Idle Speed Motor ***SPLIT from Liner Seals***

[Giamanut]

Just Finished my head gaskets and they work fine! I did have anti go by my liner seals at some point however I don't think they provide much of a seal with nothing holding them down. Anyway before I go to far along I just torqued the heads to 45 LB ft. and with the oil plug out filled the engine with coolant If it was gonna leak it would have came out the oil plug. No coolant getting by the seals so I finished the install and went for a drive! Pretty cool but the 21 year old tires have got to go! LOL
Did have some idle issues but got that on the run. Trouble shot that to IAC motor not closing all the way. Close loop Idle goes to 1500 and FV goes to 136 % to compensate for the air going through the IAC tapping on the IAC reduced Idle but plugging the pipe of agony and setting the butterflies to 750 cured it so I have a new IAC motor on the way.
So far here is what I have working on the car
Mirrors
Clock
Antenna
windows
washer/ wipers
Clutch
Brakes
fuel gauge
speedometer
all lights
cigarette Lighter
Heater
AC
Roof box repair
Lambda System
Radiator
cooling fans
horns
various relays
and Circuit breakers
and of course
Head gaskets and water pump.
that took about 5 weeks with my work schedule
I work 4 tens so about 15 days.
Still need to do a proper AC charge,
change the IAC
1 blinker indicator
Odometer trip reset
Tires
At that point as far as I can tell 5051 should be very close to 100%
Glad to see your doing well with your project also!

[Bitsyncmaster]

Did have some idle issues but got that on the run. Trouble shot that to IAC motor not closing all the way.

FYI:

With the stock idle ECU the idle motor does not close all the way. The amount it can close is dependent on the thermistor resistance. Higher resistance (cold engine) the IAC can not close much under 1/3 open and even with the hot engine it still will not close all the way. That is how the ECU provides a "fast idle" when you first start a cold engine. And the amount of fast idle is very dependent on how you have the adjustments done on the engine. That is also why you get 2000 to 3000 idle RPM if your thermistor gets an open circuit.

[Giamanut]

FYI:

With the stock idle ECU the idle motor does not close all the way. The amount it can close is dependent on the thermistor resistance. Higher resistance (cold engine) the IAC can not close much under 1/3 open and even with the hot engine it still will not close all the way. That is how the ECU provides a "fast idle" when you first start a cold engine. And the amount of fast idle is very dependent on how you have the adjustments done on the engine. That is also why you get 2000 to 3000 idle RPM if your thermistor gets an open circuit.

Thanks. Right the IAC does not seal shut. But mine is sticking too far open in closed loop, I would think the difference in how far it closes at 1500 and 750 Rpm is not a lot. When I tap on it it does close a little further and drops the rpm to about a 1100.
Idle does not hunt or surge. FV duty cycle percentage is way high in closed Loop which tells me the Lambda system is working, just need less air to bring that down. I will post the fix. But so far Fuel Pressure is good Timing is right No external vac leaks.
It does rev good so mixture is close but not right yet WOT switch works. coming up on days off again so should get another look at it soon.

[Giamanut]

+1

Another problem is when your deceleration valves are bad. That extra vacuum leak makes the Idle motor run to it's minimum opening. The idle motor has very little torque at the extreme ends and any sticking will most likely happen then. When I designed my idle ECU I noted the best torque at the center value (FV duty cycle at 50%). What I did to get a little better was to reduce the frequency of the motor control from 100 Hz. to 66 Hz.

So going back to the thermister for a second. What i got from the manual is that under 59 degrees it closes and provides power or ground to a separate circuit in the Idle ECU and just opens above 59 So if it were unplugged it could not activate the High Idle circuit in the ECU. Am I reading that wrong? I know you are the guru on this ECU. Also when I come off the idle switch the IAC stops as it should so that is working If the thermister was stuck closed it would keep the IAC open more than it should be when warm but unplugged it should just kill the High Idle circuit. Correct? I don't know if that is right?

[Bitsyncmaster]

So going back to the thermister for a second. What i got from the manual is that under 59 degrees it closes and provides power or ground to a separate circuit in the Idle ECU and just opens above 59 So if it were unplugged it could not activate the High Idle circuit in the ECU. Am I reading that wrong? I know you are the guru on this ECU. Also when I come off the idle switch the IAC stops as it should so that is working If the thermister was stuck closed it would keep the IAC open more than it should be when warm but unplugged it should just kill the High Idle circuit. Correct? I don't know if that is right?

The thermistor feeding the idle ECU is a variable resistance. From memory it normal runs from about 50 Kohm cold to less than one Kohm hot. From about 50 Kohm (or higher) to 10 Kohms it varies how far the idle motor will close. The idle switch does nothing I can find with the operation of the stock idle ECU. The idle switch turns the ignition advance on if the switch is open on a warm engine. If the switch is closed it turns the advance off on a warm engine. If the engine is cold you do not get advance either way.

With a stock idle ECU the idle motor never shuts off and it does close the idle motor if your above 775 RPM. With the idle motor closed you probably would not feel vibration because of the very small duty cycle but it is still powered.

With my ECU I also close the idle motor (above 1500 RPM) but I power the idle motor down for most of the time. I do power it up for a very short time about every 10 seconds to make sure the idle motor valve stays closed. I do that to save electrical power, less heating of the idle motor and reduce wear on the idle motor bearings.

[Giamanut]

The thermistor feeding the idle ECU is a variable resistance. From memory it normal runs from about 50 Kohm cold to less than one Kohm hot. From about 50 Kohm (or higher) to 10 Kohms it varies how far the idle motor will close. The idle switch does nothing I can find with the operation of the stock idle ECU. The idle switch turns the ignition advance on if the switch is open on a warm engine. If the switch is closed it turns the advance off on a warm engine. If the engine is cold you do not get advance either way.

With a stock idle ECU the idle motor never shuts off and it does close the idle motor if your above 775 RPM. With the idle motor closed you probably would not feel vibration because of the very small duty cycle but it is still powered.

With my ECU I also close the idle motor (above 1500 RPM) but I power the idle motor down for most of the time. I do power it up for a very short time about every 10 seconds to make sure the idle motor valve stays closed. I do that to save electrical power, less heating of the idle motor and reduce wear on the idle motor bearings.

D:05:02 workshop manual. The idle speed control system is only in operation when a microswitch (Fig. 37) (1) is closed by the throttle plates being in a fully closed position. This switch is located on the engine throttle linkage and allows the ECU module to operate. The ECU module senses engine speed from the tachometer and activates the idle speed regulator. The regulator changes the position of the rotary air valve in order to maintain a specified idle speed.
So what am I missing? Does the IAC still get power off idle but the ECU don't?
Also "A thermistor (3), located in the coolant system distribution pipe, will activate another circuit within the ECU module when the coolant temperature is below 15°C (59°)F. This circuit will provide a fast idle condition."
This statement makes it appear that the thermistter only effects the fast idle circuit in the ECU.
I don't get it, I know you know what your talking about but this is out of the manual. It does look as though the Themister is variable as you state. So off idle the motor is powered but the ECU is not????????????????

[Bitsyncmaster]

D:05:02 workshop manual. The idle speed control system is only in operation when a microswitch (Fig. 37) (1) is closed by the throttle plates being in a fully closed position. This switch is located on the engine throttle linkage and allows the ECU module to operate. The ECU module senses engine speed from the tachometer and activates the idle speed regulator. The regulator changes the position of the rotary air valve in order to maintain a specified idle speed.
So what am I missing? Does the IAC still get power off idle but the ECU don't?
Also "A thermistor (3), located in the coolant system distribution pipe, will activate another circuit within the ECU module when the coolant temperature is below 15°C (59°)F. This circuit will provide a fast idle condition."
This statement makes it appear that the thermistter only effects the fast idle circuit in the ECU.
I don't get it, I know you know what your talking about but this is out of the manual. It does look as though the Themister is variable as you state. So off idle the motor is powered but the ECU is not????????????????

The engineers may have wanted it to work like that but it does not. The ECU runs all the time power is on (Key on). The idle motor gets power (12 volts to the center pin) from the ECU when the ECU gets power. The ECU then drives one side of the motor to ground until the duty cycle changes then the other side of the motor is driven to ground. The idle switch does not turn the the duty cycle drivers off. They drive all the time there is power to the ECU.

You can test it by looking at the voltage or the duty cycle at the idle motor. Press the idle switch and release it and see what you get. If you have the idle motor in your hand you will feel it vibrate all the time.

[Giamanut]

Right, keeping this coolant where it belongs is the name of the game.

Yep that is for sure. I do suspect those seals are pretty stout and maybe a little more forgiving than they appear to be. I mean seems like they would be hard to mess up, indeed trying to match paper or metal expansion to steel and aluminum has got to leave a wide margin for error. So when people say use the fattest shims I agree, they will flatten right in to position. Now if you over heat your engine all bets are off!

[Giamanut]

The engineers may have wanted it to work like that but it does not. The ECU runs all the time power is on (Key on). The idle motor gets power (12 volts to the center pin) from the ECU when the ECU gets power. The ECU then drives one side of the motor to ground until the duty cycle changes then the other side of the motor is driven to ground. The idle switch does not turn the the duty cycle drivers off. They drive all the time there is power to the ECU.

You can test it by looking at the voltage or the duty cycle at the idle motor. Press the idle switch and release it and see what you get. If you have the idle motor in your hand you will feel it vibrate all the time.

I am heading over to the car right now with a new small IAC motor will check it all out and post tonight when I get back. Thanks. like I said I don't don't you just getting my head around this is a bit of a task!
Will post back soon!

[Bitsyncmaster]

I am heading over to the car right now with a new small IAC motor will check it all out and post tonight when I get back. Thanks. like I said I don't don't you just getting my head around this is a bit of a task!
Will post back soon!

Yes with the motor in your hand, you will know it never shuts off.

FYI:

The smaller Volvo motor is much better than the OEM because it runs without dead spots and draws half the current. I run it without any bracket holding it and it stays in place just fine.