Car just dies!
Registered User
Joined: Jan 2005
Posts: 1,396
From: Phoenix, Arizona
Originally Posted by Z Car Barbie
Also, I don't want to argue about this here, because it only confuses people, sends mixed signals, and extends the search time for anyone seeking this info. I think it'd be best if we IM or PM each other to settle our differences, and if you prove me wrong, I'll be the first to admit it, and post it for everyone else to see. 
Registered User
Joined: Jan 2005
Posts: 1,396
From: Phoenix, Arizona
Originally Posted by my86z
Wich z31 TPS' are potentiometers?
Both of my 86's have switches.
Both of my 86's have switches.
From my previous post:
Originally Posted by AZ-ZBum
Now, there are TPS's with potentiometers. But all of those are for automatic transmission control. They do not affect the ECU to motor connection in any way, shape, or form.
Last edited by AZ-ZBum; Nov 1, 2006 at 03:44 PM.
Registered User
Joined: Jan 2005
Posts: 1,396
From: Phoenix, Arizona
This should help eliminate the confusion....
The information I'm posting can be verified in the factory service manual.
Start TPS/TVS lesson:
The Throttle Valve SWITCH has two settings. On or off. It will allow electricity to flow or it won't.
The throttle body has an infinate number of positions between 0 and 90 degrees. Think of 0 as a closed throttle and 90 as a wide open throttle.
If the TVS is adjusted properly, when the throttle is closed (0 degrees), the TVS has a closed contact and electricity flows. Thus, since the ECU is sending signal, it will get back a signal.
As soon as the throttle is opened any amount (1 degree), the TVS no longer is closed and is now opened. An open circuit sends NO electricity. Thus, the ECU sees 0 volts.
So, for any position from 1 degree (barely pushing the gas) to 90 degrees (full throttle), the ECU sees 0 volts. And since at any and all of those positions, it sees 0 volts, it doesn't know if the car is at quarter, half, or full throttle.
If you wish to verify, see the following pages:
84 FSM: EF&EC 50
85 FSM: EF&EC 47
86 FSM: EF&EC 63-64
87 FSM: EF&EC 70-71
88 FSM: EF&EC 96-97
89 FSM: EF&EC 96-97
End of TVS lesson.
Start of AC/idle up lesson:
At no point in the Z31 does the ECU talk to any part of the AC system. The only reason the AC talks to the ECU is to tell it that it's on so the ECU can activate the idle up control device.
So, if this is true, then at no point in time can the ECU turn the AC off or even slow it down.
Incidently, the same signal that feeds this contact on the ECU is also fed by the following conditions:
- power steering pump
- lights
If you are getting a code 31, turn on your lights and see if it goes away. It should.
If you wish to verify, see the following pages:
84 FSM: EF&EC 51
85 FSM: EF&EC 48
86 FSM: EF&EC 67-68
87 FSM: EF&EC 97
88 FSM: EF&EC 141
89 FSM: EF&EC 141
End of Idle up signal lesson.
If, for any reason, your AC deactivates or slows down while accelerating, it is because you have a vacuum leak. Since every Z31 is getting to be, or already is around 20 years old, it stands to reason that most AC systems are not up to the task of maintaining a proper vacuum.
And because it was asked for, here are two dyno charts from two totally different cars with properly functioning AC systems. At no time did the cold air coming out of the vents slow down or get warm.
1984 Nissan 300ZX non turbo:
1998 Lexus GS300
I would have a sheet for my Scion xB, but I gave it away when I sold the car. The chart looked exactly the same. A consistent ~8hp drop across the RPM range.
Now, if you want to continue arguing these points, I suggest you get your FSM out, sit in your car, and try to discuss these things with them. Because it doesn't matter what you THINK. All that matters is what is really there. And yes. I do have to be right. Especially when I am right.
The information I'm posting can be verified in the factory service manual.
Start TPS/TVS lesson:
The Throttle Valve SWITCH has two settings. On or off. It will allow electricity to flow or it won't.
The throttle body has an infinate number of positions between 0 and 90 degrees. Think of 0 as a closed throttle and 90 as a wide open throttle.
If the TVS is adjusted properly, when the throttle is closed (0 degrees), the TVS has a closed contact and electricity flows. Thus, since the ECU is sending signal, it will get back a signal.
As soon as the throttle is opened any amount (1 degree), the TVS no longer is closed and is now opened. An open circuit sends NO electricity. Thus, the ECU sees 0 volts.
So, for any position from 1 degree (barely pushing the gas) to 90 degrees (full throttle), the ECU sees 0 volts. And since at any and all of those positions, it sees 0 volts, it doesn't know if the car is at quarter, half, or full throttle.
If you wish to verify, see the following pages:
84 FSM: EF&EC 50
85 FSM: EF&EC 47
86 FSM: EF&EC 63-64
87 FSM: EF&EC 70-71
88 FSM: EF&EC 96-97
89 FSM: EF&EC 96-97
End of TVS lesson.
Start of AC/idle up lesson:
At no point in the Z31 does the ECU talk to any part of the AC system. The only reason the AC talks to the ECU is to tell it that it's on so the ECU can activate the idle up control device.
So, if this is true, then at no point in time can the ECU turn the AC off or even slow it down.
Incidently, the same signal that feeds this contact on the ECU is also fed by the following conditions:
- power steering pump
- lights
If you are getting a code 31, turn on your lights and see if it goes away. It should.
If you wish to verify, see the following pages:
84 FSM: EF&EC 51
85 FSM: EF&EC 48
86 FSM: EF&EC 67-68
87 FSM: EF&EC 97
88 FSM: EF&EC 141
89 FSM: EF&EC 141
End of Idle up signal lesson.
If, for any reason, your AC deactivates or slows down while accelerating, it is because you have a vacuum leak. Since every Z31 is getting to be, or already is around 20 years old, it stands to reason that most AC systems are not up to the task of maintaining a proper vacuum.
And because it was asked for, here are two dyno charts from two totally different cars with properly functioning AC systems. At no time did the cold air coming out of the vents slow down or get warm.
1984 Nissan 300ZX non turbo:
1998 Lexus GS300
I would have a sheet for my Scion xB, but I gave it away when I sold the car. The chart looked exactly the same. A consistent ~8hp drop across the RPM range.
Now, if you want to continue arguing these points, I suggest you get your FSM out, sit in your car, and try to discuss these things with them. Because it doesn't matter what you THINK. All that matters is what is really there. And yes. I do have to be right. Especially when I am right.
User Friendly
Joined: Oct 2003
Posts: 1,045
From: Formerly Atlanta, GA; now Central FL
Originally Posted by AZ-ZBum
The information I'm posting can be verified in the factory service manual ... At no point in the Z31 does the ECU talk to any part of the AC system. The only reason the AC talks to the ECU is to tell it that it's on so the ECU can activate the idle up control device.
If you wish to verify, see the following pages: 84 FSM: EF&EC 51, ...86 FSM: EF&EC 67-68
If you wish to verify, see the following pages: 84 FSM: EF&EC 51, ...86 FSM: EF&EC 67-68
I have the 84 and 86 FSM's, and the pages you referenced don't verify what you're saying - that's just your interpretation. I have my own interpretation, so it doesn't really matter - no point in debating it anymore, because we're obviously not going to agree. 
Queen of Yachts
Joined: May 2006
Posts: 2,957
From: warmspott, trollville.......somewhere sailing the seas--fla, virgin islands...wherever....warm water....LOL
my 86 NA exhibited no signs or symptoms of problems--one day on the way to LA, she decided to just quit while going about 85 mph. dark and quiet--no dash, no headlites, nada, nothing. after cussing her put royally and missing work, i found the problem--my AC compressor had a wire that decided just then to cause a fire. it would not hurt to check your AC--but the only reason to do so is just in case yours has the same disease mine had---whatever made it decide to burn.----wiring. overloaded circuit asnd stopped entire progress. does not make sense to me, but cost a lotta dollas. retail.
Thread
Thread Starter
Forum
Replies
Last Post
Bookmarks
