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Thread: Is this TPS Noise (possibly EMI) worth chasing?

  1. Default Is this TPS Noise (possibly EMI) worth chasing?

    Hi all, I know there are some posts/articles out there on how to isolate/address EMI issues (with mostly Sniper, self contained units) but mines a Stealth Ram with the GM TPI (early style, Weather-Pack not Metri-Pack connector) mounted on the 58mm Accel Throttle Body.

    My question is about TPS %, and the fact that while idling it reads 0% all the time on the LCD display, and on the laptop Online dash/monitors however when I datalog just sitting at IDLE it shows about .25%, or basically not enough to flip to 1% that would indicate any TPS input to the ECU.

    Included a screenshot of the datalog at IDLE, so should I expect that the TPS% while engine is running be dead on 0% just like it is with KEY ON ENGINE OFF? In other words, could that minuscule .25% just be engine vibration and NOT anything to do with EMI?

    If it's EMI, would a valid test be to simply disconnect the TPS and if the .25% drops to 0% then I know it's the TPS generating that signal? Conversely if the .25% is still being seen by the ECU/Live/Datalog then can I assume it's EMI induced to the wiring?

    NOTE: TPS has been replaced 2x with ACDELCO OEM part. Also, I've had issues with the TPS fluctuating from 0-1% at times, and (using Danny's suggestion) after doing a TPS Auto-Set backed off the IDLE SET SCREW on the TB about 1/4 turn to eliminate that. The TPI throttle body return spring is not easily serviceable, and not conducive to adding a secondary carb style spring anywhere.

    I also would note my TPS RoC channel is never showing active which I included in the LOG screen shot.

    Any and all input is appreciated, and I would LOVE to see someone else's live/online LOG of TPS with ENGINE IDLING to see if it stays dead on 0.00% all the time or if a little signal is generating from just engine running/vibration. Thanks for your time!


    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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    Subscribed. Mine does the exact same thing.

  3. #3

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    Mine stays flat 0 with an MSD Pro Billet/6AL and my TPS wiring goes just under distributor/spark plug wires. But I have my engine grounded from both heads and block and run good plug wires.


  4. #4

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    Going to try grounding the TB. I’ve heard grumblings of DBW TBs with plastic intakes having noisy signals until grounded. I’m DBC, but it’s worth a shot. Two alligator clips and a piece of wire. I’ll keep you posted.

    UPDATE: Ran the car last night with no TPS oscillation (and no ground wire). Intermittent issue.

  5. #5
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    Quote Originally Posted by Holley Commander 950 Pro EFI Tuning Manual
    TPS Noise Value: This value corresponds to how much of a throttle change needs to be made before the ECU detects it as having changed and not just electrical “noise” having caused a sensor change. Numbers of 1 or 2 will work well.
    Some TPS sensors are worse than others. OEM (or high quality replacement) TPS sensors seem to be better, and old sensors were worse. Also, electrical noise sometimes happens when something else turns "on". We had this discussion a very long time ago on another forum, in reference to the older Commander 950 Pro EFI system. The C950 EFI had a parameter called TPS Noise Value, noted above.

    Quote Originally Posted by Holley Terminator/HP/Dominator EFI Tuning Manual
    AE vs TPS RoC Blanking: This is the threshold of movement/Rate of Change (RoC) below which fuel is not added due to signal “noise”. For a TPS, this might be vibration, or “very slow” movement of the throttle during which you would not want added fuel. The default values are moderately conservative and should work on most applications. However, some applications with large throttle bodies might prefer to use a lower AE vs. TPS RoC Blanking value. It's recommended to be very cautious when changing these values, as too low of a value will invoke unwanted added TPS vs AE fuel, causing the engine to run sporadically, adding extra fuel when it is not needed. When lowering the value, it is beneficial to look at the Data Monitor and/or Datalogs at the “TPS RoC” values, and see if there is unwanted activity with either.
    The AE vs TPS RoC Blanking value seems to be the same aforementioned parameter.
    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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    When you are dealing with whole numbers, 0.25% gets rounded to 0% in data, and if you saw 0.51%, data probably reads 1%. I think you're splitting hairs. A little bit of noise showing 0.2% is hardly worth chasing.

    Grounding the throttle body itself is unlikely to achieving anything, since the circuitry doesn't touch the alloy of the throttle body. Gary
    Regards, Gary

  7. #7
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    Quote Originally Posted by Gaz64 View Post
    When you are dealing with whole numbers, 0.25% gets rounded to 0% in data, and if you saw 0.51%, data probably reads 1%. I think you're splitting hairs. A little bit of noise showing 0.2% is hardly worth chasing.
    I had the same thought, but wasn't sure.

    Grounding the throttle body itself is unlikely to achieving anything, since the circuitry doesn't touch the alloy of the throttle body. Gary
    I've seen an oval shaped air cleaner cause EMI/RFI noise that wasn't touching anything. Remove it and it's gone; reinstall it and it's back (like an antenna's reception of radiated noise). But this is a TPS, so I don't know.
    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.

  8. #8
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    Thanks for your very valued input Danny. Hope the others in this thread take this onboard. Gary
    Regards, Gary

  9. Default

    Thanks for the replies all. For what it's worth, I replaced the TPS (with a new ACDELCO part) again, this is the third one now. That seems to have made the minuscule signal (< 1%) go away. Now I'm getting fully zeroed TPS % in the live Strip Chart as well as in datalogs.

    What I did learn is that it was definitely not EMI because I could get that jittery signal from the Strip Chart on the TPS without even starting the engine. Given this is (what Danny notes) one of the earliest type of TPS designs (going back to the '80s TBI/TPI engines) it's just likely they are inherently flawed electro-mechanical sensors. If I ever upgrade my throttle body to a later style (than '85-'88 TPI), I can probably use the later TPS that goes directly over the end of the throttle shaft, instead of the little lever actuation.

    Oh well, at least while messing with this I finally did the B20 EST out 12V harness update so my Holley Dual Sync cam/crank sensors are getting clean 12V power from ECU and not the old original (pink/black) ECM IGN feed.

    I do have a follow up question about the LOOSE 18 AWG black ground wire in the Holley Stealth Ram/TPI harness. Right now it goes to the back of the left cylinder head. However it does share the bolt and (separate) ring terminal from the LEFT BANK Coil Near Plug Harness. Is that a problem, and should that ECU ground NOT be tied to the same location as either of the CNP harness cylinder head grounds? The LEFT/RIGHT CNP sub-harness grounds are tied to the back of their respective LEFT/RIGHT cylinder heads.

    I have the main battery ground (2 AWG) to left front of engine (ALT bracket to cylinder head bolt), and there is also a 6 AWG ground from alternator case back to battery. Should I move the LOOSE ECU Ground 18 AWG from back of the left cylinder head to the front and on the same bolt with the 2 AWG battery cable? Thanks for the help.

    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

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