BAC??? whats the deal!??! help me real quick!
 

ok, so on cold start the engine requires me to give it throttle to keep it going some of the time, other times it goes through its cold start cycle just fine!!!

when i un-plug my BAC, i notice NO difference in idle. is this becuse the BAC is not working properly?

I did search but i need something specific! thanks! :scratch:

Check the thermowax on the back of the TB and the coolant lines going to it, i think theres probably a thread on adjusting/setting the TB and AWS.

When the car is warmed up, at the lights for example if you move the steering wheel does the idle change? I have a problem sometimes with my idle sticking at around 1000rpm after being reved then it will take some time to drop back down to 750rpm unless the PS/headlights/AC etc are activated

Just talking about the BAC........if the engine is fully hot, and you unplug the bac with NO change in idle speed, I'd suspect the BAC isn't working. UNLESS you have a idle speed well over 800rpm, then the above does not apply.

Just a simple test. Get the engine fully hot. Turn it off, then key ON. Go to the bac. You hear it vibrating or not? No? Then reach over and open the throttle more, and listen again. Key ON, engine off duing the above.

Or since the BAC is held with two nuts and a hose clamp, unbolt the BAC and rotate it where you see the internal diaphram. Have someone turn the key to START. The diaphram should go full open when the key is HELD to START. If you pull small wire off the starter solenoid prior to doing this, it will be easier to see the diaphram go full open as the key is HELD to START. Just lay on the ground near the left front tire. Reach over to the starter and by feel, find the small wire and pull it off.

I have the same problem with my BAC, pull the wire off and no change in idle. Except my idle is about 1500rpm's.

And for some reason it will NOT drop below that, i already checked/disabled the thermowax since mine was messed up but my idle is still 1500. I checked the BAC and it looks to be closed when no power is given to it. Where the extra air is coming from is beyond me.

The BAC will only effect idle below approx 750 rpm, so pulling the plug off at above that speed has no validity.

A stuck BAC MIGHT cause that high rpm even with the plug on or off. Only way to prove that is to pull the BAC and put a solid piece of gasket paper b/t the bac and intake then reinstall the BAC. Probably not your problem but possible.

Somehow you NEED to look in the throttle body at the throttle plates and make sure they are closed all the way (HOT ENGINE ONLY). Most likely SOMETHING is keeping the throttle plates open just a touch. A large vacuum leak AFTER the throttle body could cause the high rpm also. Like a vacuum line on wrong. I forget what car you have. Turbo/non turbo.

I have an 87 non-turbo, i need to add that tot he sig.

And i checked the TB plates the other day and found the thermowax to not be working right. I disabled it and still no change in idle, though it did seem smoother but still 1500 rpm. The plates are closed, i know that for a fact.

I have checked for vacume leaks many times, but i guess it can't hurt to try again. I heard somewhere that the vacume line roughting diagram is in the FSM, does anyone know where?

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Thanks, but that looks like a turbo diagram? or is the picture just not showing all the ports and the intake as it really is?

Turbo. Sorry 'bout that. I don't have a non turbo jpg like that.

Large nipple on the front of the dynamic chamber is to the oil injectors spider.

Middle nipple goes to the fuel injector air bleed nipple located b/t the two oil injectors on the lower intake manifold. You have to remove the dynamic chamber to see that nipple.

Bottom nipple has vacuum and goes to feed the lines on the solenoid rack on the left side of the engine.

There's a nipple on the left side of the dynamic chamber that goes........duh I forgot. I'll look sometime. To the vacuum lines on the solenoid rack. I forget.

The two lines on the back of the dynamic chamber go to the purge valve. One line on it's bottom and one line on the top of the purge valve..........but they route there thru the hard lines on the vacuum rack.

I might give a better answer later...maybe.

About that bank of solenoids, what ARE those?

I will go check the lines later, though that sounds about how i remember them.

The Blue, yellow, orange, grey solenoid (elect plugs) on the left side of the engine. Goes to the vacuum tubing for those solenoids. The jpg is not my car, someone elses on this forum.

If the two small hose were crossed, you could just try to swap them right now and see how it effects the idle. Easy to put back as it was.

Third jpg shows the fuel injector air bleed nipple. The middle nipple on the dynamic chamber feeds this nipple.

Oil injector spider is shown in the fourth jpg. IT's black with five nipples. It has one large nipple. The large nipple on the front of the dynamic chamber feeds this spider.