84 motor into 85 main snag fix(knock sensor issue)

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  1. #1
    Junior Member SuprasEdge's Avatar
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    84 motor into 85 main snag fix(knock sensor issue)

    At the beginning of 2017 I decided to finish my 84 5m build and replace the tired motor in my 85. Everything went pretty smoothly. I had many parts from my previous supras to replace the old broken parts that came off. Had a cracked front engine cover that I repaired and is holding strong. And then I had a scare when started the motor. It sounded like a dying diesel engine because I chose not to prime my lash adjusters. Turns out 4 years sitting will drain stored oil. Any way the adjusters eventually pumped up and quieted down. Then the check engine light came on.. anybody who owns these knows it takes a lot for the CEL to come on so I checked the code. Code 52-the knock sensor circuit open code. I tried several things. I attached a ground strap to the sensor, didn't work. I grounded the wire, didn't work. So after a day or so of researching i finally figured it out.. well after I made sure the wire to the ECU wasn't broken.. I took an intake manifold to cylinder head bolt, welded an m12x1.25 nut to it, I double checked electrical continuity and fittament. Using a crow foot wrench and socket extension I installed it on the manifold between cylinders 2 and 3(only place it would fit) I had to modify the connector so that it wouldnt be putting pressure on itself against the manifold runner. I torqued it to about 17.3ft/lbs on my torque wrench but doing the math it comes out to about 15.66ft/lbs on the bolt which is in spec. (16ft/lbs +or-1lb) and ta daaaaa no more CEL, the motor was able to go into closed loop. The ECU relearn kinda freaked me out because the idle speed wasn't constant and the engine would stall when stopping at intersections but when I drove it to work and about halfway there the idle started to hold and the engine will now catch itself when coming to a stop so I'm pretty sure its just 5he ECU relearning. Now here are some pics!

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  3. #2
    CelicaSupra.com Member
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    Nice pictures,, Great solution to the knock sensor.

  4. #3
    CelicaSupra.com Member supkar's Avatar
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    You seem to know what you are doing. I assume you pulled a fuse or the neg. batt. cable to clear the code.
    83-Red P-type , 6M,. LJM strut-bar, RC intake,Thorley header,Tenzo 17" wheels, cross-drilled rotors, Eibach springs, KYB shocks, 85 hatch and int., 82 header panel=Frankenkar

    87 4 Runner, White, 22RE, 302K on original motor, still strong

    "This car is so loud , I heard you before I saw you!" said the nice policeman. Hidden Content

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  6. #4
    Junior Member SuprasEdge's Avatar
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    Quote Originally Posted by supkar View Post
    You seem to know what you are doing. I assume you pulled a fuse or the neg. batt. cable to clear the code.
    Yeah, the negative terminal works everytime!

  7. #5
    CelicaSupra.com Member 4SFED's Avatar
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    Did you swap the '85 TPS onto the '84 motor you put in your '85? I assume that since you put the knock sensor in that you are using the '85 harness and ecu, not the '84. The '85 TPS is a potentiometer-type vs. a switch-type in the '84.
    Dave Harrison

    current lineup and year acquired:

    '85 white Mark2 7mgte 5sp 1990
    '85 white Mark2 7mgte Auto 2009
    '84 maroon Mark2 6mge 5sp 2013
    '85 black Mark2 2jzge 5sp 2015
    '86 SDR Mark2 7mgte 5sp 2016

    Hidden Content Originally Posted by cheappower82 Hidden Content
    Guess you have the magic touch; touch mine please?!

  8. #6
    Junior Member SuprasEdge's Avatar
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    Yeah, I used the 85s intake manifold because it was in better condition and I had recently replaced all the injector seals so I didn't want to move them around too much. Plus the EGR and stuf already had the proper vacuum line routing so that did take a little strain out of installation. I left all the sensors and switches on the manifold for the same reason.

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  9. #7
    CelicaSupra.com Member RedP85's Avatar
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    great idea to mount the K Sensor.
    I never had issues with mounting torque, and i know i'm too generous on that aspect.
    So i'm not the only one that thinks the 5M ecu does some learning!
    -Jocelyn,
    P85-6MGE SDR(HKS kit c/w IC and F-Con in a box) 225KKm, NAL seats, 2.5 Brullen, ACT clutch, LJM, SS lines, Trip Computer. EuroH4
    P85-5MGE SDR had 439KKm (for 17 years my daily driver, RIP...), 2002 E39 ///M5 LMB Hidden Content
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  10. #8
    Junior Member SuprasEdge's Avatar
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    Quote Originally Posted by RedP85 View Post
    great idea to mount the K Sensor.
    I never had issues with mounting torque, and i know i'm too generous on that aspect.
    So i'm not the only one that thinks the 5M ecu does some learning!
    Oh yeah, it had to relearn a few things. I had to torque the bolt because it was one of the intake manifold to cylinder head mounting bolts. My thought is if Im going through the trouble of making a good mount I might as well put it in a good spot

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