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Discussion Starter #21
Stock mk2 Supra 5spd is a 4.3 rear, with w58, 25.6 inch diameter tires as I recall. Stock mk3 Supra Turbo is 3.9 or 3.73 depending on year, r154 of course, and tires 26inch something diameter.

Are you sure your rear is an 8? My 03 Tacoma has the same 7.5R&P the mk2 does, which is great because I have a couple LSDs laying around. If you do have an 8, you should be able to run the mk3 Supra LSD, which is a really strong unit and not too hard to find. Swapping gear sets is always challenging in diffs btw.

That's awesome you fixed your fuel setup, thats much better and safer for sure.

Oil leaks will appear everywhere if your crankcase is pressurized, I wouldn't worry about the ones you had, just the ones you have. But the leak could easily have come from the valve covers or cam shaft housings where they connect to the head. There is a metal gasket in there that is notorious for leaking after people take them apart, if they havn't cleaned up their surfaces just right or used a new gasket. Most of us add a little spray to those gaskets for extra insurance.

Yeah just take that ISCV out and check out its plunger and what the inside of the hole looks like. Could just be the inside is carboned up so bad the plunger was seized. Thats uncommon, but who knows. Bench test it and you will know if the problem is in the mounting, the valve itself or the wiring.
My rear end is definitely an 8 incher, they only came in the 4 speed 22r trucks. I do have a spare complete 7.5 rear end laying around i could swap in that has 3.73 gears. I think ill weld that up to get me burning tires. I would definitely be interested in figuring out how to get a diff from you, if thats on the table. Wether its a 7.5 lsd or an 8, i can use either.
 

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Oh I barely have enough spare LSDs for my own uses, wasn't offering lol.

I wouldn't downgrade to the 7.5. The mk3 Supra pumpkins/lsds are probably easier to find at this point and way stronger. Also it's the same diff R&P size that the is300 and FRS uses, and you can pickup IS diffs with LSD for cheap all day long right now and that's a really nice Torsen unit in that.

The 7.5 is a strong enough diff if you throw a Trutrak into it, but the other LSD options for it get flaky around 300rwhp.
 

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Discussion Starter #24
I need help figuring out my idle. It starts and runs at 3000rpm or so, thats my best guess as i don't have tach. It drops a few 100 rpm over a couple minutes. It does this no matter if its cold or warm. When its warm it almost seems to start even higher. It also does it every start. I can shut it off, and restart it immediatly and if it had lowered idle before, it will startup with high idle again. On my 20 minute drive to town, by the time i get there it will have a normal idle, somtimes.... I took my iscv off and dissambled it. it was very clean, fully functional by the manual. It tested good both on the bench and on the car. It has a steady power source in ignition switch on position and running. The resistance test was perfect too. Then when i put it back on i set it fully closed, it started, idled properly and dropped down to a reasonable rpm quickly. The next start it was up to the 3k rpm again and doing the same shit as before!!!
I have done every test in the tsrm. The tps is tested and adjusted. The temp sensor is good and tested. The icsv is good and tested. The afm and iat all test out good too. Also tested the fuel pressure. I ran the engine and sprayed carb cleaner at all holes/ports/inlets. No change to how it runs at all. No vacuum leaks. The only way i can get the idle down is the pinch the iscv tube, or wait for it to randomly lower enough by itself. I am wondering if i need reroute the hose from before the turbo to after the turbo.
What is going on?!?!?!
 

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I don't know ANYTHING about turbo systems at all and I don't know how people have traditionally plumbed the ISCVs on their systems, but that flow path is just the equivalent of adjusting the throttle stop on a carb to let a little flow around the closed throttle blade.

When I bought my wife's 84 the ISCV wasn't working so I did the same troubleshooting you are doing. With about the same results. It turned out to be the coil drivers in the ECU were bad. I put in another ECU and up she came.

The give away for me was the sound of the valve opening when you shut the motor down. When you turn the ignition switch off, the ECU steps the ISCV fully open so that the next time the motor is turned on it will definitely have enough air to start with the throttle fully closed. You can actually hear the valve stepping open when you turn the ignition off. If it isn't doing this it's probably an ECU failure. It could be intermittent initially if a drive transistor is just getting marginal.

You can hear the ISCV stepping fully open at 0:10 minutes in the video

I can't hear the ISCV stepping during idle control because I don't think it steps enough when it's fine tuning. During shutdown the drive assumes the valve is fully closed so it drive IIRC 255 steps. I assume the valve is clutched so the sound is possibly the clutch ratcheting.

It sounds like you've got it covered already, but the screw adjust for the mechanical throttle stop is not and should not be used for an idle speed control because the ECU will fight the speed and try to control on it's own. It's real job is to ensure that the blade is at the correct position during idle so that the TPS contacts are shut. If the throttle stop is mis-adjusted the contacts on the TPS are open signaling the ECU that you have your foot on the throttle and it should not try to adjust engine speed on it's own. I forget which lines at the ECU connector are the TPS idle signal but you can measure right there whether or not the TPS thinks you are idling or not.

I don't think that the Cold Start Injector is causing issues. It turns on when it's own water temperature sensor is below some temperature and it turns the the one injector on for maybe 1 or 2 seconds. If it's leaking it could cause misleading symptoms, but you pinching the Idle Speed hose shut and having an immediate effect is pretty conclusive.

I'd see if I could find another ECU. Make sure it matches the engine year because they changed how the TPS sensor worked at some point. Early ones had one on/off contact to signal idle speed and then 3 or 4 on/off contacts that sent a binary code to the ecu indicating throttle position. Later TPS sensors had one on/off contact to signal idle speed and then a variable resistor that indicated the throttle position. I don't know if the connectors on the wiring connectors on the ECU are different or not (probably not) or what on earth weird symptoms you would get with a TPS/ECU/Wiring mismatch.

Dale

p.s. I'd hire the models, but the Canadian border guards would stop you when you told them you were up here to work. What's your job? Exotic Entertainer sir. Uh huh!, step out of the awesome truck and prepare for a cavity search!
 

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Since this is a swap do you have it wired correctly? The accessory connector needs to be wired correctly so there is power to the ECU after ignition off so the ECU can park the stepper motor. You should hear the stepper motor clicking after you turn the key off. Stepper motors don't have a position sensor so they don't know where they are at. For instance if the ECU has the motor 50 steps open its supposed to move it 50 steps back so it starts at zero again. If it shutoff off at 50 then it will start at 50 and try and go open more from there.
 

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Since this is a swap do you have it wired correctly? The accessory connector needs to be wired correctly so there is power to the ECU after ignition off so the ECU can park the stepper motor. You should hear the stepper motor clicking after you turn the key off. Stepper motors don't have a position sensor so they don't know where they are at. For instance if the ECU has the motor 50 steps open its supposed to move it 50 steps back so it starts at zero again. If it shutoff off at 50 then it will start at 50 and try and go open more from there.
Exactly right. If it think's it's starting wide open, but was in fact almost shut when you turned the engine off, who knows what the ECU programming will do when the motor is started and then tries to control.

The software could just step the ISCV until the motor speed is right, or it could estimate by looking at engine speed and close a predetermined amount it before it tries to fine tune the speed. It could respond in any sort of not logical fashion. I hate software.

That is a very logical point.
 

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Discussion Starter #28
I really appreciate all the help guys.
Supraz, it sounds like i may have partially failing drivers in the ecu. It makes the right noises when i shut it of though... and it seems to be operating just not getting the right idle speed, sometimes. If anyone has a loaner ecu for a 1984 supra that would be sweet.
Silver, i double checked the wiring and everything checks out, also i can hear the iscv operating after shut off.
I wonder if using the o2 signal from the innovate gauge could cause this bs... Or maybe the afm being turned a few clicks, im convinced the afm was adjusted before i got it because it had new sealant on it. Could i roll it back to stock?
 

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The only way the AFM is affecting this issue is if the spring is really cranked tight on it, and the flapper isn't able to open at all at idle anymore. You can take your air filter off and just stare at the AFM while its idling to tell.

Yeah SilverMk2 has it I think, sounds like either you have a wiring problem. I don't think I've ever heard the ISCV make a noise in my life, can't see why the OEM ecu would try and run it after the engine stops running.
 

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Yeah SilverMk2 has it I think, sounds like either you have a wiring problem. I don't think I've ever heard the ISCV make a noise in my life, can't see why the OEM ecu would try and run it after the engine stops running.
Seamus, it really does make a clattering sound after you shut the motor off. It is listed as a troubleshooting step:

TSRM Page FI-60

SilverMk2 correctly described the reason for this. The ISCV does not have a sensor to determine where it is. It depends on the ISCV being in a known position when the engine starts and the ECU counts steps to shut it down to a normal idle speed. I assume that the reason that it is driven fully open rather than fully closed is so there is adequate airflow through the throttle body when the engine is started and one has one's foot off the throttle to have it in the idle position. The stepper very quickly steps down on turn on so the engine speed doesn't race excessively.
It does seem odd that the ISCV is not initialized when the motor is turned on and cranked, but I guess there may not be enough time to ensure the motor starts on the first turn of the key.

Dale
 
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