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Help! Rb20det tps issue? Won't idle

Kraaken.r32
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Kraaken.r32 Rookie

Kraaken.r32

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Hey guys. Been scouting these forms for months since I got my car last year. I'm in Alberta Canada but this seems to be the best forum for info. 

 

Anyhow, I have a. 1989 r32 gtst with the rb20det, fmic, rb25 turbo, walbro 255, blitz intake and bov delete. It will not idle when warm. The car will stall coming to red lights after the rpm drop almost everytime. I have a brand new tps sensor in the car and I still get code 43 (tps code). So I'm wondering is this my issue? Does anyone have any idea what the voltage is supposed to be going into the tps? I have 5v at the 3 wire plug and 12v at the tps sensor it self. I set the tps to. 0.48 where it should be and still nothing. I watched the voltage go up smoothly with the throttle all the way to wot (car off, ignition on) it reads 4.08v. 

 

My iicv will not help adjusting my idle either.. 

 

Also while I'm revving the car. I'll hold and maintain idle at 3k or 4k whatever I tried it at it sounds like a misfire Is also happening. I have brand new plugs in the car so I'm certain it's not that. It boosted fine last summer with no hesitation or missing, (haven't been able to drive it since because of winter here). 

 

What do you all think it is? Clearly an issue at the tps or something. 

 

Thank you all for the help on this, I hope to have this solved rather quick. I do plan to swap some Toyota echo coil packs in very shortly too, if anyone has some info on wiring that would be appreciated too! 

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GTSBoy Grand Master

GTSBoy

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RB20s do not use the analog output from the TPS for the ECU.  They really only use the closed position switch for the idle position.  The potentiometer on them is for the TCU.  The idle switch should be set so that it changes state just as you start moving the throttle away from closed.  If you bend over the idling engine and you manually move the throttle bellcrank, at the very very first movement of it, the ECU should double pulse the injectors.  If you hear that at that point in the rotation, it is set correctly.  The trick is to set it too high, so you can tell that it is doing it, then adjust it down from there.

You MUST have the IACV working, otherwise it will stall coming to a halt.  Take it off, dismantle it and clean it with solvent.

Kraaken.r32 Rookie

Kraaken.r32

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28 minutes ago, GTSBoy said:

RB20s do not use the analog output from the TPS for the ECU.  They really only use the closed position switch for the idle position.  The potentiometer on them is for the TCU.  The idle switch should be set so that it changes state just as you start moving the throttle away from closed.  If you bend over the idling engine and you manually move the throttle bellcrank, at the very very first movement of it, the ECU should double pulse the injectors.  If you hear that at that point in the rotation, it is set correctly.  The trick is to set it too high, so you can tell that it is doing it, then adjust it down from there.

You MUST have the IACV working, otherwise it will stall coming to a halt.  Take it off, dismantle it and clean it with solvent.

OK so you don't feel like this is a wiring issue? I mean the tps is brand new and as far as I know setting it to 0.48 is all it should need to be done. I did clean my iacv but it won't adjust idle. I'll screw it either way and doesn't affect anything. I unplugged the tps while I did it. 

GTSBoy Grand Master

GTSBoy

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1 hour ago, Kraaken.r32 said:

and as far as I know setting it to 0.48 is all it should need to be done

No, you didn't listen to what I said.  RB20s are not RB25s.  The RB25 uses the analog output of its TPS (That's the potentiometer) for setting the idle point.  And the correct voltage setting for that is ~0.45v.  The RB20 DOES NOT use the potentiometer of the TPS for any function.  The pot is only for the transmission computer.  The RB20 uses the TPS's switch.  A digital switch.  On, off.  There is no 0.45 volts associated with that.  It is a simple click decision.  If you look closely at the TPS you will note that there are two connectors.  One for the ECU and one for the TCU.  In a manual car, the TCU one is not even really connected to anything.

As to whether there is a wiring problem with your IACV....there could be, but that is impossible to internet diagnose.  Dirty/seized up is always far more likely than a wiring problem unless someone clumsy has been buggering around with it.

Slap Rising Star

Slap

Posted
Posted

Have you reset the ecu since putting in the new sensor?
To make sure its not the old code.

What happened to the old one, did it just die?

As gts boy said it might not be switching correctly.

How long has it been doing it?
Throttle body could possibly need a clean.

What got changed before it started this behaviour?

Kraaken.r32 Rookie

Kraaken.r32

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6 hours ago, GTSBoy said:

No, you didn't listen to what I said.  RB20s are not RB25s.  The RB25 uses the analog output of its TPS (That's the potentiometer) for setting the idle point.  And the correct voltage setting for that is ~0.45v.  The RB20 DOES NOT use the potentiometer of the TPS for any function.  The pot is only for the transmission computer.  The RB20 uses the TPS's switch.  A digital switch.  On, off.  There is no 0.45 volts associated with that.  It is a simple click decision.  If you look closely at the TPS you will note that there are two connectors.  One for the ECU and one for the TCU.  In a manual car, the TCU one is not even really connected to anything.

As to whether there is a wiring problem with your IACV....there could be, but that is impossible to internet diagnose.  Dirty/seized up is always far more likely than a wiring problem unless someone clumsy has been buggering around with it.

OK sorry didn't understand. Now I got it. So what you are saying is I should be able to adjust it forward till it idles ok then test? 

Kraaken.r32 Rookie

Kraaken.r32

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2 hours ago, Slap said:

Have you reset the ecu since putting in the new sensor?
To make sure its not the old code.

What happened to the old one, did it just die?

As gts boy said it might not be switching correctly.

How long has it been doing it?
Throttle body could possibly need a clean.

What got changed before it started this behaviour?

I believe it is an old code but I don't know how to reset the ecu. I removed my neg battery cable and let it sit for a minute but didn't help. It has been doing this since I owned my car. About a year. One thing I haven't done is clean the throttle body. Maybe that's next 

Slap Rising Star

Slap

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Posted
I believe it is an old code but I don't know how to reset the ecu. I removed my neg battery cable and let it sit for a minute but didn't help. It has been doing this since I owned my car. About a year. One thing I haven't done is clean the throttle body. Maybe that's next 
You can look it up specific or just wait for my buddy here to correct me.

Negative terminal off - Ignition on - press and hold brake for aprox 3-5 mins. Done.
Turn off key - put terminal on.

The ecu retains some power so by pressing the brake it tries to light the signals and drains the ecu.
Kraaken.r32 Rookie

Kraaken.r32

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1 minute ago, Slap said:

You can look it up specific or just wait for my buddy here to correct me.

Negative terminal off - Ignition on - press and hold brake for aprox 3-5 mins. Done.
Turn off key - put terminal on.

The ecu retains some power so by pressing the brake it tries to light the signals and drains the ecu.

Sounds simple. I'll give it a shot and then pull the codes after work today. Thank you! 

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Kraaken.r32 Rookie

Kraaken.r32

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13 hours ago, Slap said:

You can look it up specific or just wait for my buddy here to correct me.

Negative terminal off - Ignition on - press and hold brake for aprox 3-5 mins. Done.
Turn off key - put terminal on.

The ecu retains some power so by pressing the brake it tries to light the signals and drains the ecu.

Sounds simple. I'll give it a shot and then pull the codes after work today. Thank you! 

Kraaken.r32 Rookie

Kraaken.r32

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So did some diagnosing. Everything is checking out perfect. We had a scan tool to monitor everything and the tps is working, iacv working, the only thing I'm unsure of is the O2 sensor. Also I'm going to coil pack convert the car this weekend so that should solve any misfire I have I believe. But the idle hunt is still there. Now I got it to the point it will idle very well, but when I rev it a couple times the car will then drop the idle to 500 or less and struggle to stay alive. 

Slap Rising Star

Slap

Posted
Posted

[emoji849][emoji51][emoji3166][emoji856]

 

I have had to much negative feed back when i assist with things like this not that all the feed back is bad

. Hopefully someone will chime in b4 the temptation to hypothesis becomes to much!

 

 

Ahh i remember this... and i quote gts boy here as a flash back.

 

"Gents,

When Slap is asking about closed loop, he's talking about closed loop fuelling.  I suspect when Johnny Dose is talking about closed loop (in above posts) he's talking about closed loop idle speed control.  So, talking at cross purposes.

As has been posted before;

At idle (ie, TPS closed, ~0.45v) the ECU is definitely in closed loop idle speed control.

At idle, provided the O2 sensor is warm enough, the ECU will be in closed loop mixture control.  But this often fails and the ECU will just revert to the idle fuelling map.

At idle, the ECU does not change timing based on O2 feedback.

At idle, the ECU adds AND subtracts timing from the base 15° according to its needs for idle speed control, but is aiming to run 15° and control speed with IACV wherever possible.".

 

 

Kraaken.r32 Rookie

Kraaken.r32

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18 hours ago, Slap said:

emoji849.pngemoji51.pngemoji3166.pngemoji856.png

 

I have had to much negative feed back when i assist with things like this not that all the feed back is bad

. Hopefully someone will chime in b4 the temptation to hypothesis becomes to much!

 

 

Ahh i remember this... and i quote gts boy here as a flash back.

 

"Gents,

When Slap is asking about closed loop, he's talking about closed loop fuelling.  I suspect when Johnny Dose is talking about closed loop (in above posts) he's talking about closed loop idle speed control.  So, talking at cross purposes.

As has been posted before;

At idle (ie, TPS closed, ~0.45v) the ECU is definitely in closed loop idle speed control.

At idle, provided the O2 sensor is warm enough, the ECU will be in closed loop mixture control.  But this often fails and the ECU will just revert to the idle fuelling map.

At idle, the ECU does not change timing based on O2 feedback.

At idle, the ECU adds AND subtracts timing from the base 15° according to its needs for idle speed control, but is aiming to run 15° and control speed with IACV wherever possible.".

 

 

15 degrees is the proper timing for the rb20? I heard was 20 degrees? I'm going to retime the car this weekend as well after my coil pack conversion is done. So basically the O2 sensor would have no bearing effect on the idle of my car? I'm horrible when it comes to electrical.. So excuse me if I'm understanding things wrong here. 

 

Thank you for the help

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