IAC restrictor plate installed!
- Thread starter R.J.
- Start date
-
Sponsors (?)
I found one, it must be the one I had in my car before I got it custom tuned. Just PM me your name and address and I will mail it to you.
DIRECTIONS:
This is for anyone that doesn't like when the RPM's that are slow to drop or even rise slightly when you push the clutch in to shift. Another symptom, is that when cruising in a higher gear and you let your foot off the gas, the car almost cruises on its own for a bit.
First, understand the problem. The engine is receiving too much air through the IAC valve. From my knowledge Ford did this for emissions reasons.
As a side effect of this fix, when you downshift, the car burbles a lot more, sounds like a carberated engine. You get a little more engine braking effect.
The FIX:
Most older mustangs have an external IAC valve. Meaning that it is easy to find, follow a small air hose (1/2" ID) to a silver cylinder thing on your intake (the IAC solenoid). Once you found it, the older fix was to buy a 1/2" copper pipe cap, drill out a small hole, insert this into the line the restrict air flow through the IAC, and your done.
The Mach has a slightly different setup.
We have an INTERNAL IAC air supply. Meaning that there is no hose leading to it.
To find your IAC valve, first remove your entire shaker assembly from your car.
Next, look between your intake and the firewall, there should be a silver cylinder shaped object with 2 bolts leading to your intake.
Remove the two bolts and move this assembly.
You should see the following, the IAC assembly has two "ports" with the solenoid controlling the air flow between these two ports, what we want to accomplish is to restrict the airflow leading through this.
To do this, there should be a small gasket on your intake, or it could be stuck to the IAC valve.
Remove this (carefully)
Trace out the shape of this gasket as well as the holes for mounting bolts, and the two air holes, onto a piece of 1/32" aluminum or something similar.
Cut out the outline of this "restrictor plate" from the aluminum.
Cut out the holes for your bolts to go through.
Cut out a single one of the Air holes.
Now the tricky part. You have to decide how big to make the other hole because this determines the amount of air you are restricting.
The smallest you should go would be around 5/32", the worst case if you go to small is your car will stall when fix is complete, if this happens just take the plate out, make the hole bigger, and check that.
The hole I used is around 9/32" which is about the medium you would want to go.
After your "restrictor plate" is cut out, mount it with the small hole on the passenger side of the IAC, and make sure to replace the gasket against the intake.
Start your car, you should notice the RPMs drop when you start back to normal very quickly.
If it idles smoothly, try putting turning on the AC, this will load the engine down.
If your car stalls out, remove the plate, make the hole bigger, try again.
If still idling smoothly, bolt your shaker back on, take it for a spin. You might need to adjust your driving/clutching style after being used to the crappy RPM hang, so don't be discouraged.
Also, you might want to disconnect your battery during the procedure to make your computer relearn it tweaks after you finish.
If, after you start the car you notice a "whistling" sound, then take a look at your plate, make sure the BIG hole is at least as big as the hole on the IAC valve. Also make sure edges of holes are rounded (sharp edges are bad), and the holes are round. This happened on mine, and I fixed it.
This subject has been talked about on Stangnet and a search will give you more opinions. I love it!!!!!!!!
This is for anyone that doesn't like when the RPM's that are slow to drop or even rise slightly when you push the clutch in to shift. Another symptom, is that when cruising in a higher gear and you let your foot off the gas, the car almost cruises on its own for a bit.
First, understand the problem. The engine is receiving too much air through the IAC valve. From my knowledge Ford did this for emissions reasons.
As a side effect of this fix, when you downshift, the car burbles a lot more, sounds like a carberated engine. You get a little more engine braking effect.
The FIX:
Most older mustangs have an external IAC valve. Meaning that it is easy to find, follow a small air hose (1/2" ID) to a silver cylinder thing on your intake (the IAC solenoid). Once you found it, the older fix was to buy a 1/2" copper pipe cap, drill out a small hole, insert this into the line the restrict air flow through the IAC, and your done.
The Mach has a slightly different setup.
We have an INTERNAL IAC air supply. Meaning that there is no hose leading to it.
To find your IAC valve, first remove your entire shaker assembly from your car.
Next, look between your intake and the firewall, there should be a silver cylinder shaped object with 2 bolts leading to your intake.
Remove the two bolts and move this assembly.
You should see the following, the IAC assembly has two "ports" with the solenoid controlling the air flow between these two ports, what we want to accomplish is to restrict the airflow leading through this.
To do this, there should be a small gasket on your intake, or it could be stuck to the IAC valve.
Remove this (carefully)
Trace out the shape of this gasket as well as the holes for mounting bolts, and the two air holes, onto a piece of 1/32" aluminum or something similar.
Cut out the outline of this "restrictor plate" from the aluminum.
Cut out the holes for your bolts to go through.
Cut out a single one of the Air holes.
Now the tricky part. You have to decide how big to make the other hole because this determines the amount of air you are restricting.
The smallest you should go would be around 5/32", the worst case if you go to small is your car will stall when fix is complete, if this happens just take the plate out, make the hole bigger, and check that.
The hole I used is around 9/32" which is about the medium you would want to go.
After your "restrictor plate" is cut out, mount it with the small hole on the passenger side of the IAC, and make sure to replace the gasket against the intake.
Start your car, you should notice the RPMs drop when you start back to normal very quickly.
If it idles smoothly, try putting turning on the AC, this will load the engine down.
If your car stalls out, remove the plate, make the hole bigger, try again.
If still idling smoothly, bolt your shaker back on, take it for a spin. You might need to adjust your driving/clutching style after being used to the crappy RPM hang, so don't be discouraged.
Also, you might want to disconnect your battery during the procedure to make your computer relearn it tweaks after you finish.
If, after you start the car you notice a "whistling" sound, then take a look at your plate, make sure the BIG hole is at least as big as the hole on the IAC valve. Also make sure edges of holes are rounded (sharp edges are bad), and the holes are round. This happened on mine, and I fixed it.
This subject has been talked about on Stangnet and a search will give you more opinions. I love it!!!!!!!!
That is the install directions and this is the idle reset directions.
Try resetting your idle with the following procedure. If your idle problem is NOT being caused by a bad part or vacuum leak then I have never seen this not fix the problem!
Begin with a cold vehicle. The idea here is to get the car to a firm cold idle with enough air bleed capacity left in the idle circuit for IAC adjustment.
The idle stop should be set first. Back out the idle stop screw, away from the bell crank arm, until about 1/2 turn past the point where it no longer makes contact (blade fully closed). Using a 0.010" feeler gauge, tighten until gauge just drags between screw and bell crank arm. Remove feeler gauge. Tighten screw exactly 1 1/2 turns. If the screw is very loose, put a drop of loc-tite or silicone on it, so it doesn't work out of adjustment.
Now remove the connector to the Idle Air Controller (IAC) just on the other side of the throttle body. Start the car and allow vehicle to warm for 2 minutes. Give a small "blip" to let it settle. If it is having a hard time staying running you may have to get an assistant until you can get to the front of the car. Now open or close the air bleed screw (CCW opens) next to the IAC until the car idles at 575 to 600 rpm. For guys with aftermarket cams and an EEC tuner, you might want to idle a bit more briskly, say 650 to 675.
Obviously, this rpm range is by what the car and driver wants...IE, no set idle speed, whatever works for YOU.
Turn off the car. Now count the number of turns clockwise to close on the idle air bleed screw. If it falls between 1/2 and 2, it's okay, now reverse it out the same number of turns. Log the number somewhere in case you need it for the future. Reconnect the IAC. You are done.
If the air bleed screw is above 2 turns, it's a good idea to tighten the idle stop screw another 1/2 turn, and then repeat the idle setting. If it is below 1/2 turn, then loosen the idle stop screw by 1/4 to 1/2 a turn, and repeat the idle setting. Be sure to put another drop of silicone RTV on the stop screw if it was disturbed. Reconnect the IAC.
Now remember we adjusted the set screw on the throttle body. That means that the voltage reading from the TPS sensor has changed. It should read between .96 and .99 volts. Anything outside of that range will cause all sorts of issues including misfires and rough idle.
you will have to back probe the TPS connector. With the connector attached to the TPS stick a paper clip into the rubber boot on the connector where the top and middle wires go into the connector. The rubber is very flexible the paper clip will slide in between the rubber and the wire.
Set your multimeter to volts. Turn ignition to ON. Then place your multimeter leads on the metal pins. If it comes up as a negative that is okay as long as you are -.96 to -.99. If you get this reading then great you are done and hopefully your issues are gone. If not proceed to step 9
This is where and extra pair of hands come in handy. Using a large screw driver you will need to loosen the bolts that hold the TPS. DO NOT USE A SCREWDRIVER THAT IS TOO SMALL BECAUSE YOU WILL STRIP THE BOLTS. They probably will be really tight so you have to really lean on the screwdriver and use some finesse.
Once the bolts are loose you will need to move the TPS up or down and continue to read the voltage. Once you get it to the desired setting you can retighten the bolts. What I do is I find .97 and then as carefully as possible I tighten the TPS down. what will happen is the voltage will change usually to .96 or .98 but that it okay. Once you are done with this manually open the throttle body a few times and close it then reread the voltage and make sure it is still within our desired range.
Depending upon how loose your set screw was you might want to cover it in RTV to hold your setting. At this point you have CORRECTLY reset you idle.
Try resetting your idle with the following procedure. If your idle problem is NOT being caused by a bad part or vacuum leak then I have never seen this not fix the problem!
Begin with a cold vehicle. The idea here is to get the car to a firm cold idle with enough air bleed capacity left in the idle circuit for IAC adjustment.
The idle stop should be set first. Back out the idle stop screw, away from the bell crank arm, until about 1/2 turn past the point where it no longer makes contact (blade fully closed). Using a 0.010" feeler gauge, tighten until gauge just drags between screw and bell crank arm. Remove feeler gauge. Tighten screw exactly 1 1/2 turns. If the screw is very loose, put a drop of loc-tite or silicone on it, so it doesn't work out of adjustment.
Now remove the connector to the Idle Air Controller (IAC) just on the other side of the throttle body. Start the car and allow vehicle to warm for 2 minutes. Give a small "blip" to let it settle. If it is having a hard time staying running you may have to get an assistant until you can get to the front of the car. Now open or close the air bleed screw (CCW opens) next to the IAC until the car idles at 575 to 600 rpm. For guys with aftermarket cams and an EEC tuner, you might want to idle a bit more briskly, say 650 to 675.
Obviously, this rpm range is by what the car and driver wants...IE, no set idle speed, whatever works for YOU.
Turn off the car. Now count the number of turns clockwise to close on the idle air bleed screw. If it falls between 1/2 and 2, it's okay, now reverse it out the same number of turns. Log the number somewhere in case you need it for the future. Reconnect the IAC. You are done.
If the air bleed screw is above 2 turns, it's a good idea to tighten the idle stop screw another 1/2 turn, and then repeat the idle setting. If it is below 1/2 turn, then loosen the idle stop screw by 1/4 to 1/2 a turn, and repeat the idle setting. Be sure to put another drop of silicone RTV on the stop screw if it was disturbed. Reconnect the IAC.
Now remember we adjusted the set screw on the throttle body. That means that the voltage reading from the TPS sensor has changed. It should read between .96 and .99 volts. Anything outside of that range will cause all sorts of issues including misfires and rough idle.
you will have to back probe the TPS connector. With the connector attached to the TPS stick a paper clip into the rubber boot on the connector where the top and middle wires go into the connector. The rubber is very flexible the paper clip will slide in between the rubber and the wire.
Set your multimeter to volts. Turn ignition to ON. Then place your multimeter leads on the metal pins. If it comes up as a negative that is okay as long as you are -.96 to -.99. If you get this reading then great you are done and hopefully your issues are gone. If not proceed to step 9
This is where and extra pair of hands come in handy. Using a large screw driver you will need to loosen the bolts that hold the TPS. DO NOT USE A SCREWDRIVER THAT IS TOO SMALL BECAUSE YOU WILL STRIP THE BOLTS. They probably will be really tight so you have to really lean on the screwdriver and use some finesse.
Once the bolts are loose you will need to move the TPS up or down and continue to read the voltage. Once you get it to the desired setting you can retighten the bolts. What I do is I find .97 and then as carefully as possible I tighten the TPS down. what will happen is the voltage will change usually to .96 or .98 but that it okay. Once you are done with this manually open the throttle body a few times and close it then reread the voltage and make sure it is still within our desired range.
Depending upon how loose your set screw was you might want to cover it in RTV to hold your setting. At this point you have CORRECTLY reset you idle.
i have read that the idle hanging when stopping at light is in comp.also it has a retard during shift with idle staying up for people that cant drive standard very good.i really hate this also i have a 95 with a sc/tfs stage 3 tw/c/i i love the sound but hate the way when you rev it ,it takes forever to idle down(compared to my 89 that had a 550 lift crane cam}.i would love to cure this problem i need a tune but this thing has run so good at times makes me think its not all in the tune i have looked for vac.leaks.i have intake off right now replacing all vac. lines.thanks for the pics it helped out.i just deleted my egr(by lanking off at elbo and taking head off valve compressing plunge half way)i could see the exaust fumes where they entered my intake not good for hp my sc puts out enough heat just someting else for yall to think about
Similar threads
