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Thread: Cold Start Sensor Datalog Spikes?

  1. Default Cold Start Sensor Datalog Spikes?

    Hi all. I'm trying to understand a cold start datalog where it seems several of the core sensors, as well as RPM, Timing, etc are showing random spikes in the graphs instead of being clean. What is odd is that when these spikes show up, it's not just one sensor (I.E. TPS), if you look at the screenshot, you'll see TPS spikes to almost 20%, and all the other spikes across MAP, IAC Position, AFR Left, Timing, RPM. At the same time the Battery volts is steady as she goes from 14.4-14.7 volts. Note link below screenshot should bring up larger image if needed. I don't think this is just a matter of adding "filtering" to the graphs to smooth these out?

    Setup is:
    Holley HP Stealth Ram MPFI
    Holley Dual Sync Distributor
    CNP (https://forums.holley.com/showthread...nc-Distributor)
    NTK Wideband

    I was seeing TPS spikes during cranking some time ago (https://forums.holley.com/showthread...During-Startup), but even after replacing the TPS with new GM part it still exhibits that behavior.

    Is there something I should be checking that is common across all these sensors? I have the wiring done extremely carefully with ECU power leads direct to battery, grounds for the CNP harness direct to rear of cylinder heads for each bank respectively.

    There's only the one (loose 18 AWG) black ground wire from the Main Harness that's also on the rear of driver cylinder head. I use star washers for these, of course to ensure good ground.

    Of note, is the CTS & MAT sensors are not spiking in any way, while the MAP & TPS spike in lockstep.

    Thoughts? I've been datalogging cold starts so I can get the MAT/CTS enrichment tables tuned, but seeing this in the datalogs makes me question if there's something else going on I should be concerned with. Thanks in advance.

    Attachment 2680
    http://chilp.it/d4721c5

    HP EFI V4, 388cid Stealth Ram, 1000 CFM 58mm throttle body, Holley Dual Sync Distributor. LS Coil Near Plug, 1 bar MAP, 48 lb/hr Holley EFI injectors, 43 psi

  2. #2
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    Quote Originally Posted by 383_StealthRam View Post
    Of note, is the CTS & MAT sensors are not spiking in any way, while the MAP & TPS spike in lockstep.
    The CTS & MAT are thermistors, they only share the Sensor Ground. Since the TPS, MAP, Fuel & Oil sensors share the same +5V & Ground, I'd disconnect each sensor one at a time (laptop "Online" with ECU), and see if one unplugged sensor rectifies the fault. I'd try troubleshooting these sensors key-on/engine-off.
    https://forums.holley.com/showthread...ensor-Problems (Related Forum Thread - Read This!)
    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.

  3. Default

    Hi Danny, as always thank you for the reply.

    After posting, I was reading some of your other posts, and went back and zoomed in in the MAP/TPS RoC in the datalogs, and was able to see that the TPS RoC was happening just a sec or so before all the other spikes. (Too sensitive, I assume?) I went into the Fuel Modifiers and increased my TPS RoC setting by 1.0 (7.5 up to 8.5), and it seems to have solved it. Seems once you make a post here, you can't see or delete it until it's moderated? Sorry to have bothered you.

    HP EFI V4, 388cid Stealth Ram, 1000 CFM 58mm throttle body, Holley Dual Sync Distributor. LS Coil Near Plug, 1 bar MAP, 48 lb/hr Holley EFI injectors, 43 psi

  4. #4
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    Quote Originally Posted by 383_StealthRam View Post
    Seems once you make a post here, you can't see or delete it until it's moderated? Sorry to have bothered you.
    No problem at all. It requires Moderation approval if you have an HTML attachment. I can delete this thread if you want me to.
    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.

  5. Default

    Thanks Danny, no need to delete, might help someone else. I was more looking to edit the original post, to let you know I resolved it from other posts I'd read. Peace out!

    HP EFI V4, 388cid Stealth Ram, 1000 CFM 58mm throttle body, Holley Dual Sync Distributor. LS Coil Near Plug, 1 bar MAP, 48 lb/hr Holley EFI injectors, 43 psi

  6. #6
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    Quote Originally Posted by 383_StealthRam View Post
    Thanks Danny, no need to delete, might help someone else.
    That's what I was thinking too. Thanks for the update/resolution.
    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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