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Zero Voltage at Idle Position Switch and Bad Idle

Pasta_Ricer

Probationary Member
27
2
Nov 2, 2021
Zanjan, Asia
Hi everyone!

So, I have '91 Galant GTI-16V which I recently got and I've been battling some wiring and mechanical issues since I got it. One of my main problems is my weird idle which I'm in the process of fixing (cleaned the horribly dirty IAC stepper motor, cleaned the throttle body, adjusted the throttle cable, and adjusted the TPS to 0.63V).
My main concern is the IPS. The connector had broken off and the previous owner had just twisted the wire from the harness to a piece of wire that was wrapped around the late switch's terminal. As an electronics engineer, this made me cringe big time. I soldered the wire on the IPS and tried to test the voltage on the wire and well, I get nothing. 0.001V which is basically down in the noise. I get the same when off and even when on.
It's even the same when the harness isn't even connected to the switch so it rules out the switch being shorted to the ground.
I also get bad idling when I turn on the AC or sometimes when suddenly engaging the clutch and lifting the throttle.

Since the car has two sensors to check for the closed position of the throttle body, is this normal?
Does the ECU only check the IPS by applying a voltage to it occasionally when you get off the throttle?
Is it used in case the TPS gives erroneous values?

I appreciate any info regarding the workings of the IPS as there isn't a ton of info.

Thanks in advance <3
 

steve

DSM Wiseman
14,865
1,721
Feb 3, 2002
Boulder, Colorado
So, unless your running DSMLink the TPS voltage for a 1G should be 0.5v. The 0.65v that people toss out is DSMLink specific.

The IPS works by pulling the voltage from the ECU down to ground. Make sure that your repairs allow the switch to have continuity to ground when the throttle is closed and is open when the throttle starts opening. Then check the signal from the ECU, it should have at least 5v and more likely 12v pullup when the ECU is on and the wire is disconnected from the IPS. When connected the voltage should be pulled down close to 0v when the throttle is closed and back up to whatever the pull-up voltage was when open.

Without a working IPS the ECU does not know to manage the idle speed, to emulate a dashpot when the throttle is open, or to cut the injectors off on when you close the throttle and are decelerating.

If you don't see a pullup voltage on the IPS line from the ECU make sure your ECU matches the year of your Galant. It should also be inspected to make sure there isn't any capacitor leakage.
 

Pasta_Ricer

Probationary Member
27
2
Nov 2, 2021
Zanjan, Asia
Oh, then I've been setting the TPS calibration wrong :)

Yep, I expected the same typical pull-up on the cable and shorting by the switch to signal the ECU and I see nothing on it.
I don't think the ECU is non-stock as the GTi version of Galants are really rare here and the only ones actually imported are the '91-92 models. The wiring doesn't differ between those, does it?

Do you have the wiring diagram for the 1G non-turbo ECU? I wanna check the wiring with a multimeter and see if even the cable is good.
Also, you mentioned leaky capacitors. Is that a common thing on these ECUs? I've never taken apart an ECU before, but I have many years of experience in repair of electronics so I can handle it if I can access the PCB.

Thank you so much <3
 

DSMPT

DSM Wiseman
2,175
1,758
Jun 12, 2014
Japan / Mexico, Arizona

steve

DSM Wiseman
14,865
1,721
Feb 3, 2002
Boulder, Colorado
I'd like to know the part number for the GTi ECU if you get the chance.

Between the 90 and 91 model years there were several slight pinout differences in the ECU's. The pin for the IPS being one of those that changed. Not really knowing the 91 Galant GTI-16V I can't say exactly how close it followed the US Galants. I know the GVR4's we got followed the same as the 91+ DSM's.
 

Pasta_Ricer

Probationary Member
27
2
Nov 2, 2021
Zanjan, Asia
Ah, thanks.

Unfortunately, the wiring is fine and it's the ECU.
I took it apart and see that an ECU repairman has written his number on the inside. The caps seem fine and original Nichicons. I don't see any bulging or leaking/corrosion on the leads or the board.
I also don't see any obvious repair done to it and all of the solder joints look kinda old, meaning that it's original.

One thing that doesn't feel right is that this is a 92 model ECU but the car is a 91. I don't know what has changed in this time, but it is a little bit sus.
Also, there is a date written on it next to the number "92/4/6" which I don't know if it's the model of the ECU or the date that the guy has repaired it in Shamsi calendar which would be 9 years ago.
I also noticed that the IPS wire comes to the second one from the right on the bottom of the big connector which I believe is supposed to be on the second left according to the schematic provided by DSMPT?

I have to go on an important trip tomorrow and I need the car functional. I will close it back up and put everything back together and perhaps recheck this when I get back.

I have attached some pictures of the ECU if anyone's interested. I intentionally censored the repairman's number for obvious reasons.

Thank you all once again for the great help. I really appreciate it <3

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DSMPT

DSM Wiseman
2,175
1,758
Jun 12, 2014
Japan / Mexico, Arizona
One thing that doesn't feel right is that this is a 92 model ECU but the car is a 91.
That dual board ECU is from 80s, your ECU is from the early JDM non turbo Galant/Eterna (The early JDM Galant VR4 also had the dual board ECU).
This ECU's idle switch pin is #6. (Please refer the pic below for pin numbers) You would need to connect the idle switch wire to pin #6 in case if yours is connected to pin #14 (This is what Steve mentioned above).
And I am not 100% sure but probably you wouldn't use #14 since it's non turbo ECU.
there is a date written on it next to the number "92/4/6" which I don't know if it's the model of the ECU or the date that the guy has repaired it in Shamsi calendar which would be 9 years ago.
Perhaps it was written in Japan. In Japan it's year/month/day.
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Pasta_Ricer

Probationary Member
27
2
Nov 2, 2021
Zanjan, Asia
Hmm... I see. I confirmed it later that my IPS is in fact connected to pin 14 on the ECU connector.
So I have to connect it to pin 6?
What do I do with the pin already on pin 6?

I doubt the date was written in Japan as the repairman's phone number is written with the same width and color of marker. The same phone number with the same color can be seen under some glue gunk on the main ECU cover.

I ran the car a bit and I have terrible idle which gets really annoying. Turning on the AC causes the RPM to drop to 350-400 and makes the engine make unhappy noises which also makes me unhappy :)
Although winter is near and the warm weather is almost gone, I'd still like to have a functional, automatic idle, even though the small pops and crackles are cool :(

At some point, I will switch the ECU to a MegaSquirt clone that is locally made. That should make things a bit easier, although a bit more expensive. Maybe in a couple of years.

Thanks pal!
 

steve

DSM Wiseman
14,865
1,721
Feb 3, 2002
Boulder, Colorado
Doing a little googlefoo I found

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Unlike the DSM schematic it seems that the IPS wire might be a black on on pin 6.
 

Pasta_Ricer

Probationary Member
27
2
Nov 2, 2021
Zanjan, Asia
Does your car have a tag like this one?

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Yes, sir.

Sorry about the reflections and overall bad photography. It's pretty dark out and my plate has seen better days.

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Doing a little googlefoo I found

Unlike the DSM schematic it seems that the IPS wire might be a black on on pin 6.

Very interesting and certainly helpful. After coming back from my little trip, I'll definitely try putting it on the 6th pin and see what happens. I wonder what's on pin 6 right now
 
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steve

DSM Wiseman
14,865
1,721
Feb 3, 2002
Boulder, Colorado
Thank you. What I was hoping to confirm was that both cars were E33A chassis and that does so. Yours is an manual and the other one was an Automatic.

There seems to be a NA AWD version that I heard called a Galant GSX but I've also seen references to a Galant GTI-16V Dynamic-4 which I'm assuming is the same thing.

I missed your asking about pin numbering earlier. It can be confusing so I wrote awhile back. https://www.dsmtuners.com/threads/how-to-identify-ecu-pin-numbers.246467/
 

DSMPT

DSM Wiseman
2,175
1,758
Jun 12, 2014
Japan / Mexico, Arizona
So I have to connect it to pin 6?
Yes.
What do I do with the pin already on pin 6?
You have to check what's connected to pin #6 now. Can't say for sure but #6 could be blank now? (If it was a turbo car, just switch #6 and #14). If so, just de-pin #14 like the video in the link below and switch to #6 and leave #14 as blank.
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I doubt the date was written in Japan as the repairman's phone number is written with the same width and color of marker. The same phone number with the same color can be seen under some glue gunk on the main ECU cover.
It was just an idea. Was not that important :)
 

DSMPT

DSM Wiseman
2,175
1,758
Jun 12, 2014
Japan / Mexico, Arizona
Forgot to mention one thing, JDM don't have EGR but it has a post CAT high temp sensor instead, which is connected to ECU pin #11 and #15. I am not so sure if you can leave it or you need to do something for that but in case if your car is the Cali model, maybe you should disconnect the EGR temp sensor at least (or some sort of bypass may be required). I had the mid/late JDM Galant VR4 ECU in my 1g US DSM. The mid Galant ECU pinout is supposed to be the same as the early Galant one and IIRC I could use it without doing anything but my car is not Cali and has the EGR deleted. Excuse me if I am wrong.
 

steve

DSM Wiseman
14,865
1,721
Feb 3, 2002
Boulder, Colorado
Hiroshi, most of the schematic I posted I can identify the symbols without reading Japanese but can you help with a few on the bottom of


I'm interested to know what connected to pin 5, (15, 11), and 12?

Unless I missed it I don't think this ECU uses pin 14 at all so there is no MAF reset just like the rest of the NA cars even if he has a wire on 6 right now. But I'd like to see a picture of the harness plugged in to be sure.
 

DSMPT

DSM Wiseman
2,175
1,758
Jun 12, 2014
Japan / Mexico, Arizona
I'm interested to know what connected to pin 5, (15, 11), and 12?
@steve, #15 and #11 (GND) is the one I mentioned above, the CAT high temp sensor. That's the one that causes the CAT warning light turned on in dash in JDM cars when it detects 900°C. Japanese 1G/2G Eclipse also have it. #5 is power steering pressure switch. #12 is the ignition timing/SAS adjustment connector. Believe the same as DSM?
Unless I missed it I don't think this ECU uses pin 14 at all so there is no MAF reset just like the rest of the NA cars even if he has a wire on 6 right now. But I'd like to see a picture of the harness plugged in to be sure.
That's what I thought, too.

Found some pics in google. This is for Pajero but I think basically the same.
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Pasta_Ricer

Probationary Member
27
2
Nov 2, 2021
Zanjan, Asia
Forgot to mention one thing, JDM don't have EGR but it has a post CAT high temp sensor instead, which is connected to ECU pin #11 and #15.
Hello again.

Back from my trip and I will do the pin swap tomorrow morning.

My car being an UAE import, I doubt it has an EGR temperature sensor. I can confirm this by the amount of gunk that had blocked the tiny hole in the EGR and the ECU never complained about it :)

I actually cleaned the EGR a lot, but the vacuum doesn't pull it open so my cleaning basically had no actual benefit apart from a kilo of removed gunk from all these years of service.

And for the record, my car is not turbo'ed. Factory GTi-16V N/A FWD.

@steve, #15 and #11 (GND) is the one I mentioned above, the CAT high temp sensor. That's the one that causes the CAT warning light turned on in dash in JDM cars when it detects 900°C. Japanese 1G/2G Eclipse also have it. #5 is power steering pressure switch. #12 is the ignition timing/SAS adjustment connector. Believe the same as DSM?

That's what I thought, too.

Found some pics in google. This is for Pajero but I think basically the same.

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I don't know about any cat temp sensor. My car doesn't turn on the check engine light even when doing a constant WOT pull from 1st gear to the middle of 3rd. I haven't seen any sensor around the exhaust, but I could be wrong.

Does mine even have a narrow-band O2 sensor? Or is that turbo only?

Anyway, really excited about tomorrow. Just getting a proper idle would be a huuuuuge help, especially with the decent new sound system installed. When it bogs down a tiny bit after pushing the clutch in quickly, the steering wheels gets hard cause of the really low RPMs which makes turning in tight spots incredibly difficult with my new 195R17 tires.

Thanks for all your help, DSM people :D
 
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DSMPT

DSM Wiseman
2,175
1,758
Jun 12, 2014
Japan / Mexico, Arizona
And for the record, my car is not turbo'ed. Factory GTi-16V N/A FWD.
Yes, we are aware of that.
I don't know about any cat temp sensor.
I don't know about UAE cars, but if you have one like Japanese cars, you would find a temp sensor on the CAT, like the pics below. (The pic are taken from google)
Does mine even have a narrow-band O2 sensor?
Yes, it does.
Anyway, really excited about tomorrow. Just getting a proper idle would be a huuuuuge help
We hope it gets better. Please report back to us.

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Pasta_Ricer

Probationary Member
27
2
Nov 2, 2021
Zanjan, Asia
I just took out the connector and LOL, my pin 6 is empty. Imma do the 14 to 6 swap and take out the car for a spin after I confirm that I get 5V on the IPS when on throttle.

Fantastic! I see 12V when the throttle is open and 0V when closed :D

I do have a slight problem that closing the throttle slowly doesn't really activate the IPS. I have driven it in a bit to stop the TB blade from binding, but might have to do it a little bit more.

I will reset the ECU so it can re-learn the ISC/IAC values and get a proper idle.

Will test and give you all the details shortly.

Thank you all so much for all the help <3

Hmm... The car feels much better now when you let off the throttle, but the idling doesn't sound very nice.

Turning on the AC also makes it dip quite a bit, making the engine shake like crazy.

My ISC/IAC makes the typical tik-tik-tik sound when you put the switch in the ON position, but doesn't control the idle properly? I don't know if I can take apart the ISC/IAC without taking out the TB which is huge pain, especially because I don't have a proper TB to intake manifold gasket and I apply gasket maker to seal it.

I also don't have a vacuum leak as the BISS is very touchy throughout its movement, something that wasn't possible back when I had a vacuum leak.

I have cleaned the ISC/IAC with a spray twice before which had made the tip a bit loose when turning it side to side (only slightly, like 1mm or something). It used to be full of gunk. I also rubbed a bit of clean motor oil on the gasket to prevent vacuum leaks.

I really don't wanna get a new ISC/IAC as they are pretty darn expensive here.

Also, the family says the exhaust smells a lot less now, but I don't know if it's because the engine is running less rich now or the "cleaned" EGR has just started doing its job (it used to be so stiff that the vacuum couldn't open it, even after cleaning it and unclogging the bypass hole).
 
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DSMPT

DSM Wiseman
2,175
1,758
Jun 12, 2014
Japan / Mexico, Arizona
My pin 6 is empty
Yeah that' what we thought.
Fabtastic! I see 12V when the throttle is open and 0V when closed :D
I do have a slight problem that closing the throttle slowly doesn't really activate the IPS. I have driven it in a bit to stop the TB blade from binding, but might have to do it a little bit more.
This sounds like the idle position switch is a bit off. You should adjust it first if it's off. The TPS should also be adjusted at the same moment. Then check the ISC if you think it's not working properly. Please refer the pics below.


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Pasta_Ricer

Probationary Member
27
2
Nov 2, 2021
Zanjan, Asia
Yeah that' what we thought.

This sounds like the idle position switch is a bit off. You should adjust it first if it's off. The TPS should also be adjusted at the same moment. Then check the ISC if you think it's not working properly. Please refer the pics below.


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Well, my IPS is adjusted correctly and I just freshly adjusted the TPS like your instructions at the ECU connector to 4.85V when off and 4.90V when on.

Now, when you put it in the ON position, until the CEL turns off, the stepper motor continously ticks and stops when the CEL turns off. I turned the engine on and let it warm up. I took a listen and heard the stepper motor ticking once every few seconds, probably trying to correct the idle.

I turned it off, disconnected it, and tested the coils of the stepper motor per the instructions. Unfortunately, I have no resistance between pin 5 and 6 of the stepper motor. It's gone completely open. The rest have a resistance of 36R which I assume is correct as the engine bay had gotten hot.

I wonder if I can take apart the stepper motor and check for broken wires for the coil. I don't remember if it had any screws for opening it up.
Has anyone ever tried to repair one of these?
 

Pasta_Ricer

Probationary Member
27
2
Nov 2, 2021
Zanjan, Asia
BTW, anyone know what these modules are on the left of the ECU, behind the glove box? The yellow-ish one is mounted on the underside of the metal rail.

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DSMPT

DSM Wiseman
2,175
1,758
Jun 12, 2014
Japan / Mexico, Arizona
Well, my IPS is adjusted correctly and I just freshly adjusted the TPS like your instructions at the ECU connector to 4.85V when off and 4.90V when on.

Now, when you put it in the ON position, until the CEL turns off, the stepper motor continously ticks and stops when the CEL turns off. I turned the engine on and let it warm up. I took a listen and heard the stepper motor ticking once every few seconds, probably trying to correct the idle.

I turned it off, disconnected it, and tested the coils of the stepper motor per the instructions. Unfortunately, I have no resistance between pin 5 and 6 of the stepper motor. It's gone completely open. The rest have a resistance of 36R which I assume is correct as the engine bay had gotten hot.

I wonder if I can take apart the stepper motor and check for broken wires for the coil. I don't remember if it had any screws for opening it up.
Has anyone ever tried to repair one of these?
Your ISC is dead. You can still easily find a good used OEM one for cheap.

BTW, anyone know what these modules are on the left of the ECU, behind the glove box? The yellow-ish one is mounted on the underside of the metal rail.

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The 1st pic is blower motor resistor. The 2nd pic is MPI relay.
 

Pasta_Ricer

Probationary Member
27
2
Nov 2, 2021
Zanjan, Asia
Your ISC is dead. You can still easily find a good used OEM one for cheap.
They're not that cheap in here :(
But yeah, I have to get a new one. I opened this one up and the coils are potted in resin. It appears that it had gotten stuck and the transistors in the ECU pushed a lot of current through it, overheating the coils and killing it.
It was incredibly dirty around the IAC hole where it sat and the shaft was stuck when I first took it out along with the TB to clean.

The 1st pic is blower motor resistor. The 2nd pic is MPI relay.
Ah, I see. Thanks!
 
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