Idle Air control Valve - help
05-20-20, 01:27 AM
#1
Full Member
Thread Starter
Idle Air control Valve - help
I got my car tuned last week and it made a respectable 330 wheel on e85 on 10 lbs of boost. The dyno went really well considering the car was "built" 11 years ago and was neglected all its life. I know the compression is on the low side but it doesnt smoke, it is very difficult to start when cold, but other then that it fires up when its warm or been running once in the day.
I ran into 2 other small issues, 1 was a fuel pressure drop, and with the pump and injectors, those weren't the cause. It turned out to be a bad Fuel dampener from Radium.
And the other issue that I am finding quite irritating is I was told the Idle air control valve was not working. I have a brand new dash pot on the TB but anytime I get off the throttle the car dies. If I give it a little blip as the rpms are falling off it will recover idle, but I assume the Idle air control valve is the reason for this.
Further I did some testing. I put 12volt to the IACV and it actuates, so then I tested the harness and I get NO power on either pins. It appears the harness may be damaged somewhere. Being that electronics are my weakest skill, if you throw a "shop manual" at me with electrical schematics I promise you I will not be able to decript it.
So my question is this, If the harness is damaged, and I dont doubt that, it was in really rough shape, Is there a way I can supply 12v and also the ground to what controls the IACV. I am thinking if I can just make a new harness it would be a lot easier then trying to chase where the stock one is damaged.
Truthfully the entire engine harness needs to be replaced. The injectors wires have lots of bare wires and most of the insulation is hard and brittle. But without focusing on that, any suggestions to get the IACV functioning so I can see if thats the correct fix?
Some dyno video for fun!
I ran into 2 other small issues, 1 was a fuel pressure drop, and with the pump and injectors, those weren't the cause. It turned out to be a bad Fuel dampener from Radium.
And the other issue that I am finding quite irritating is I was told the Idle air control valve was not working. I have a brand new dash pot on the TB but anytime I get off the throttle the car dies. If I give it a little blip as the rpms are falling off it will recover idle, but I assume the Idle air control valve is the reason for this.
Further I did some testing. I put 12volt to the IACV and it actuates, so then I tested the harness and I get NO power on either pins. It appears the harness may be damaged somewhere. Being that electronics are my weakest skill, if you throw a "shop manual" at me with electrical schematics I promise you I will not be able to decript it.
So my question is this, If the harness is damaged, and I dont doubt that, it was in really rough shape, Is there a way I can supply 12v and also the ground to what controls the IACV. I am thinking if I can just make a new harness it would be a lot easier then trying to chase where the stock one is damaged.
Truthfully the entire engine harness needs to be replaced. The injectors wires have lots of bare wires and most of the insulation is hard and brittle. But without focusing on that, any suggestions to get the IACV functioning so I can see if thats the correct fix?
Some dyno video for fun!
05-20-20, 08:12 AM
#2
RX-7 Bad Ass
iTrader: (55)
When you are at idle, is the idle solid at the correct RPM? Does the idle compensate for load - turn on the defroster, turn on AC, the idle stays good or comes up a bit?
Stalling when coming to a stop is almost always going to be the dashpot. It's super easy to test - push down on the plunger and it should be hard to push in and slow to go all the way in. If it just pops in and out it's dead and needs to be replaced.
Also could be the dashpot is good but needs to be adjusted.
The ISC isn't an on/off valve. The ECU sends a duty cycle - pulses - to the ISC. Fewer pulses, it's more closed, more pulses, it's more open. That's near impossible to see on a multimeter, you would need an oscilloscope to see that. But typically you don't have to go that far, the ISC is a pretty simple system and generally just works. If your car is holding a good idle it's probably OK.
What ECU are you running?
Dale
Stalling when coming to a stop is almost always going to be the dashpot. It's super easy to test - push down on the plunger and it should be hard to push in and slow to go all the way in. If it just pops in and out it's dead and needs to be replaced.
Also could be the dashpot is good but needs to be adjusted.
The ISC isn't an on/off valve. The ECU sends a duty cycle - pulses - to the ISC. Fewer pulses, it's more closed, more pulses, it's more open. That's near impossible to see on a multimeter, you would need an oscilloscope to see that. But typically you don't have to go that far, the ISC is a pretty simple system and generally just works. If your car is holding a good idle it's probably OK.
What ECU are you running?
Dale
05-20-20, 09:38 AM
#3
Full Member
Thread Starter
When you are at idle, is the idle solid at the correct RPM? Does the idle compensate for load - turn on the defroster, turn on AC, the idle stays good or comes up a bit?
Stalling when coming to a stop is almost always going to be the dashpot. It's super easy to test - push down on the plunger and it should be hard to push in and slow to go all the way in. If it just pops in and out it's dead and needs to be replaced.
Also could be the dashpot is good but needs to be adjusted.
The ISC isn't an on/off valve. The ECU sends a duty cycle - pulses - to the ISC. Fewer pulses, it's more closed, more pulses, it's more open. That's near impossible to see on a multimeter, you would need an oscilloscope to see that. But typically you don't have to go that far, the ISC is a pretty simple system and generally just works. If your car is holding a good idle it's probably OK.
What ECU are you running?
Dale
Stalling when coming to a stop is almost always going to be the dashpot. It's super easy to test - push down on the plunger and it should be hard to push in and slow to go all the way in. If it just pops in and out it's dead and needs to be replaced.
Also could be the dashpot is good but needs to be adjusted.
The ISC isn't an on/off valve. The ECU sends a duty cycle - pulses - to the ISC. Fewer pulses, it's more closed, more pulses, it's more open. That's near impossible to see on a multimeter, you would need an oscilloscope to see that. But typically you don't have to go that far, the ISC is a pretty simple system and generally just works. If your car is holding a good idle it's probably OK.
What ECU are you running?
Dale
The idle will hold steady after 3-4 minutes after starting it, then it starts to drop rpms, and it will begin a drop and recovery until it drops too the point it wont recover. It's like when the car starts getting warm this begins to happen. I wont call it a surge because a surge to me a gain on rpms.
The strange thing here is once the car is full temp this seems to go away, almost like it's in a second stage of warm up idle.
Its using a power fc. They had it idling around 750-850 and it will hold idle but I move it up to 900 to try to alleviate the stall condition and it didnt help, like I mentioned it's just when the th closes the car will stall without a little blip of throttle manually input by me.
05-21-20, 04:17 PM
#4
Full Member
Thread Starter
does 4Q look like the correct pin for the IACV pinout. googling rx7 fd3s ecu pinout is giving me multiple different ecu layouts.
https://www.flickr.com/photos/63733846@N00/20629362038
https://www.flickr.com/photos/63733846@N00/20629362038
05-21-20, 04:22 PM
#5
RX-7 Bad Ass
iTrader: (55)
Look in the shop manual, that has all you need to know on the wiring.
If you have a PowerFC the coolant map may be off or something if it's stalling when warming up. May want to research that.
Dale
If you have a PowerFC the coolant map may be off or something if it's stalling when warming up. May want to research that.
Dale
The following users liked this post:
Tyler Twerdun (05-21-20)
05-22-20, 08:15 AM
#6
I also tune Rx7’s. The dash pot does little to nothing. What catches rpm is the iacv. You need this working to catch the idle. The iacv is like blipping the throttle for you. You also need the iacv for starting the car otherwise you may need to blip the throttle at start up.
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Tyler Twerdun (05-22-20)
05-22-20, 02:15 PM
#7
Full Member
Thread Starter
I also tune Rx7’s. The dash pot does little to nothing. What catches rpm is the iacv. You need this working to catch the idle. The iacv is like blipping the throttle for you. You also need the iacv for starting the car otherwise you may need to blip the throttle at start up.
Sounds like I'm on the right track. Cold starts are horrible lol
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05-28-20, 10:14 AM
#8
The Idle Air Control Valve should receive 12V power on the B/W wire (black with white stripe) wire, and then the ECU will send ground to close it. The ECU doesn't simply connect it to ground, it will use a high-speed duty cycle and the DC voltage you can measure with a multimeter will be something between 1V and 12V.
There are two ways you can test the IACV.
1a. With the key off and battery disconnected, use the multimeter (and some extra length of wire) to check continuity between the B/W pin on the IACV connector and the EGI Main Relay connector (in the fuse block under the hood). From what I'm seeing this looks like it would be pin 3 on the relay, but if the relay is unplugged and battery is disconnected there should be no harm in checking connectivity to all four pins of the relay. It will only be connected to one of the four pins. Some of the B/W wires are daisy-chained in the harness, it's a relatively common problem for people to accidentally disconnect the IACV power when removing other rats-nest solenoid connectors to 'simplify' their harness.
1b. The L/G (blue with green stripe) wire from the IACV should have connectivity to pin 4Q on the ECU. Pin 4Q is on the largest plug, note there are other L/G colored wires on other ECU plugs and there are lots of other blue wires (with various stripe colors) on the same plug as 4Q.
2a. Continuity is nice but the IACV works because of electrical power going through it, current and voltage. It's pretty easy to check voltage with the key on. The B/W pin should have 12V when the key is on. Red probe of the multimeter should go to the B/W pin (use a short length of wire if the tip of the multimeter probe is too thick to touch the pin inside the connector), and black probe of the multimeter can get grounded to any bolt on the chassis or engine. You can check this with the IACV unplugged.
2b. It's harder to check voltage at the L/G pin of the IACV, because it needs to be plugged in to check properly. The bad way to check is to pierce the wire so you can measure the voltage inside it, try to avoid this because piercing the wire can cause short circuits later. The better way is to insert a very thin piece of metal (T-clip, sewing needle, paper clip, welding rod) where the wire goes into the connector, so that metal touches the back of the pin. This is called 'back probing', good video example here:
When back probing the L/G wire with the key on, voltage should be somewhere between 1V - 12.0V when the engine is running. I would be surprised to see exactly battery voltage at both the L/G wire and the B/W wire, that is a good sign the L/G wire doesn't actually connect to the ECU or there's a fault inside the ECU.
Good luck,
-s-
There are two ways you can test the IACV.
1a. With the key off and battery disconnected, use the multimeter (and some extra length of wire) to check continuity between the B/W pin on the IACV connector and the EGI Main Relay connector (in the fuse block under the hood). From what I'm seeing this looks like it would be pin 3 on the relay, but if the relay is unplugged and battery is disconnected there should be no harm in checking connectivity to all four pins of the relay. It will only be connected to one of the four pins. Some of the B/W wires are daisy-chained in the harness, it's a relatively common problem for people to accidentally disconnect the IACV power when removing other rats-nest solenoid connectors to 'simplify' their harness.
1b. The L/G (blue with green stripe) wire from the IACV should have connectivity to pin 4Q on the ECU. Pin 4Q is on the largest plug, note there are other L/G colored wires on other ECU plugs and there are lots of other blue wires (with various stripe colors) on the same plug as 4Q.
2a. Continuity is nice but the IACV works because of electrical power going through it, current and voltage. It's pretty easy to check voltage with the key on. The B/W pin should have 12V when the key is on. Red probe of the multimeter should go to the B/W pin (use a short length of wire if the tip of the multimeter probe is too thick to touch the pin inside the connector), and black probe of the multimeter can get grounded to any bolt on the chassis or engine. You can check this with the IACV unplugged.
2b. It's harder to check voltage at the L/G pin of the IACV, because it needs to be plugged in to check properly. The bad way to check is to pierce the wire so you can measure the voltage inside it, try to avoid this because piercing the wire can cause short circuits later. The better way is to insert a very thin piece of metal (T-clip, sewing needle, paper clip, welding rod) where the wire goes into the connector, so that metal touches the back of the pin. This is called 'back probing', good video example here:
Good luck,
-s-
The following 2 users liked this post by scotty305:
EZAS (11-29-22),
Tyler Twerdun (05-28-20)
08-14-20, 08:21 PM
#9
The Idle Air Control Valve should receive 12V power on the B/W wire (black with white stripe) wire, and then the ECU will send ground to close it. The ECU doesn't simply connect it to ground, it will use a high-speed duty cycle and the DC voltage you can measure with a multimeter will be something between 1V and 12V.
There are two ways you can test the IACV.
1a. With the key off and battery disconnected, use the multimeter (and some extra length of wire) to check continuity between the B/W pin on the IACV connector and the EGI Main Relay connector (in the fuse block under the hood). From what I'm seeing this looks like it would be pin 3 on the relay, but if the relay is unplugged and battery is disconnected there should be no harm in checking connectivity to all four pins of the relay. It will only be connected to one of the four pins. Some of the B/W wires are daisy-chained in the harness, it's a relatively common problem for people to accidentally disconnect the IACV power when removing other rats-nest solenoid connectors to 'simplify' their harness.
1b. The L/G (blue with green stripe) wire from the IACV should have connectivity to pin 4Q on the ECU. Pin 4Q is on the largest plug, note there are other L/G colored wires on other ECU plugs and there are lots of other blue wires (with various stripe colors) on the same plug as 4Q.
2a. Continuity is nice but the IACV works because of electrical power going through it, current and voltage. It's pretty easy to check voltage with the key on. The B/W pin should have 12V when the key is on. Red probe of the multimeter should go to the B/W pin (use a short length of wire if the tip of the multimeter probe is too thick to touch the pin inside the connector), and black probe of the multimeter can get grounded to any bolt on the chassis or engine. You can check this with the IACV unplugged.
2b. It's harder to check voltage at the L/G pin of the IACV, because it needs to be plugged in to check properly. The bad way to check is to pierce the wire so you can measure the voltage inside it, try to avoid this because piercing the wire can cause short circuits later. The better way is to insert a very thin piece of metal (T-clip, sewing needle, paper clip, welding rod) where the wire goes into the connector, so that metal touches the back of the pin. This is called 'back probing', good video example here: https://www.youtube.com/watch?v=g2ST8w_0w-Q
When back probing the L/G wire with the key on, voltage should be somewhere between 1V - 12.0V when the engine is running. I would be surprised to see exactly battery voltage at both the L/G wire and the B/W wire, that is a good sign the L/G wire doesn't actually connect to the ECU or there's a fault inside the ECU.
Good luck,
-s-
There are two ways you can test the IACV.
1a. With the key off and battery disconnected, use the multimeter (and some extra length of wire) to check continuity between the B/W pin on the IACV connector and the EGI Main Relay connector (in the fuse block under the hood). From what I'm seeing this looks like it would be pin 3 on the relay, but if the relay is unplugged and battery is disconnected there should be no harm in checking connectivity to all four pins of the relay. It will only be connected to one of the four pins. Some of the B/W wires are daisy-chained in the harness, it's a relatively common problem for people to accidentally disconnect the IACV power when removing other rats-nest solenoid connectors to 'simplify' their harness.
1b. The L/G (blue with green stripe) wire from the IACV should have connectivity to pin 4Q on the ECU. Pin 4Q is on the largest plug, note there are other L/G colored wires on other ECU plugs and there are lots of other blue wires (with various stripe colors) on the same plug as 4Q.
2a. Continuity is nice but the IACV works because of electrical power going through it, current and voltage. It's pretty easy to check voltage with the key on. The B/W pin should have 12V when the key is on. Red probe of the multimeter should go to the B/W pin (use a short length of wire if the tip of the multimeter probe is too thick to touch the pin inside the connector), and black probe of the multimeter can get grounded to any bolt on the chassis or engine. You can check this with the IACV unplugged.
2b. It's harder to check voltage at the L/G pin of the IACV, because it needs to be plugged in to check properly. The bad way to check is to pierce the wire so you can measure the voltage inside it, try to avoid this because piercing the wire can cause short circuits later. The better way is to insert a very thin piece of metal (T-clip, sewing needle, paper clip, welding rod) where the wire goes into the connector, so that metal touches the back of the pin. This is called 'back probing', good video example here: https://www.youtube.com/watch?v=g2ST8w_0w-Q
When back probing the L/G wire with the key on, voltage should be somewhere between 1V - 12.0V when the engine is running. I would be surprised to see exactly battery voltage at both the L/G wire and the B/W wire, that is a good sign the L/G wire doesn't actually connect to the ECU or there's a fault inside the ECU.
Good luck,
-s-
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