Fc3s stuffs for exchange/sell
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Ok nice dudes.
Eh email ne at [email protected] lets confirm on Friday
Meanwhile i have another 2 to come by
Eh email ne at [email protected] lets confirm on Friday
Meanwhile i have another 2 to come by
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You guys should come and tt up in Subang. We have a couple of nice and friendly FC owners here. Later can wangan a bit to Klang. If you guys interested let me know and we can plan something. Later then.:regular_smile:
Bro ATKT ,
Well it all depends on the group lah .KL is very best lah for shoipping .
Let me ask the guys but if Melaka also nice quite close for us for such as short trip .
Let me discuss with them .
Sayung about parts,anyone has s4 original BAC valve for idle control?As now im using mehcanical valve.
Thanks
Well it all depends on the group lah .KL is very best lah for shoipping .
Let me ask the guys but if Melaka also nice quite close for us for such as short trip .
Let me discuss with them .
Sayung about parts,anyone has s4 original BAC valve for idle control?As now im using mehcanical valve.
Thanks
Ok ,
Can you explain to me what the BAC does actually ?Currently what i have now is some sort of mechanical / spring adjuster thing at the intak emanifold .
As im changing to a new ecu ,i want the ecu to be able to control the idling instead of what i m dong now ,mechanically with my Microtech .
Please advise
Can you explain to me what the BAC does actually ?Currently what i have now is some sort of mechanical / spring adjuster thing at the intak emanifold .
As im changing to a new ecu ,i want the ecu to be able to control the idling instead of what i m dong now ,mechanically with my Microtech .
Please advise
- Joined
- Oct 18, 2006
- Messages
- 215
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- 1,516
To Maxezin, I do hope this helps.
Diagnosing and Correcting TurboII Idle Problems
Over the time I have been involved with the Rx7 and TeamFC3S mailing lists, I have frequently heard complaints surrounding idle problems. Recently, I had my own run-in with idle problems and, with the help of Barrington Daltrey, a similarly afflicted member, learned a great deal about the idle circuit. Given the number of people who seem to encounter this problem, I would like to share what we learned with the rest of the Rx7 community. Given that most of our problems centered around the BAC valve, this writeup will likely be strongest in that area. There is still a lot we don't know, particularly as it relates to other Rx7 models and later years of the TII. Hopefully, those of you who have those cars can help us fill in the missing information.
Idle Circuit Theory of Operation
Hmmm... Where are my idle and fast idle set screws? The idle system on the 2nd generation RX7 consists of three electronically controlled solenoid valves. The Emissions Control Unit (ECU), which is really the engine management computer, controls the opening of these valves based on signals from the
On Turbo II's, the BAC valve is located on the side of the intake manifold, above the turbo and Air Control Valve. It is a horizontal cylinder with a black plastic cap on the forward end. There are four hoses that connect to the valve. The two hoses that enter and exit parallel to the center axis of the valve are water hoses. The hose on the bottom is the air intake hose. The hose on the top is the air supply hose for the Air Bypass Solenoid valve.
The BAC valve is (unlike the other two valves) a variable valve whose opening is controlled by a duty cycle signal from the computer. This signal is a square wave with a variable duty cycle. The duty cycle of a square wave is the percentage of the time that the signal is in the "on" state vs. the total time to complete a cycle. The higher the duty cycle, the more power is transmitted to the device. This is depicted in Figure 1. The computer can increase the opening of the BAC valve, and thereby the engine speed, by increasing the duty cycle of the signal it sends to the BAC valve.
http://www.teamfc3s.org/info/pics/articles/figure1.jpg
All three of these valves are controlled by "open collector" transistor outputs. In this configuration, the transistor is a simple switch connected between the device and ground. The circuit and the equivalent circuit are depicted in Figure 2. When the transistor gets a positive signal voltage from the computer, it conducts and the circuit is completed through the solenoid to ground. This creates an opening force on the valve.
In the case of the BAC valve, the switch is opening and closing 125 times per second (125 Hz). This means that a complete cycle takes 8 mS. With the AC off, the transistor is "on" for about 2.4 mS which gives a duty cycle of 30%. When the AC is turned on, it requires a significant amount of aditional power from the engine. As many 2nd gen owners have experienced, if something isn't done to increase the air available at idle, the engine will die. The ECU senses that the AC is on by monitoring the signal from the AC compressor clutch. When it is engaged, the "on" time of the signal to the BAC valve is increased to 5.2 mS, which brings the duty cycle up to 65%. More power is transmitted to the BAC valve and the idle speed increases to compensate for the power loss to the compressor.
The idle adjust screw appears to control the quantity of air that flows through a bypass passage around the BAC valve.
Air Supply Valve
The Air Supply Valve is located near the firewall on the rear side of the intake manifold. It is a simple on/off valve that, when on, supplies a metered quantity of air to the engine to compensate for the power requirements of the power steering pump. The ECU turns it on when it sees a signal from the power steering switch on the power steering pump. Again, it is an "open collector" circuit.
If you notice a significant dip in your idle speed when you turn the steering wheel, something is wrong in the Air Supply Valve circuit. Given the location of the thing, it is going to be a bear to replace.
Notice the warning in the manual "Do not tamper with the adjust screw." Hah!
Air Bypass Solenoid Valve
The Air Bypass Solenoid Valve is the valve on top of the intake manifold on the passenger side of the intercooler. Above and slightly behind the BAC valve. It is a simple on/off valve that, when on, supplies the additional air required to create that high idle on cold start. It is in series with the BAC valve, so if the BAC valve is not opening correctly, the fast idle will not occur.
Summary
One has to wonder: "Why the complexity?". The function of all three valves could have been covered by the BAC valve alone, probably by simply changing software. This would have significantly reduced the complexity of the ECU electronics as well as the number of hoses running around.
Barrington Daltrey and I have discussed the possibility of creating an add-on circuit which takes the approach of monitoring the engine speed directly and changing the opening of the BAC valve accordingly. This would have the affect of compensating for any change in load (whether it be AC, power steering, or that killer stereo and alternator you want to install). I believe in this idea enough that I have started designing such a circuit. More on that in the future.
Anyway, all these components provide plenty of things to go wrong with the your car's idle quality.
Diagnosing Turbo II Idle Problems
There are a variety of possible failure modes in the idle circuit. This writeup describes trouble-shooting to identify the most common causes of problems. The first five items thoroughtly check the idle control loop, centered on the BAC control circuit. The shop manual adequately describes how to check the other components and sensors. The next few items give a couple of other things that can be checked and, finally, help is offered in case the ECU is found to be defective.
Symptoms:
1. Check to see if a jumper has been left in the initial set connector. It's easy to forget to remove this after adjusting idle speed. On '87-'88 models, the initial set connector is a green connector with two female spade connectors in it, placed at right angles to each other. It is located in the engine compartment, forward on the driver's side, near the headlight. On later models, it is a single conductor connector, located in about the same position. In these models, a jumper is connected between the connector and ground.
2. Check the Throttle Position Sensor setting. A variety of instructions for doing this are contained in the FAQ. My personal favorite is the two light bulbs. After setting it, rev the engine a couple of times to let everything settle back into place, and re-check it. You may even want to take the car for a quick drive and re-check the setting. An incorrectly set TPS seems to be the most frequent idle culprit. Make sure you get it right.
If you are still having problems, you probably have some kind of component failure. The tests now get a little more sophisticated.
3. Turn off the ignition. Remove the connector from the BAC valve and check the resistance of the BAC valve solenoid. This is done by connecting an ohm-meter across the BAC valve terminals. Care must be taken not to let the probes touch each other or you will get a false reading. You should get somewhere between 10 and 20 ohms. The manual says 10.7 to 12.3 ohms, but it's really not that picky. What you don't want is near zero ohms (solenoid is shorted) or very high resistance (solenoid is open-circuit.) If you have a shorted or open-circuit solenoid, you will need to replace the BAC valve. You might want to try disassembling it just on the off chance that it is repairable.
4. With the connector still removed, and the engine still off, place a 10k ohm, 1/4 watt resistor across the terminals of the connector. This is easy to do, simply insert the resistor leads into the connector. Make sure that the leads of the resistor do not short against each other or anything else. Turn the ignition on, without starting the car, and measure the AC voltage across the resistor. You should get a value between 6 and 7 volts after it settles down. A voltage lower than 5V indicates a likely ECU failure. Go here for more information. If you get the correct voltage, move on to the next step.
NOTE: This is a good chance to check that the conductors in the connector are firmly seated. Mine came loose, slid down, and shorted out, causing ECU failure. More on that in a moment. At the very least, if they are sliding around, they aren't making good contact. If you find that the conductors are loose in the connector, press the wires from the back of the connector towards the front. They should snap into place and not slide back. If they do slide back, you will need to either get a new connector, or epoxy them in, like I did. It works. (Be careful not to get epoxy on the connector surfaces!)
NOTE: Do not perform the following test if you obtained a reading of 0 ohms (short circuit) when you measured the resistance of the solenoid above. Something will get *very* hot.
5. The BAC valve may be stuck. Using jumper wires, connect 12V across the solenoid leads, being extremely careful not to create a short. If you didn't get an open-circuit reading when you measured the resistance of the BAC valve, the valve should click. If it is stuck, doing this a couple of times should free up the valve. I would also recommend removing the BAC valve from the intake manifold (this can be accomplished without removing the water hoses connected to the valve) and spraying WD-40 into it. Work it a few more times with 12V. If you can't get the thing to click this way, replace the BAC valve.
If you got to this point and you are still having idle problems, the problem is not in the electronic idle control system. Here are a few other possibilities and a few ways to check them:
1. Vacuum Leak
Vacuum leaks are frequently the cause of rough idle. A leak ruins your idle by allowing un-metered air to enter the intake manifold, creating a lean air-fuel mixture. Leaks typically develop as a result of vacuum or pressure hoses coming loose or failing, or gasket failures.
Vacuum leaks are frequently diagnosed and located by spraying some kind of flammable substance around the engine. When the flammable substance is sucked in through the leak, the lean condition is temporarily rectified and the engine will speed up. As can be imagined, spraying flammable substances around hot, running engines is a potentially very dangerous practice. It may best be left to qualified service personnel. "Poof, no eybrows!!" I don't even want to suggest flammable substances that can be used here.
A safer method that I have sometimes used successfully is to use a mechanic's stethoscope or a piece of vacuum tubing stuck in your ear. Use the other end to probe around the engine, listening for a hissing or whistling noise. I have successfully found both vacuum and exhaust leaks using this method.
2. Leaks in Intake Hoses
Leaks in the intake hoses after the Mass Airflow Sensor can result in bad idle in exactly the same manner as the vacuum leak. Again, the problem is unmetered air entering the engine. The best way to find these is simply by inspecting all of the components between the MAF and the throttle body.
On a TII, the problem is frequently the hose that connects the MAF to the turbo inlet. This hose has a tendancy to split, which lets air pass. A very small split can cause pretty big problems. Splits can sometimes be fixed with some RTV, but you need to be careful not to let the stuff get into the turbo. Also, make sure you use sealant that is O2 sensor safe. If you can afford it, or have access to a good used, hose, replace it.
3. Obstructed Exhaust System At least one Rx7 list contributor has had problems with his idle as a result of plugged catalytic converters.
This little article curtosy of Team FC3S. Thanks.:regular_smile:
Diagnosing and Correcting TurboII Idle Problems
Over the time I have been involved with the Rx7 and TeamFC3S mailing lists, I have frequently heard complaints surrounding idle problems. Recently, I had my own run-in with idle problems and, with the help of Barrington Daltrey, a similarly afflicted member, learned a great deal about the idle circuit. Given the number of people who seem to encounter this problem, I would like to share what we learned with the rest of the Rx7 community. Given that most of our problems centered around the BAC valve, this writeup will likely be strongest in that area. There is still a lot we don't know, particularly as it relates to other Rx7 models and later years of the TII. Hopefully, those of you who have those cars can help us fill in the missing information.
Idle Circuit Theory of Operation
Hmmm... Where are my idle and fast idle set screws? The idle system on the 2nd generation RX7 consists of three electronically controlled solenoid valves. The Emissions Control Unit (ECU), which is really the engine management computer, controls the opening of these valves based on signals from the
- crank angle sensor
- throttle position sensor (TPS)
- water thermo sensor
- water temperature sensor
- intake air temperature sensor
- power steering sensor switch
- the air conditioner relay
- the initial set coupler
- Bypass Air Control (BAC) Valve - This valve controls the steady-state volume of air available to the engine when the car is idling. This effectively sets the idle speed.
- Air Supply Valve - This valve controls the flow of additional air at idle to compensate for the power requirements of the power steering pump when the wheels are being turned.
- Air Bypass Solenoid Valve - As far as I can tell, this valve provides the extra air required to create the extremely high idle speed when the car is started while cold. From what I have been able to gather from various literature, the purpose of this high idle speed is to speedily warm up the catalytic converters to operating temperature.
On Turbo II's, the BAC valve is located on the side of the intake manifold, above the turbo and Air Control Valve. It is a horizontal cylinder with a black plastic cap on the forward end. There are four hoses that connect to the valve. The two hoses that enter and exit parallel to the center axis of the valve are water hoses. The hose on the bottom is the air intake hose. The hose on the top is the air supply hose for the Air Bypass Solenoid valve.
The BAC valve is (unlike the other two valves) a variable valve whose opening is controlled by a duty cycle signal from the computer. This signal is a square wave with a variable duty cycle. The duty cycle of a square wave is the percentage of the time that the signal is in the "on" state vs. the total time to complete a cycle. The higher the duty cycle, the more power is transmitted to the device. This is depicted in Figure 1. The computer can increase the opening of the BAC valve, and thereby the engine speed, by increasing the duty cycle of the signal it sends to the BAC valve.
http://www.teamfc3s.org/info/pics/articles/figure1.jpg
All three of these valves are controlled by "open collector" transistor outputs. In this configuration, the transistor is a simple switch connected between the device and ground. The circuit and the equivalent circuit are depicted in Figure 2. When the transistor gets a positive signal voltage from the computer, it conducts and the circuit is completed through the solenoid to ground. This creates an opening force on the valve.
In the case of the BAC valve, the switch is opening and closing 125 times per second (125 Hz). This means that a complete cycle takes 8 mS. With the AC off, the transistor is "on" for about 2.4 mS which gives a duty cycle of 30%. When the AC is turned on, it requires a significant amount of aditional power from the engine. As many 2nd gen owners have experienced, if something isn't done to increase the air available at idle, the engine will die. The ECU senses that the AC is on by monitoring the signal from the AC compressor clutch. When it is engaged, the "on" time of the signal to the BAC valve is increased to 5.2 mS, which brings the duty cycle up to 65%. More power is transmitted to the BAC valve and the idle speed increases to compensate for the power loss to the compressor.
The idle adjust screw appears to control the quantity of air that flows through a bypass passage around the BAC valve.
Air Supply Valve
The Air Supply Valve is located near the firewall on the rear side of the intake manifold. It is a simple on/off valve that, when on, supplies a metered quantity of air to the engine to compensate for the power requirements of the power steering pump. The ECU turns it on when it sees a signal from the power steering switch on the power steering pump. Again, it is an "open collector" circuit.
If you notice a significant dip in your idle speed when you turn the steering wheel, something is wrong in the Air Supply Valve circuit. Given the location of the thing, it is going to be a bear to replace.
Notice the warning in the manual "Do not tamper with the adjust screw." Hah!
Air Bypass Solenoid Valve
The Air Bypass Solenoid Valve is the valve on top of the intake manifold on the passenger side of the intercooler. Above and slightly behind the BAC valve. It is a simple on/off valve that, when on, supplies the additional air required to create that high idle on cold start. It is in series with the BAC valve, so if the BAC valve is not opening correctly, the fast idle will not occur.
Summary
One has to wonder: "Why the complexity?". The function of all three valves could have been covered by the BAC valve alone, probably by simply changing software. This would have significantly reduced the complexity of the ECU electronics as well as the number of hoses running around.
Barrington Daltrey and I have discussed the possibility of creating an add-on circuit which takes the approach of monitoring the engine speed directly and changing the opening of the BAC valve accordingly. This would have the affect of compensating for any change in load (whether it be AC, power steering, or that killer stereo and alternator you want to install). I believe in this idea enough that I have started designing such a circuit. More on that in the future.
Anyway, all these components provide plenty of things to go wrong with the your car's idle quality.
Diagnosing Turbo II Idle Problems
There are a variety of possible failure modes in the idle circuit. This writeup describes trouble-shooting to identify the most common causes of problems. The first five items thoroughtly check the idle control loop, centered on the BAC control circuit. The shop manual adequately describes how to check the other components and sensors. The next few items give a couple of other things that can be checked and, finally, help is offered in case the ECU is found to be defective.
Symptoms:
- Car idles at about 600 RPM.
- Idle can not be increased with idle speed screw.
- Car frequently dies when AC is on.
- Disconnecting BAC valve connector (as per shop manual) does not change idle.
- Extreme hot starting problems.
1. Check to see if a jumper has been left in the initial set connector. It's easy to forget to remove this after adjusting idle speed. On '87-'88 models, the initial set connector is a green connector with two female spade connectors in it, placed at right angles to each other. It is located in the engine compartment, forward on the driver's side, near the headlight. On later models, it is a single conductor connector, located in about the same position. In these models, a jumper is connected between the connector and ground.
2. Check the Throttle Position Sensor setting. A variety of instructions for doing this are contained in the FAQ. My personal favorite is the two light bulbs. After setting it, rev the engine a couple of times to let everything settle back into place, and re-check it. You may even want to take the car for a quick drive and re-check the setting. An incorrectly set TPS seems to be the most frequent idle culprit. Make sure you get it right.
If you are still having problems, you probably have some kind of component failure. The tests now get a little more sophisticated.
3. Turn off the ignition. Remove the connector from the BAC valve and check the resistance of the BAC valve solenoid. This is done by connecting an ohm-meter across the BAC valve terminals. Care must be taken not to let the probes touch each other or you will get a false reading. You should get somewhere between 10 and 20 ohms. The manual says 10.7 to 12.3 ohms, but it's really not that picky. What you don't want is near zero ohms (solenoid is shorted) or very high resistance (solenoid is open-circuit.) If you have a shorted or open-circuit solenoid, you will need to replace the BAC valve. You might want to try disassembling it just on the off chance that it is repairable.
4. With the connector still removed, and the engine still off, place a 10k ohm, 1/4 watt resistor across the terminals of the connector. This is easy to do, simply insert the resistor leads into the connector. Make sure that the leads of the resistor do not short against each other or anything else. Turn the ignition on, without starting the car, and measure the AC voltage across the resistor. You should get a value between 6 and 7 volts after it settles down. A voltage lower than 5V indicates a likely ECU failure. Go here for more information. If you get the correct voltage, move on to the next step.
NOTE: This is a good chance to check that the conductors in the connector are firmly seated. Mine came loose, slid down, and shorted out, causing ECU failure. More on that in a moment. At the very least, if they are sliding around, they aren't making good contact. If you find that the conductors are loose in the connector, press the wires from the back of the connector towards the front. They should snap into place and not slide back. If they do slide back, you will need to either get a new connector, or epoxy them in, like I did. It works. (Be careful not to get epoxy on the connector surfaces!)
NOTE: Do not perform the following test if you obtained a reading of 0 ohms (short circuit) when you measured the resistance of the solenoid above. Something will get *very* hot.
5. The BAC valve may be stuck. Using jumper wires, connect 12V across the solenoid leads, being extremely careful not to create a short. If you didn't get an open-circuit reading when you measured the resistance of the BAC valve, the valve should click. If it is stuck, doing this a couple of times should free up the valve. I would also recommend removing the BAC valve from the intake manifold (this can be accomplished without removing the water hoses connected to the valve) and spraying WD-40 into it. Work it a few more times with 12V. If you can't get the thing to click this way, replace the BAC valve.
If you got to this point and you are still having idle problems, the problem is not in the electronic idle control system. Here are a few other possibilities and a few ways to check them:
1. Vacuum Leak
Vacuum leaks are frequently the cause of rough idle. A leak ruins your idle by allowing un-metered air to enter the intake manifold, creating a lean air-fuel mixture. Leaks typically develop as a result of vacuum or pressure hoses coming loose or failing, or gasket failures.
Vacuum leaks are frequently diagnosed and located by spraying some kind of flammable substance around the engine. When the flammable substance is sucked in through the leak, the lean condition is temporarily rectified and the engine will speed up. As can be imagined, spraying flammable substances around hot, running engines is a potentially very dangerous practice. It may best be left to qualified service personnel. "Poof, no eybrows!!" I don't even want to suggest flammable substances that can be used here.
A safer method that I have sometimes used successfully is to use a mechanic's stethoscope or a piece of vacuum tubing stuck in your ear. Use the other end to probe around the engine, listening for a hissing or whistling noise. I have successfully found both vacuum and exhaust leaks using this method.
2. Leaks in Intake Hoses
Leaks in the intake hoses after the Mass Airflow Sensor can result in bad idle in exactly the same manner as the vacuum leak. Again, the problem is unmetered air entering the engine. The best way to find these is simply by inspecting all of the components between the MAF and the throttle body.
On a TII, the problem is frequently the hose that connects the MAF to the turbo inlet. This hose has a tendancy to split, which lets air pass. A very small split can cause pretty big problems. Splits can sometimes be fixed with some RTV, but you need to be careful not to let the stuff get into the turbo. Also, make sure you use sealant that is O2 sensor safe. If you can afford it, or have access to a good used, hose, replace it.
3. Obstructed Exhaust System At least one Rx7 list contributor has had problems with his idle as a result of plugged catalytic converters.
This little article curtosy of Team FC3S. Thanks.:regular_smile:
yea man
hopefully i can get my runin finished by thn man haha
tong jin roy and yr ride damn nice man
next time i go outing with u guys must park one side liao
bro u been to guna's ? was thinking of going there to take a look... u interested in going together ?
hopefully i can get my runin finished by thn man haha
tong jin roy and yr ride damn nice man
next time i go outing with u guys must park one side liao
bro u been to guna's ? was thinking of going there to take a look... u interested in going together ?
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