with nothing on my idle is fine, about 700 or 800 rpm but with the lights or ac on and the brake depressed the idle is kinda low and unstable close to 500 rpm and the lights dim, she stalled on me once while i had the ac lights and brake light on

how do i adjust this, or is there something i need to replace? S5 GXL

Thanks

 

Start with verifying the Throttle Position Sensor is within specs & voltage ranges. You can search for more details here "TPS adjust" or download the shop manual from www.teamfc3s.org

 

See if the bac is functioning or not. Its purpose in life is to bypass air around the throttle plates and help maintain an idle around 750.

Try warming the car up fully then turning the a/c on or whatever is dragging your idle down. Then as the idle sags down to that low figure......pull the bac's elec plug off. There should be a change in the idle when you do that and also a change when you put it back on the bac.

If there is no change whatsoever when removing or putting the bac plug back on......then suspect something is wrong with the bac or bac signal from the ECU.

No change at all????? Then pull the bac off. Put the elec plug on the bac. Turn the key to ON. Touch the bacs inner piston. It should be vibrating. PUll the throttle to full open and let go. The vibration should increase momentarily. If none of that happens......look for a pushed back socket in the bac's electrical plug. NO pushed back socket?? Suspect the transistor in the bac being shot. A new transistor cost about a buck fifty.

If the bac does vibrate, get some carb cleaner and spray the internals of the bac while its vibrating. Wash it out with the fluid and repeat several times. Reinstll it and see if things got better.

If you look at your FSM's chart dealing with bypass air control, on a series five it shows several things that if engaged will cause the bac to react and increase the air bypass to the bac. One of which is the a/c and another the lights. A series four will also react to the headlights or the brake lights, even though the chart does not indicate that the bac is effected by lighting.

Done.

 

^^ you're up early this morning

 

Thanks for the help guys. I'll check the TPS and BAC today.