Failed BOV?
 

Car idled at 1900 rpm since the day I bought it back in May. I've put about 500 miles on it since then.

Finally got around to messing with it. It has an ARC blowoff valve installed, venting to ATM.

I started adjusting the screw on the top, and as I turned counter-clockwise, idle started to drop to closer to where it should be. I took the screw ALL the way out, and now it idles at 1100 rpm. I also never realized I was never getting the characteristic pshhhhhh sound that I should have been getting.

Its got the stock turbo... I'm still learning about these hairdryer looking things, so take it easy on me!

And after doing some reading, I found out that the sound I was getting prior to removing the screw was flutter. Now the flutter is essentially gone, and I'm getting the typical pshhh sound, though it doesn't seem as sharp as I thought it would.

eh, after staring at random BOV internal diagrams, if looks like there was some kind of leak in the upper chamber where the vacuum hose hooks up... I'll tear it apart when I get home.

Also remember the volume of the noise is proportional to the cfm and psi escaping. So a stock turbo at 8psi is not as loud as a T4 at 8psi or a T88 at 2psi.
Hopefully that makes sense

Whats up Rob? Welcome to turbocahargers, your life will never be the same.... Be sure to check for any un-metered air and any vac leaks throughout the system, that will put a damper on the pshhhh sound and make the idle high as well.

i was surprised that I was able to bring the idle down that quickly... another few hundred rpm's and i'll be set!

plan for now is to get a turbonetics BOV (new) off of craigslist that I just found. gotta weld up the bung onto a steel pipe though... i'm not so hot on the epxoy idea. he also has a fmic... both of these for 100 bucks. not sure on the FMIC brand. what do you guys think? link is below:

http://gainesville.craigslist.org/pts/1944580063.html

oh SNAP... albert, whats going on?


i drove up to richmond on my birthday for this new money pit. 8400... suspension was trash, tires were trash (2 still are). but it's got a jspec tII, body kit, and some good looking paint on it! it drives straight (now).

just need a set of springs (i replaced all 4 shocks/struts with AGX's... and the ball joints), 2 more tires, and a new exhaust... i'll be good to go!

for those who are wondering what i'm working with... the picture is attached!

I'd like to start this whole thing over again... as I went and did some tinkering earlier, and maybe can describe my issue a little better.

1) 88 Vert body
2) 91 JSpec 13bt
3) ARC blow off valve

When I purchased the car, the car idled (and effectively, still does) at a solid 1900 rpms. 5 months later, here I am... finally ready to start learning something about turbos. Here's what I've figured out so far...

1) when I removed the spring adjusting screw altogether from the BOV, my idle drops to a good 1100 rpm.
2) when configured like this, the car will not idle until warm.
3) vacuum is evident from the OUTPUT of the BOV with the screw removed.
4) when the screw is installed, the vacuum leak at the output ceases.
5) when the screw is installed, and I remove the vacuum line from the BOV, idle speed increases...

So how is it that #5's vacuum leak increases idle speed, and #3's vacuum leak decreases idle speed... I dont get it. Both are post - MAF sensor...

I'm not sure, but I believe you can thank the BAC for that one. Unplug the BAC and see if that helps at all with your high idle.

you can try spraying around the bov with carb cleaner. If the idle changes, there is something wrong with the BOV since its leaking air.

You tried looking at the Throttle body and checking to make sure that the throttle plates are closed at idle? IF it is then you can check the back side look to see if the dashpot is stuck open. Check the fast idle linkage.

You can try taking the blow off valve out and plugging the hole and running the car at idle to see the rpm. If it returns to normal or the rpm drops then the BOV is bad or set wrong

Unplugged the BAC... no change at all. What I did notice though was that it doesn't have the N370 tag on it like the ECU and MAP etc sensors do though... is that an issue? It has another number on it (cant remember it right now).

I'm leaning towards a bad BOV, but who really knows. I'll pull it off and start plugging holes tonight if I get a free minute.

You say it has a JDM swap? Does it have the JDM ecu as well? USDM S5 T2 ecu numbers are N370 and JDM S5 T2 is N374. There's usually no problem when running 370/374 sensors/ecu in conjunction, but I know there are some exceptions.

Not even sure if that has anything to do with it, just thought I'd point it out as it could.

it sounds like a bad BOV. i had a similar issue with a greddy one i had. but when you said you pulled the vac line off and idle increased it makes me think you have another vacuum leak somewhere.

its a good idea to check all your vac lines every once in a while anyway. with all the heat the turbo model puts out those lines can crack very easily or split and you could never know it. carb cleaner will be your best friend for vac lines.

Yes, the ECU is n370, and the BAC is n374... so I guess that eliminates that possibility.

I'll pull the intercooler off and start replacing random vac lines tomorrow I guess... A new BOV wouldn't hurt either, this one looks like its been around the block a few times.

I suppose I was reluctant to suspect it since it was an ARC one. I really dont know how old it is... but again, it looks far from new. Anyone have one laying around for sale? (I'll check the FS section in a little bit.)

Any restrictions on which one I can run? Its just the factory turbo, I suppose it doesn't REALLY have to have one, but I've read that flutter isn't such a good thing.

ive got a blitz knockoff that would need a flange ill sell ya dirt cheap (its the oval 2 bolt flange, may be the same as the arc)