[RESOLVED] throttle body screw leaking air!!!

[vince_w2004]

I did a boost leak test again over the weekend and found a small stream of air leaking from the screw on the top of the throttle body. When i tightened it went away of course but my real question is what is this screw for and does it effect anything when you turn it?

 

[xveganxcowboyx]

Yes, it will effect your car when you turn it. That screw (called the BISS screw) is used to adjust the cars idle (see VFAQ.com for proper adjustment procedures).

There should be a plastic cap over the screw which you can get from the dealer, though I've never found it particularly important. What is probably leaking is the O-ring at the bottom of the screw. You'll have to unscrew it as far as you can and then possibly pressurize your system with a couple pounds (don't go nuts or you'll shoot the thing across the room!). You can get a replacement O-ring from the dealer or find a matching one at the hardware store. If you search you'll probably find the exact specs for a hardware store equivalent.

This may be a good time to remove the whole throttle body and replace it's seals and gaskets as well as give it a thorough cleaning.

 

[lilbro717]

i would just go to a junkyard and get a new TB

 

[snowborder714]

^ You don't need a new throttle body. You just need to replace (at minimum) the o-ring. But to be safe, you could get all 3 parts.

BISS Screw Cap
Part number - MD614532
Price - $4.33

BISS Screw
Part number - MD614948
Price - $1.20

BISS O-ring
Part number - MD608806
Price - $2.86

OEM Mitsubishi Parts

Or for just the O-ring it's a #5 o-ring at your local hardware store.

Here's how to adjust the BISS:
http://www.vfaq.com/mods/BISS-1G.html

 

[kenamond]

#5 o-ring from your local hardware store...maybe 20 cents. It's a bit cheaper than a new TB...and a lot easier to install.

EDIT: doh! Didn't see that snowboarder said that.

 

[vince_w2004]

thanx guys fixed it!!!

 

[uberchargedDSM]

I'm actually taking off my tb and sending it off to get bored and rebuilt my shaft seals are shot. Another annoying thing to fix on my car. I'll be sending it off to this guy I've heard a lot of good feedback from him plus he's retired AF so maybe he'll give me a military discount haha.
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