Hey, my idle has been off since the day I got my FC. I have dealt with it since I got the car and finally decided that I need to fix it for gas mileage and other reasons.
It mainly does this when it is cold and surges a bit from like 1500-1700. I have tried everything and noticed that if I unplug the BAC then it doesn't change a bit. I noticed there is a pipe running off of it and the car will not rev past 3000 whenever it isn't plugged.
When the car warms up it usally idles at about 1,000.
If I can get information on adjusting these things and what might fix my idle then I would greatly appreciate it. I will give any information needed and will show you plenty of pictures.
I can try and upload a video soon. The tape is only on that tube to hold the plug in. I don't want to risk it falling out because it done has before.
Also my throttle cable is a little too lose.
Thanks!

Pictures:

 

Bump. Help please.

 

What is the duct tape for?

 

bump, i have the EXACT same problem, cant figure it out. i changed the bacv and didnt help. i think it might be the tps, so thats getting changed next. o have you tried to use lights to tune the tps?(by connecting them to the plug by the passanger side front strut?) i tried this and im only getting one light.

 

You're only supposed to get one light. Two of the wires running to the LED lights come from the Switching and Relief solenoid and only one of them should be activated when the car is idling and fully warmed up and that would be the Relief solenoid thus only one light is supposed to turn on.

 

I mentioned in my post the tape was to be sure the plug stays in. The car will not rev over 3000rpm if the plug falls out which happened before. I don't want to lose the plug so the tape is just there until I come up with a more permanent solution. I am gonna do a resistance check on my tps whenever I get a a dmm.

 

The hose you have taped should run to the underside of the intake duct. Does the underside of the intake also have tape on it as well or is it open?

 

in the picture it looks like its aftermarket so im probably sure that there is not a location for it on the intake.

 

Yes it is an aftermarket intake duct.


Should I run that hose to the intake duct somewhere? Or is it just not important?

 

The role of the BAC is to supply additional air into the throttle body when the car is under load related to things such as the A/C turned on or the headlights turned on or power steering is used. If not for the BAC, the idle speed set at the factory would drop below 750 rpm and it is the BAC's responsibility to prevent this from happening. The BAC also assists in the starting of the car as it works to its maximum potential in this situation to allow more air to be injected into the throttle body. Thus the BAC cannot work at all w/the way you have the hose plugged up unless the plug leaks some air into the hose that leads to the BAC.

When the engine is thoroughly warmed up it should idle at 750 to 800 rpm. There is an idle adjust screw located on top of the throttle body which helps to set the idle. The Initial Set Coupler needs to be jumpered before adjusting this particular screw.

On an S4 there is the Variable Resistor which can also help to alter the idle a smidgeon as well.

When the the car is idling as low as it will drop to you could press upward on the throttle linkage at the front of the throttle body to check to see if the idle speed drops further. If it does then there is something causing the primary throttle plates to open a bit too much.

Your fabricated intake duct needs to be free of air leaks as well.

 

The car has neither a/c nor p/s. It has the bear essentials (FD alternator and water pump) so it shouldn't be much of a problem the way it is.

I have tried setting the idle with the idle scew and pushing up on the throttle linkage and neither make a difference. Like I mentioned the throttle cable is a little too loose.

The intake duct is free of leaks. The problem is a high idle which usually drops to about 1,000 with no bounce when the car is warm (But takes like 30 minutes of driving for this to happen). When you first start the car on a cold/damp morning is when it idles at 1500 with a constant bounce.

Soon I will check/adjust the TPS. If someone could tell me which screw to adjust for that or even where its at I would greatly appreciate it. I have an idea where the tps is, but all the info I can find is on a turbo II engine.

 

Even if you turn the fan on it will want to drop the idle. Also, if the BAC is stuck open some then it will add the additional air and would boost the idle speed. This is just a possible cause of a high idle,but there needs to be air feeding to the BAC for this to occur.

The second pic of the throttle body illustrates the TPS screw in front of the TPS and this screw is encased in a spring. The idle needs to be as low as it will go before adjusting it and it will affect a bouncing idle but not the speed of the idle necessarily. You backprobe the G/R wire w/key to on and engine fully warmed before adjusting the screw. The timing of the car advances when above 1100 rpm or so and setting the TPS at this speed or higher is inefficient. The G/R wire is to be 1 volts as stated in the FSM.

Again, the Initial Set Coupler needs to be jumpered before adjusting the screw on top of the throttle body. In your case this may not be needed because doing this affects the BAC but if yours is inoperable then it won't be necessary to jumper the coupler "unless there is a leak of air in the hose you have tried to plug up."

Also, it appears your AFM is on its side and normally it needs to lay flat on its tummy and level as well.

And the Variable Resistor has some affect on the idle speed.

And low voltage can affect the operability of the engine components which are electrically related.

 

I will be sure to check all of these things soon whenever its not raining out. Thank you for the information so far. You have been very thorough and helpful. I hope I can figure this out soon. I will keep you updated!

 

One other thing. In the first pic there are two screws pictured as one is in the center of the throttle body and this is the idle adjust screw while the screw located at the edge of the throttle body closest to the front is for setting the secondary plates. This screw needs to be fully screwed in "if it is the factory screw that came w/the car as it rolled off the factory line." The lever underneath it is associated w/the secondary plates and should rest upon the bottom of the screw. If the screw is too long (not factory standard) and sticks out the bottom too much then it would cause a higher than normal idle.

 

I think you may have found my high idle problem but I'm not sure about the surging idle. Could be that its hitting that limit where the timing changes I guess?
Is this the screw you mean?

 

Alright maybe I read that wrong. I'll try to loosen the screw and see what it does though.

 

Yes, that is the screw.

 

And the screw to the right and down a little from that one is the tps adjustment?

 

Yes.

 

Thanks! I'll try some adjusting after class tomorrow.

 

I made it home from class today with my car warm and the idle was a steady 1500 which is much too high. I noticed the screw could be turned in or out and if i turned it out the plate didn't contact the screw anymore but when I turned it in a little to correct the problem the idle started surging again. That kinda of gives me an idea that the surge could be because of the secondary plate.

Is there any fix I can do to fix this? Maybe something else that is associated with the secondary plates. I did try moving the lever up towards the screw but it was all the way up.

 

Your fast idle cam might be causing you problems as when the cam fully rolls off of the pin it should cause the primary throttle plates to close almost completely and thus reduce the idle speed. With the intake tube disconnected from the throttle body the primary plates will appear to be fully closed but are rather slightly opened. If the gap is more than a couple of hundreths of an inch then something is causing them not to close properly. Carbon build up could do this. If the plates are as they are supposed to be then the fast idle cam not rolling off of the set pin completely could cause the primary plates to be open too much. There is also a screw on the back of the throttle body that sets how much the primary throttle plates will close but this screw is hard to access w/o removing the throttle body if I remember correctly.

 

I have checked the throttle body and it is all clean. I don't have a feeler gauge but just from sight it looks to be right.
Whats this pin though?
I think I can get a screw driver in there to adjust the screw. Should I try this or leave it alone. How should it be adjusted?

 

If the primary plates look as they should then adjusting the set screw is not needed.

The Fast Idle Cam is on the back of the throttle body hidden behind the dashpot. The cam rolls off of a metal pin (end is painted Green) as the coolant heats up and removes the fast idle mechanism from doing its job of keeping the idle high as the engine initially warms up. Using the advanced search feature will provide you with pics. Post #79 etc. shows the necessary pics.

https://www.rx7club.com/showthread.p...le+pics&page=4

If air is leaking to the BAC and it is opened (BAC) then it will cause the idle to rise. You might want to disconnect the two wire plug to the BAC to see if there is any change.

Besides the throttle cable there is a cruise control cable and if equipped this would cause a higher than normal idle if it is too tight.

And if your throttle body has been modified then it could cause a higher idle.

 

Primary screws look great and the dashpot seems to be functional but the white part on it is always showing. I never seen a green pin when i checked. I would actually like to disable the accelerated warm up and have it when the cam is always off of the pin if that is possible?

I unplugged the bac and it made no difference at all.

My car doesn't have the cruise control. Don't think that particular one came with it.