adjusted my tps to 1k ohms at rest and 4.6k ohms WOT.. still having idle issues
08-25-12, 06:08 PM
#26
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Diagnosing idle really isn't all that complicated.
If you disconnect your BAC at idle with no load and the idle drops significantly, your mechanical idle is set too low or you have a further problem. Disconnecting the BAC at idle should result in little or no change at all. From what you've said, it sounds like the BAC is having to compensate too much just to keep your idle normal with no load, so any load at all is taxing it beyond its ability.
The BAC is just a valve that allows air to bypass the throttle plates, it can only bypass a certain volume of air. So, say this valve is working at 60% just to keep your car idling normally, and you press the brake or turn the light on and it suddenly goes to 100% and can barely keep up with one, let alone both? The idle suffers because it can't pass enough air to keep it going. The point is, the duty cycle should be VERY low at idle, so the valve has the maximum available duty cycle to compensate for varying loads to keep the idle normal.
In any event, if the idle is low with the BAC disconnected, TPS adjusted properly, and timing is correct then you need to adjust the mechanical idle up. Get it to around 700-750, then adjust TPS, reconnect BAC and all should be well in the world.
This is of course assuming you don't have massive vacuum leaks (usually van leaks cause the idle to 'float' high, but a LARGE leak can cause it to be low).
If you disconnect your BAC at idle with no load and the idle drops significantly, your mechanical idle is set too low or you have a further problem. Disconnecting the BAC at idle should result in little or no change at all. From what you've said, it sounds like the BAC is having to compensate too much just to keep your idle normal with no load, so any load at all is taxing it beyond its ability.
The BAC is just a valve that allows air to bypass the throttle plates, it can only bypass a certain volume of air. So, say this valve is working at 60% just to keep your car idling normally, and you press the brake or turn the light on and it suddenly goes to 100% and can barely keep up with one, let alone both? The idle suffers because it can't pass enough air to keep it going. The point is, the duty cycle should be VERY low at idle, so the valve has the maximum available duty cycle to compensate for varying loads to keep the idle normal.
In any event, if the idle is low with the BAC disconnected, TPS adjusted properly, and timing is correct then you need to adjust the mechanical idle up. Get it to around 700-750, then adjust TPS, reconnect BAC and all should be well in the world.
This is of course assuming you don't have massive vacuum leaks (usually van leaks cause the idle to 'float' high, but a LARGE leak can cause it to be low).
08-26-12, 12:21 PM
#27
it also closes fully when you are off idle, which is what causes it to always want to stall out when you let off the throttle. there is no idle learn KAM in these ECUs so setting the idle and making sure there is no vacuum leaks is very important.
if you have the idle adjust air bleed screw all the way out and it still isn't enough you likely have significant vacuum leaks, timing is retarded or TPS out of adjustment. if the idle screw is in all the way and idle is too high then something is mechanically holding the throttle open, ie stuck thermowax or throttle cable too tight.
if you have the idle adjust air bleed screw all the way out and it still isn't enough you likely have significant vacuum leaks, timing is retarded or TPS out of adjustment. if the idle screw is in all the way and idle is too high then something is mechanically holding the throttle open, ie stuck thermowax or throttle cable too tight.
Last edited by RotaryEvolution; 08-26-12 at 12:24 PM.
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