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Thread: JDM B20A PK2 VS PH3 Distributor Operation

  1. #1
    DX User B20A1986LXI's Avatar
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    JDM B20A PK2 VS PH3 Distributor Operation

    Hello, this is my second post on 3Geez but I have been lurking here for awhile. I have a JDM B20A Gold Top with a B2K5 MT I have just finished swapping into my 1986 LXI. So far it runs great on the USDM PK2 Prelude ECU with PK2 distributor @ 15 degrees of ignition advance with the timing connector jumped but it doesn't run so great with my JDM 37820-PH3-900 that I purchased from the most Eastern part of Russia on (that's another story). Anyway, with the PH3 ECU installed, and the PK2 distributor left un-touched from its 15 degrees advance setting, It instantly jumps to 20 degrees advance, sets blink code "9" for cylinder sensor and the engine will not rev beyond 4000 rpm. The only information I have been able to find on the web is that the PK2 distributor phase angle may be incorrect for the TDC & Crank angle sensor since the PGMFI ECU & Distributor codes/design do not match. Possibly something about leading vs trailing edges of sensor trigger points in the distributor. (We all know how impossible it is to get the cap & rotor for the PH3 distributors). I have tried retarding and advancing the PK2 distributor to resolve the Cylinder (exhaust cam) sensor blink code 9 fault but it has not helped. (Please note that I have also re-pinned the relevant wires in the PK2 to the 86-87 PH3 ECU ignitor, ignition calibration, and vehicle speed sensor pin locations. This is the JDM PH3 ECU version with the separated FI & IG computers in one box & 2 blink code bulbs.

    Also, if anyone is curious, the PK2 ECU WILL run "okay" with the idle control solenoid found on the 86-87 LXI & JDM 2.0 SI/B20A motor until heavy electrical loads like headlights/brake lights get turned on. The solenoid/PK2 ECU is very slow to respond to increases in engine loads at idle and gets close to stalling. (The PK2 IACV is designed to operate on PWM (to hold the IACV open at varying amounts based on the length of the pulses (it hums vs clicks during operation)) while the 86-87 Accords/Preludes are designed to work either 100% open or closed to smooth the idle with the assistance of the AC boost solenoid & various other open or closed solenoids. I am planning modify a 2000 D16Y8 IACV (that I already happen to have) to fit in the driver side remote Idle air control solenoid position next week and tune it to see if I can get acceptable Idle control under all conditions including A/C on.

    Anyway, to summarize my original question, has anyone been able to get a USDM PK2 distributor to run correctly with a Gold Top version (86-87) PH3 ECU? Or am I going to need to use the PK2 ECU & Distributor together? Thanks for your time.
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  2. #2


    Join Date
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    Re: JDM B20A PK2 VS PH3 Distributor Operation

    I moved your thread because for some reason its not really "on top" with any forums or under "new" post on the left side. Not sure why.
    1988 Lxi owner since August 1995
    336k miles running strong!
    Now running E85.

    Oldblueaccord <<< MY YOUTUBE PAGE!

  3. #3

    Dr_Snooz's Avatar
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    Re: JDM B20A PK2 VS PH3 Distributor Operation

    I know nothing about it really, but since it's giving you a cam sensor code, are you sure the cam sensor isn't faulty? A bad one could sure cause what you describe.
    Dr_Snooz

    "I like to take hammers, and just break stuff, just break stuff." - Beavis


    1989 Honda Accord LX-i Coupe, 240k miles, MT swap, rear disc swap

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  4. #4

    ShiRen's Avatar
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    Re: JDM B20A PK2 VS PH3 Distributor Operation

    My question is, why don't you have a ph3 distributor to try, and why don't you have a pk2 iacv? We don't really know the respective part numbers to tell you much, this isnt as ubiquitous as a p28 or p72. I don't even know what a ph3 is and I am confused why some parts come up for our usdm cars, the usdm cars are typically pj0. The ph3 dizzy, are you talking about the stock a20 pgmfi TEC dizzy? Because you can easily get a cap and rotor for that, parts stores will tell you the parts fit a TEC or hitachi, and its always TEC for pgmfi. I have only been able to find out that pk2 is from a 3rd gen prelude.
    This is really intriguing to me and I wish we could help more, but jdm parts for these cars are really obscure. I will tell you this: If the pk2 is from the prelude and the pj0 is from the accord, the pk2 is the superior part, if I were you I would just want to get the pk2 iacv working. I say that because the pk2 uses a better distributor than what is found on the pgmfi a20, it should make more power and make the car run smoother. In the meantime, I would suggest reducing the idle load. AC is going to be your biggest load and you can't do much about it, but leds would be a big step, next would be new radiator fans.

  5. #5
    DX User B20A1986LXI's Avatar
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    Re: JDM B20A PK2 VS PH3 Distributor Operation

    My question is, why don't you have a ph3 distributor to try?:
    (I do have the PH3 Distributor body and internals (30100-PH3-016) but the Cap+Rotor are missing and IMPOSSIBLE to order as they were exclusive to the forward leaning JDM B20A (2nd Gen Prelude & 3rd Gen Accord/Vigor, (Not the rearward leaning 3rd Gen Prelude B20A5 Engine). This is why I have fitted the PK2 distributor to my B20A. It shares the same trigger coil(s) design as the PH3, 24 teeth. A few other B20A owners have installed the PK2 distributor as well in the past successfully (looking at you Carrot Man) but I don't know if a PH3 ECU was used in place of the Prelude PK2).

    I have run shielded wire for the cylinder position sensor back to ECU pins C1&C2 and the coil resistance values for the CYL, Crank, & TDC sensors all fall within the 700-1000 OHMs range. The car seems to run and drive perfectly fine with the PK2 distributor & ECU but not when I swap the PH3 ECU in and re-pin it as needed. (The 86-87 Gold top ECUs have a very unique pin out while the 88-89 ECUs are essentially the same as the USDM 88-89 PK2 preludes).

    And why don't you have a pk2 iacv?:
    (The 86-87 B20A "Gold Top" Engines used the same idle controls as the 86-87 PJ0 (USDM) accord with the remote mounted IAC solenoid (36180-PH3-003) while the 88-89 JDM "Black Top" B20A, 88-89 USDM A20A3 Accord and 3rd Gen USDM Preludes with the B20A5 engines used the (36450-PK2-023) intake manifold mounted IACV that is Pulse width modulation controlled). My 86 B20A is fitted with my original A20A3's single stage manifold that does not have a way to mount the PK2 style IACV to it. To get the 88-89 style A20A3/B20A manifold & IACV would cost me about $300 USD & many additional hours of cleaning, installation of the dual stage runner vacuum control system + fitment time.)

    Essentially, the PH3 ECU is better suited to my B20A "Gold Top" as it currently sits in my 86 LXI and is the historically "Correct" ECU for the engine. I can use the PK2 with its matching distributor but I need to work on the Idle control system and see if anything else comes up during the driving tests. I would just like to know if anyone has been able to get this ECU/Distributor combo to work correctly.
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  6. #6

    ShiRen's Avatar
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    Re: JDM B20A PK2 VS PH3 Distributor Operation

    Its very likely that anyone else on this forum just lived with the iacv issues...
    What about using a b20a5 intake?

    Here is something we can try... go buy a solid state relay, or maybe even a regular relay for the time being. Connect it to the pwm signal to the iacv and use it to turn on the iacv. Make a circuit from the battery, to the relay, to the iacv. This will convert the pwm to battery volatge, I suspect it to work at 100% load, but as far as turning off, I don't know how low of a signal the ecu puts out... surely it goes to 0v while driving, or low enough the relay stops responding. It will help if you have an oscilloscope, if you don't I can recommend a cheap digital one. Solid state relay is preferred, it will cause less noise and uses little current, it will switch at the speed of the pwm and so will the output, but I don't imagine the iacv will move that fast. Regular relay might burn out if the pwm is slow enough for it to switch constantly. If the pwm is a problem for either relay we can add a low pass filter to the pwm signal so the relay only provides the peak voltage, if the peak voltage is always 12v though then a relay might not even be necessary. I don't know what resistor/diode or cap you would need for the low pass filter though, but we can figure it out, it may be as simple as a small cap, like this. If we know the car behaves correctly when the iacv only receives 0v or 12v then that is a big step forward.
    Last edited by ShiRen; 04-11-2022 at 10:07 AM.

  7. #7


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    Re: JDM B20A PK2 VS PH3 Distributor Operation

    Quote Originally Posted by B20A1986LXI View Post
    Hello, this is my second post on 3Geez but I have been lurking here for awhile. I have a JDM B20A Gold Top with a B2K5 MT I have just finished swapping into my 1986 LXI. So far it runs great on the USDM PK2 Prelude ECU with PK2 distributor @ 15 degrees of ignition advance with the timing connector jumped but it doesn't run so great with my JDM 37820-PH3-900 that I purchased from the most Eastern part of Russia on (that's another story). Anyway, with the PH3 ECU installed, and the PK2 distributor left un-touched from its 15 degrees advance setting, It instantly jumps to 20 degrees advance, sets blink code "9" for cylinder sensor and the engine will not rev beyond 4000 rpm. The only information I have been able to find on the web is that the PK2 distributor phase angle may be incorrect for the TDC & Crank angle sensor since the PGMFI ECU & Distributor codes/design do not match. Possibly something about leading vs trailing edges of sensor trigger points in the distributor. (We all know how impossible it is to get the cap & rotor for the PH3 distributors). I have tried retarding and advancing the PK2 distributor to resolve the Cylinder (exhaust cam) sensor blink code 9 fault but it has not helped. (Please note that I have also re-pinned the relevant wires in the PK2 to the 86-87 PH3 ECU ignitor, ignition calibration, and vehicle speed sensor pin locations. This is the JDM PH3 ECU version with the separated FI & IG computers in one box & 2 blink code bulbs.

    Also, if anyone is curious, the PK2 ECU WILL run "okay" with the idle control solenoid found on the 86-87 LXI & JDM 2.0 SI/B20A motor until heavy electrical loads like headlights/brake lights get turned on. The solenoid/PK2 ECU is very slow to respond to increases in engine loads at idle and gets close to stalling. (The PK2 IACV is designed to operate on PWM (to hold the IACV open at varying amounts based on the length of the pulses (it hums vs clicks during operation)) while the 86-87 Accords/Preludes are designed to work either 100% open or closed to smooth the idle with the assistance of the AC boost solenoid & various other open or closed solenoids. I am planning modify a 2000 D16Y8 IACV (that I already happen to have) to fit in the driver side remote Idle air control solenoid position next week and tune it to see if I can get acceptable Idle control under all conditions including A/C on.

    Anyway, to summarize my original question, has anyone been able to get a USDM PK2 distributor to run correctly with a Gold Top version (86-87) PH3 ECU? Or am I going to need to use the PK2 ECU & Distributor together? Thanks for your time.
    if you think the TDC or the crank angle are off you might swap the wires and see if that gives you the signal you need. I would imagine you tach reading off as well?
    1988 Lxi owner since August 1995
    336k miles running strong!
    Now running E85.

    Oldblueaccord <<< MY YOUTUBE PAGE!

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