sand_man

All, I was recently noticing that in between up-shifts (clutch in) that the RPMs would sort of hang a little too high. I know this might be a good thing for a turbo car - keeping the turbo spooled and all that jazz, but it annoyed the crap out of me. It made it hard for me to match the revs when I released the clutch once my shift had been made. I prefer to be in control of this...not some valve! I also noticed that the idle was beginning to creep: yesterday with the car at operating temps, the idle climbed to 1300! So I did a little research on Pelican and found that the gold saucer looking thing located behind the ignition coil is the decel valve. My car is an '87. I pulled and plugged the hose on the front of it as well as the connection on the valve itself. Everything appears to be working fine now, and when the clutch goes in, the revs drop...just like I'm used to. I might go ahead and remove the thing all togther and plug the other two hoses on the rear of the valve. Here is the link to the info:
http://forums.pelicanparts.com/showt...r&pagenumber=2
Here is a pic...this is not the valve off of mine.

sand_man

In addition, one of the large hoses on the back of this valve is in very close proximety to the accelerator linkage and can be prone to rubbing...hence a vacuum leak could occur. Just food for thought if you are having problems with your idle and you have ruled out a faulty WUR, AAR, and/or AAV.

Jeff

A930Rocket

I ditched mine when I got rid of all the emmisions crap.

slownrusty

Read the Pelican thread with great interest...thanks for the link Sand_Man!

Yasin

NSXTC

I have the same problem where the rpm would hold and once the engine was warm, also idled around 1300-1500. Disconnecting the vacuum to the decel valve did the trick. Except now, I get really bad popping on decel, esp after WOT. A little annonying. So I guess the decel valve is the culprit. I may spring for a new one. Any other fixes besides a new decel valve?

nathanUK '81 930 G50

I am also interested in understanding this part, check out my post, I am waiting for Stpehen to reply about how it affects the cars handling too.

http://www.turbo911.com/showthread.php?p=1174#post1174

sand_man

While my engine is out, I went ahead and removed my decel valve all together. Before, I had just disconnected it, but now that I have easy access, I thought I'd ditch the clutter for good. Please refer to the attached picture. What is the best practice here - should I connect the two openings (circled in red) with a hose or cap them off...not connected.

Chet 930

Yup. Did the same long ago. Actually I used mine as a blow off valve until it started doing the annoying idle and rpm stuff between gear shift thing then I chucked it. It worked pretty good although it was never designed for that. Its true function is to let SOME air into the cylinders to help reduce them from loading up with fuel only whenever the throttle body is completely closed. You'll probably be able to throw out some bigger flames out of the exhaust now.

sand_man

Right...I'm just trying to figure out what to do now that the valve is missing. Can anyone advise: connect the two metal hoses with a short hose, or cap them off???

Chet 930

No..dont connect them. Otherwise the throttle body wont be able to control the air going into your manifold. Cap them off.

sand_man

Thanks, Chet!

Chet 930

A930Rocket

Heat the intake just enough to loosen the adhesive holding the fittings in, then tap them for a 1/2'' plug I think it is. Use lots of grease to keep the shaving from falling in. Then screw in your plug with Teflon tape to seal.

Sooner or later the cap/hose will rot or blow off when you don't want it to. AND it will be hard to plug it back up.

Chet 930

What I did on my other 930 after removing the aluminum tube from the manifold was I used a rubber expansion plug that had a nut at the end. As you tighten the nut, the plug expands and creates a very tight fit that doesnt come off unless you loosen the nut. Its the same item (but smaller) thats used on boats to drain out any water that seeps into the hull. I too had fabricated something the first time that came off right when I didnt need it to. The expansion plug never came off the 5 years I had the car.

sand_man

Thanks for great advice guys!