2nd Generation Specific (1986-1992) 1986-1992 Discussion including performance modifications and technical support sections.
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starts but no idle

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Old 02-20-15, 11:00 PM
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Excuse my ignorance, how can a lack of a BAC cause it to run rich? Any air bypassed by the BAC will be read by the AFM. So more air, more fuel.. No?

Running rich, to me, would indicate either blocked fuel return, jammed shut FPR, coolant temp sensor out of range, a bad AFM, or leaky injectors... A bad O2 sensor will also cause a rich idle.
Old 02-20-15, 11:41 PM
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So I don't need a bac is that wat ur telling me
Old 02-21-15, 10:32 AM
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Originally Posted by 87nitefc
So I don't need a bac is that wat ur telling me
You have a turbo. If you had an NA then the idle adjust screw would be located on top of the engine. On a turbo there is no screw on the top of the engine. On the turbo the adjust screw is located at the BAC. If you don't want an air adjust screw then don't install a BAC. The BAC is used to help maintain a proper idle and it's there for a purpose so without the BAC you lose the air adjust screw and a method for maintaining a proper idle.
Old 02-21-15, 10:48 AM
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Is it possible to interchange Tb from Na to turbo just for the adjustment screw
Old 02-21-15, 10:53 AM
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dude, STOP, ill sell you my BAC...
or buy one of these http://www.ebay.com/sch/i.html?_odkw...valve&_sacat=0
Old 02-21-15, 11:59 AM
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Yeah, get a BAC if you don't have one.

I just wasn't sure how a lack of one could make it run rich.. Just poor or no idle..
Old 02-21-15, 12:04 PM
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Are you sure it has a standard ecu?

Often the BAC is left off when changing to a Microtech or other basic aftermarket computers.
Old 02-21-15, 05:21 PM
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Yeah stock ecu currently
Old 02-21-15, 05:50 PM
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You also have the variable resistor to help adjust the fuel mixture for idling only. The engine should be completely warmed up before making this adjustment. The adjustment screw is located near the boost sensor on a diamond shaped piece of metal.
Old 02-21-15, 08:30 PM
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Originally Posted by satch
You also have the variable resistor to help adjust the fuel mixture for idling only. The engine should be completely warmed up before making this adjustment. The adjustment screw is located near the boost sensor on a diamond shaped piece of metal.
This should help me lean my engine out
Old 02-21-15, 09:20 PM
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Originally Posted by 87nitefc
This should help me lean my engine out
To a small degree. Usually the resistor is set to more rich than lean. The screw does not rotate too much. Pretty much from 8:00 o'clock to 4:00 o'clock. If you try to turn it pass these resistance points you'll break it.

Last edited by satch; 02-21-15 at 09:24 PM.
Old 03-01-15, 01:38 AM
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So today I took my car to work seemed good I had a jumpy 1,500 rpm then when I had gotten out she starts but is idleing low compared to before now she was at 650 I gave a Lil gas and she died out I did notice my volt gauge is going nuts really unsteady I also notice my right signal light on my dash flickers for a few sec I'm not sure how good is this info but I'm guessing there has to be a short somewhere based on how my gauge is acting up I'm also getting huge amount of smoke any input about this
Old 03-01-15, 11:49 AM
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The output wire of the alternator should read 14 volts while idling/driving (belt might be slipping).

As stated before, the BAC helps to keep a steady idle at 750 rpm and prevents the idle from dropping down below 750!!!!!!!!!!!!!!!!!!
Old 03-01-15, 12:04 PM
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OK I got a bac where can I find a hose diagram for it.
Im planning to install a safc or AFC neo does it help with tuning
Old 03-01-15, 12:48 PM
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Originally Posted by 87nitefc
OK I got a bac where can I find a hose diagram for it.
Im planning to install a safc or AFC neo does it help with tuning

The service manual. And if you have a stock setup I'm not sure aftermarket devices are of much help but I could be mistaken.
Old 03-01-15, 12:48 PM
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So this is where I'm at belt was a Lil loose so this is after I had tighten the belts

Old 03-01-15, 01:23 PM
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Again, the BAC is there to help the idle from dropping below 750 rpm. Did you measure the output of the alternator or not. If you did what was it? If the voltage drops so will the engine speed.
Old 03-06-15, 02:23 PM
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Based on the pic of the bac on which side does the b/w wire connect to

starts but no idle-forumrunner_20150306_122153.jpg

Got it its the L/G_B/W
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