Need opinion: BAC Valve off spec by 1.6 ohm
08-29-09, 08:05 PM
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Need opinion: BAC Valve off spec by 1.6 ohm
So I thought the loosen clutch switch was causing the low idle rpm on my 91 S5 N/A, but turns out that is not the case. I then checked the next candidate, the BAC valve. Now the FSM says that the permissible resistance is 10.7-12.3 ohm (F1-41), mine was 13.9 ohm. I also tried connecting a 12v power source and the valve does click.
I am looking for advise--should I replace the BAC value base on its current condition?
I am looking for advise--should I replace the BAC value base on its current condition?
08-30-09, 06:39 AM
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Probably not.
Try this: Remove the BAC but leave the plug on. Stare at the guts of the thing. Have someone turn the key to Start. When the key is HELD to START, the BAC'S piston should move and stay open. Key word...HELD to start. I think that would prove the ECU is talking to the BAC. If the BAC does not move when the key is to Start, then there is probably a ECU problem OR, OR one of the two wires in the PLUG for the BAC is pushed back in the plug and not making contact with the BAC's jack.
You might remove the small trigger wire off the starter motor when doing the above. Helps, but not required. But you really don't want the motor turning over 'cause with the BAC off, the engine isn't going to start anyway (probably too much air).
Or remove the BAC but leave the connector on it. Block off the BAC hole in the manifold with something and start the engine. Watch the guts of the BAC vibrate. Should be vibrating at approx 120hz or so.
Never ever pry on the guts of the BAC with anything.
IF the key is ON and the BAC is vibrating, it's working. Get the engine hot then key ON, engine Off. Listen at the BAC for a buzzing from it. No buzzz? Then reach over there and open the throttle a bit and see if it starts buzzing or not. Maybe ***** the wire with a sewing needle and put the meter lead to the needle? Neg lead to any good gnd nearby.
IF you had a meter with the FREQ feature, you could tap into the wire b/t the ECU and BAC and watch the frequency to determine if it was working or not. You'd see around 120hz when working.
OR if a meter is put on the wire b/t the BAC and the ECU, you'd see the voltage vary when a load was put on the engine. Like turning the A/C on or headlights or?? The wire b/t the ECU and BAC is the wire on the BAC plug that IS NOT black/white. Plug has to be on the BAC when doing that. It's been a while since I've done that. I vaguely remember something like 9vdc when operating. I might check that later with a hot engine.
Try this: Remove the BAC but leave the plug on. Stare at the guts of the thing. Have someone turn the key to Start. When the key is HELD to START, the BAC'S piston should move and stay open. Key word...HELD to start. I think that would prove the ECU is talking to the BAC. If the BAC does not move when the key is to Start, then there is probably a ECU problem OR, OR one of the two wires in the PLUG for the BAC is pushed back in the plug and not making contact with the BAC's jack.
You might remove the small trigger wire off the starter motor when doing the above. Helps, but not required. But you really don't want the motor turning over 'cause with the BAC off, the engine isn't going to start anyway (probably too much air).
Or remove the BAC but leave the connector on it. Block off the BAC hole in the manifold with something and start the engine. Watch the guts of the BAC vibrate. Should be vibrating at approx 120hz or so.
Never ever pry on the guts of the BAC with anything.
IF the key is ON and the BAC is vibrating, it's working. Get the engine hot then key ON, engine Off. Listen at the BAC for a buzzing from it. No buzzz? Then reach over there and open the throttle a bit and see if it starts buzzing or not. Maybe ***** the wire with a sewing needle and put the meter lead to the needle? Neg lead to any good gnd nearby.
IF you had a meter with the FREQ feature, you could tap into the wire b/t the ECU and BAC and watch the frequency to determine if it was working or not. You'd see around 120hz when working.
OR if a meter is put on the wire b/t the BAC and the ECU, you'd see the voltage vary when a load was put on the engine. Like turning the A/C on or headlights or?? The wire b/t the ECU and BAC is the wire on the BAC plug that IS NOT black/white. Plug has to be on the BAC when doing that. It's been a while since I've done that. I vaguely remember something like 9vdc when operating. I might check that later with a hot engine.
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alexdimen
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