the idle on my rex was over 1000 rpm, like 1100 or 1200, so I adjusted it to below 1000 (750 I think). When I turn on the air it goes down to about 300 or 400 RPMs, and when I turn the AC on when the car is real hot, it dies off? But when the car is cold it doesn't die off, since the RPM's are high. anyone know what this is? I'm thinking some kinda vacuum leak. LMK, thx

 

im no expert with idle but it sounds like the BAC valve is not working. its on the side of the throttle body, sorta little cylinder thing with an electircal plug, 2 big air hoses and 2 small coolant hoses connected.

if you run the car at normal idle temp, and unplug the electrical plug from the BAC valve, the idle should drop slightly.

theres plenty of info on the bac and idle probs if you search

 

yeah my car does the same exact thing...... i turn on the a/c and it idles like **** bouncing from 200-900 rpm... and it dies off sometimes.... dont worry... we all have problems jajajaj mines idles like urs too.. i think i have a vacuum leak as well... and i was questioning the bac too

 

Jumper your initial set coupler and check out the idle. Should be able to set it at 750. If you can't then you need to find out why you have the high rpm's. Pull the plug off the bac while there to make double sure that its not interfering(superfluous, I know). If you have it set at 750 and then take the initial set coupler off, and then turn the a/c on and the rpm drop to 300 whatever, then you need to investigate whether or not the bac is getting a signal from the ECU. Car wasn't meant to act like yours does.

 

i am having a similar problem hailers. i would like to use your advice to check it out, but i need to know what and where the initial set coupler is. thanks man.

 

Here we go.....I am having this problem too. Mine started when I removed all my emissions and valves on the intake (didn't remove the BAC). I have been told by several people that the BAC does not compensate for the AC, only other engine loads (that's contrary to what I had heard in the past). Anyway...could it be one of the other valves on the intake (Air Supply Valve???) that compensates for the AC????

My car is an '87 TII and the idle went up a little with the AC turned on until I removed all the extra valves and blocked off the holes.

Todd

 

The BAC compensates for the load of the A/C. I have monitored it with a meter. When the a/c is turned on you see a voltage drop on the power to the BAC of two to three volts when at idle.
On a 87-88 model the initial set coupler is near the lead coils. Green in color, two socket. You jumper the sockets with a piece of wire. I understand the 89 and on have a single green connector near the lead coils, that you jumper to ground.
The www.fc3s.org is supposed to have a(EDIT) 90 factory manual on line since sometime last week, and if you download the FUEL section it should, just like the 88 manual, have a section setting the idle by jumpering the initial set coupler.
P.S The air supply valve on the back of intake on a TurboII, has its plug disconnected on my car. Its used just for power steering and hot starting. If you have power steering on a turboii, and turn the wheel, the air supply valve opens and compenstates for the load. The AIR BYPASS SOLENOID VALVE on a turboii located just aft and inboard of the BAC on a turboii, is used for the 17 second, 3000 rpm (approx) start up of the car when the temp of the car is cold.
If I thought that my BAC was suspect, I'd cram a meter lead in the back of the BAC and monitor the voltage of the BAC with the A/C off and then on. Should see a voltage drop of a couple of volts. If the the BAC is not working I'd go to http://www.teamfc3s.org/info/articles/idle.html and look at the troubleshooting of the BAC at the bottom of this article, whether or not I had a turbo or na. I had a bad transistor in a spare N332, turbo ECU and replaced it to these instructions. It works now. Part from RadioShack, a soldering wick for a buck, and truly minimal soldering skills.

 

HEY ROTORHEAD! Look at this site and the 89-91. It has a picture of the initial set coupler on your car http://home.rmci.net/panther/89_91ecu.htm
REXRYDER: If your car idles at 750 approx, and the car is warmed up, go to your BAC and pull the plug off. There should be a slight drop in the idle speed. If there is no reaction at all, you NEED to go to the article mentioned in the post before this one and check out the signal from the ECU to the BAC. Not difficult. There is a possibility the transistor in the ECU is fried, but is easily repaired.