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Thread: 2D Pro-Jection stumble off idle/at cruise.

  1. #1

    Default 2D Pro-Jection stumble off idle/at cruise.

    After reading lots of posts on the forum and elsewhere, speaking with Woody @ Holley Technical, bringing the car to the guy who did the engine swap to ensure timing was correct and vacuum advance functioning correctly, etc. I’m no closer to resolving this issue than I was before. If anything, I’m probably more confused so I'm hoping for resolution/clarity.

    BASELINE INFORMATION: Rover 4.2 liter V8 (think old Buick Aluminum 215). Possible mild cam or stock cam offset a few degrees (builder doesn’t remember) in a 1970 MGB-GT with 5 speed manual transmission.

    Edelbrock Performer Manifold
    2BBL Projection Throttle body that started life with an analogue ECU, since upgraded to 2D ECU (534-55), Closed Loop. (This all replaced a 390cfm Holley Carb many, many years ago.)
    New style injectors, confirmed in good operating condition.
    TPS functions as expected, smooth voltage changes throughout range to WOT.
    New, tested, TPS currently installed. (Yes, I threw a part at it.)
    TPS is set at .45 volts per Woody’s recommendation vs .63-.65 factory advised. This was done as the first step to rectify the issue. (It didn’t help.)
    Potentiometers were set using an MSD Rich/Lean indicator per Holley Instruction manual.
    No vacuum leaks that I can find. Hoses are new and visually look in good shape (there only two, vacuum advance & PCV), spraying TB, etc., with starting fluid shows no change in idle.

    ISSUE: As stated above and like others, stumble off idle and at cruise, 1,200 – 1,400-ish RPM. Potentiometer adjustments won’t resolve, some changes better, most worse. Like others I can “drive though it” via throttle input. Rich/Lean indicator shows lean (?) if memory serves upon occurrence.

    Can’t recall if eliminating the O2 sensor made a difference. I know I did this and assume it didn’t change anything since it's plugged back in now.
    No audible exhaust leaks. Headers are tight to heads. Operated fine for years throughout the ECU and injector changes noted above. This started last spring (?), maybe longer ago, but the cure was sidelined due to Covid-19 and affected career change. If I recall correctly, I found a bad vacuum advance, torn diaphragm, at the time of the performance change and thought my issue would be resolved by simply replacing it. That’s when I started down possibly misguided paths to find a solution.

  2. #2

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    I used to have the analog Pro-Jection system back in the early '90s...brings back memories.

    If it was me, at this point I'd start with the basics. New plugs, wires, rotor & cap. Your lean spike can very well be a cylinder misfiring. Andrew

  3. #3

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    Thanks Andrew. Cap & rotor were replaced previously. Inspected again last night, all looks good. I inspected the wires using the age old practice of spraying a fine water mist over the wires at night to see any arching. None. So I can check the wires off the list. Plugs were changed back when too. Electronic ignition checks out via its on-board diagnostic LED.

  4. #4

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    Quote Originally Posted by mgcyclo View Post
    Thanks Andrew. Cap & rotor were replaced previously. Inspected again last night, all looks good. I inspected the wires using the age old practice of spraying a fine water mist over the wires at night to see any arching. None. So I can check the wires off the list. Plugs were changed back when too. Electronic ignition checks out via its on-board diagnostic LED.
    Since we are checking the basics, I wouldn't assume anything. I would pull the plugs and see what they look like. There might be some clues there.

    Andrew
    Instagram: @projectgattago
    Offering remote Holley EFI tuning.
    I deliver what EFI promises.
    Please get in touch if I can be of service.

  5. #5
    Join Date
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    Location
    Connecticut
    Posts
    28,521

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    My first aftermarket EFI system was a Holley Pro-Jection 4D. I or anyone else I knew, never got those tuning knobs set well. The engine always ran too rich or too lean.
    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, 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/3-core Frostbite 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, LenTech Strip Terminator wide-ratio AOD/3000 RPM converter, B&M Hammer shifter, 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.

  6. #6

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    Quote Originally Posted by Danny Cabral
    "I or anyone else I knew, never got those tuning knobs set well. The engine always ran too rich or too lean."
    I tend to agree, but for years the system never lent itself to a driveability concern such as the stutter I'm experiencing. If rich or lean it still drove well. Now there's this stutter that I initially thought was caused by a bad vacuum advance canister which would have caused both a vacuum and timing issue. I'm going to start by resetting the TPS to .63 per the instructions and see what happens. I welcome anyone's feedback/experience.

  7. #7
    Join Date
    Dec 2009
    Location
    Connecticut
    Posts
    28,521

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    Quote Originally Posted by mgcyclo View Post
    I'm going to start by resetting the TPS to .63 per the instructions and see what happens.
    Yes, that's very important for proper Pro-Jection 2D operation.
    https://forums.holley.com/showthread...&p=932#post932 (Related Forum Thread)
    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, 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/3-core Frostbite 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, LenTech Strip Terminator wide-ratio AOD/3000 RPM converter, B&M Hammer shifter, 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.

  8. #8

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    Thank you Danny. Step 2, page 7 of the instructions provided states, "If installed, remove the oxygen sensor harness from the digital ECU by unplugging the harness from the rear of the ECU." But the instructions never state when to plug it back in.

    Two pages later they highly recommend using a Rich/Lean indicator, which I have. It needs the O2 sensor to operate so therefore can't be plugged into the ECU at the same time. The instructions refer to use of the Rich/Lean indicator for setting the Main, Idle & High RPM.

    I assume once those are set the O2 sensor can be plugged back in and then the Choke setting can be set with it operating. NOTE Both the Choke & Accel settings are "seat of the pants"/experiential guidelines, i.e. no reference to Rich/Lean indicator.

    UPDATE 5/1: I simply set the TPS to .63 volts. I didn't change anything else. Due to an afternoon commitment I only had time to take the car for short 4 mile drive around the neighborhood this morning and it seems that there is a noticeable improvement. A longer test drive is needed but maybe I'm on the right track.
    Last edited by mgcyclo; 05-01-2021 at 10:35 AM.

  9. #9

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    Got out for my usual 30 mile-ish test drive loop yesterday to test the reset of the TPS. That subtle adjustment seems to have resolved my annoying stutter that I was experiencing off-idle and at cruise. The fuel map probably isn't ideal and it's idling about 200 RPM too high, but I'm going to try and ignore that for now and just enjoy it. Thoughts?

    ALSO, about 3/4 the way into the drive, after playing with Mercedes E35 AMG, the fuel delivery cut out. This has happened before. It occurs randomly and will restart sometimes while I'm still coasting if I shift to neutral and start with the key. This time I had stop on the side of the road for a few seconds, get my bearings and hit the key.

    Way back when I first experienced this I found a loose electrical post on the fuel pump, thought that was it. Would a relay to the pump help? The ECU is powered via relay, but not the pump.

  10. #10

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    After sleeping on things for a few days, I decided that I couldn't live with the high idle. So I took the car out to see if I could or not. I just can't. The thing is (was) idling at 1300 RPM and though driveability was much improved, it would still "load up" if tooling around or sitting at a light too long.

    My plan was to set the mechanical idle and then reset the TPS to the .63V noted two posts above. Instead I just set the mechanical and then took the car for a drive to see what that alone did. CAR DRIVES GREAT! The results are, I'm not going to touch a thing from here on.

    For curiosity, I wanted to see where the TPS ended up after setting the mechanical idle. It settled at .54V.

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