2nd Generation Specific (1986-1992) 1986-1992 Discussion including performance modifications and technical support sections.
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Old 06-10-08, 07:21 PM
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bov questions

can anyone tell me if the bov is supposed to close all the way or not? Its and 87 gxl with full t2 conversion, staight pipe from turbo to factory n/a catback, fcd, and home made intake. its not idleing very well, misses a lil bit at idle, when unplug the bov from the intake to make it atmospheric and plug off the intake the car wont idle at all unless i plug the end of the bov and then it clears right up and dont miss at all. i guess what im asking is, is my bov not functioning properly or is it supposed to leak air all the time???
Old 06-10-08, 07:51 PM
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The whole point of the BOV is to vent off pressurized air when you let off the gas. Aftermarket BOVs vent to atmosphere, so your stock one should be able to as well. What kind of boost are you able to reach with it constantly venting? It should be closed fully.
Old 06-10-08, 07:55 PM
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The valve is supposed to be closed at all times except when you let off the gas after boosting. When you let off the gas the intake after the throttle body becomes a large vacume instantly which in combination w/ the pressure built up by the turbo before the the throttle body pushes the spring in the valve to open. After pressure's balance it closes again. You probably have a bad or improperly installed valve. i doubt its installed wrong though but check where your getting your vacume from. I just helped my dad diagnose a Saab turbo that was doing the same thing. The customer was complaining about an odd sound which was the compressor surge from a non functioning valve.
Old 06-10-08, 07:56 PM
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i get to around 9 psi at full throttle, and if its supposed to close fully then i guess i need a new one, is it cheaper to go aftermarket?
Old 06-10-08, 08:03 PM
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No, it's cheaper to get a used one from a forum member. Cheapy ebay ones are around $30-50, and name brand aftermarket BOVs are $100+.
Old 06-10-08, 08:09 PM
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Get a nice aftermarket one it will make you smile lol.
Old 06-11-08, 12:43 AM
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yeah i think ill just go aftermarket, any suggestions???
Old 06-11-08, 01:54 AM
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Don't buy an aftermarket one.
Don't buy a used one.

Your BOV works just fine. Plug it in. The stock BOV is open at idle. If you unplug it, you now have a vacuum leak.
Old 06-11-08, 02:24 AM
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really??????
Old 06-11-08, 11:39 AM
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Yes, so when you vent it to atmosphere, at idle it is open allowing a decent size vacuum leak.

You probably have something else going on, like another vacuum leak, TPS out of adjustment, or in need of a simple tune up. The FAQ should contain help in figuring out idle issues.
Old 06-11-08, 02:41 PM
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True- the stock BOV is open at idle to bypass the turbo. If you want to opt for an aftermarket BOV, look into Synapse Engineering. They offer a top of the line BOV that is designed to function first and foremost. Try to avoid the cheaper BOV's as quality may not be as good.
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