working fine. Ideally, what should the Inductive Delay be at? Also, what qualifiers do you suggest I remove? I'll look into turning on idle Learn and changing the timing to curve. I think it's like that because I set it to Simple instead of of the 2D Table, since I'm not too familiar with timing settings. :-/
    At this point I know enough to be dangerous, so I'm being overly cautious so I don't send piston flying due to pre-detonation mixed with the occasional 15.0 to 16.2 A/F Ratio I observe while on the freeway. Thank you.

  8. #8
    Join Date
    Dec 2009
    Location
    Connecticut
    Posts
    28,793

    Default

    Quote Originally Posted by M.A.R. View Post
    Ideally, what should the Inductive Delay be at?
    The Inductive Delay should not be zero: https://forums.holley.com/showthread...528#post254528 (Related Forum Post)

    Also, what qualifiers do you suggest I remove?
    Check your Closed Loop/Learn Parameters. "Enable Closed Loop" and "Base Fuel Learn Enabled" are the only two parameters that need to be check marked.
    https://forums.holley.com/showthread...289#post233289 (Related Forum Post)
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS T/W 11R 205 heads, 232°-244° duration/.623" lift/114° LSA camshaft, 12:1 C/R, TFS R-Series FTI ported intake, BBK 80mm T/B, Holley Dominator MPFI & DIS, 36-1 crank trigger, 1x cam sync, 200A 3G alternator, Optima Red battery, R134a A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans, Frostbite 3-core aluminum radiator, Pypes dual 2.5" exhaust, off-road X-pipe, shorty headers, -6AN fuel system plumbing, Walbro 255 LPH pump, S&W subframe connectors, BMR upper & lower torque box reinforcements, LenTech Strip Terminator wide-ratio AOD, 3000 RPM converter, B&M Hammer shifter, Stifflers trans crossmember & driveshaft safety loop, FPP aluminum driveshaft, FPP 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 M/T Street Comp tires.

  9. #9
    Join Date
    May 2014
    Location
    Bostwick, GA
    Posts
    416

    Default

    Fuel psi is?
    Injector Inspector
    USAF 1960-1964
    Drag racing since 1955

  10. #10
    Join Date
    Dec 2009
    Location
    Connecticut
    Posts
    28,793

    Default

    Originally Posted by Danny Cabral
    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? Check for ignition misfires/RPM signal problems, 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.
    Also, the Holley Sniper EFI will intermittently inhibit Closed Loop at idle, if the AE vs TPS/MAP RoC Blanking values are set too low.
    http://documents.holley.com/techlibrary_199r11259.pdf (Holley Sniper EFI Help Manual)
    http://documents.holley.com/199r11369.pdf (Holley Sniper EFI Troubleshooting Guide)
    https://forums.holley.com/showthread...8356#post88356 (Holley Sniper EFI Fuel Pressure Tester/Gauge)
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS T/W 11R 205 heads, 232°-244° duration/.623" lift/114° LSA camshaft, 12:1 C/R, TFS R-Series FTI ported intake, BBK 80mm T/B, Holley Dominator MPFI & DIS, 36-1 crank trigger, 1x cam sync, 200A 3G alternator, Optima Red battery, R134a A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans, Frostbite 3-core aluminum radiator, Pypes dual 2.5" exhaust, off-road X-pipe, shorty headers, -6AN fuel system plumbing, Walbro 255 LPH pump, S&W subframe connectors, BMR upper & lower torque box reinforcements, LenTech Strip Terminator wide-ratio AOD, 3000 RPM converter, B&M Hammer shifter, Stifflers trans crossmember & driveshaft safety loop, FPP aluminum driveshaft, FPP 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 M/T Street Comp tires.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
About us
Holley has been the undisputed leader in fuel systems for over 100 years. Holley carburetors have powered every NASCAR® Sprint® Cup team and nearly every NHRA® Pro–Stock champion for four decades. Now, Holley EFI is dominating the performance world as well as our products for GM's LS engine. Holley's products also include performance fuel pumps, intake manifolds & engine dress–up products for street performance, race and marine applications. As a single solution, or partnered with products from other Holley companies - Hooker Headers, Flowtech Headers, NOS Nitrous, Weiand, Earl's Performance Plumbing, or Diablosport - Holley products can give you the edge you need over the competition.
Join us