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

2K views 7 replies 5 participants last post by  SuprasEdge 
#1 ·
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 ·
You seem to know what you are doing. I assume you pulled a fuse or the neg. batt. cable to clear the code.
 
#5 ·
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.
 
#6 ·
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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#7 ·
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!
 
#8 ·
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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