Parts Catalog Accessories Catalog Tech Info Tech Forums
 
  Search our site:    
 Cart  | Project List | Order Status | Help    
Go Back   Pelican Parts Technical BBS > 1- Porsche Technical Forums > Porsche 928 Technical Forum

Reply
 
LinkBack Thread Tools Rate Thread
Author
Thread Post New Thread    Reply
1979 5sp 928 project
 
Join Date: Apr 2012
Location: Boise Idaho
Posts: 184
Garage
shark revs too high until i bump it down...any suggestions?

The 79 is running great but I have one problem (actually many, but one for this post). My shark idles at about 1000 rpm, but when I come to a stop it will idle at about 1500 to 2000 rpm until I rev it up quickly and then it will drop down to (normal) idle. I realize I should be about 800 rpm, but she really likes 1000. I just need help determining why it's not returning to idle on her own without being reved first. One rev up to about 3000 will bring it back down to 1000, but if I just push in the clutch and come to a stop, it's stuck between 1500 and 2000.

Any ideas?

Thanks in advance for your help.
__________________
1979 928 5sp project
1984 928S 5sp black on black
Old 07-18-2012, 10:34 PM
  Recommend this thread for the PelicanWiki    Reply With Quote #1 (permalink)
Network Native
 
Danglerb's Avatar
 
Join Date: Jan 2007
Location: SoCal
Posts: 9,536
Throttle linkage sticking?

I don't think the 79 has any special active idle control, maybe a vacuum limiter?
Old 07-19-2012, 12:31 AM
  Recommend this thread for the PelicanWiki    Reply With Quote #2 (permalink)
Kool
 
AirtekHVAC's Avatar
 
Join Date: Mar 2012
Location: China Grove, NC
Posts: 1,568
Garage
perhaps a gummed up butterfly under the spider...mine was gooped shut...

(Why are we talking bugs here?)
__________________
--------------------------------------
Ron
1978 5sp (#30) project-Wreckscue
Old 07-19-2012, 01:12 PM
  Recommend this thread for the PelicanWiki    Reply With Quote #3 (permalink)
Registered User
 
Join Date: Oct 2005
Location: Owasso, OK
Posts: 386
Garage
Make sure there is some slack in the throttle cable. If too tight at idle it can be adjusted at the firewall. Also, the cruise control cable can become sticky and cause this problem, especially if you don't use it. BTDT
__________________
Dennis
Old 07-20-2012, 05:38 AM
  Recommend this thread for the PelicanWiki    Reply With Quote #4 (permalink)
Registered User
 
Brenton928S's Avatar
 
Join Date: Mar 2010
Location: South Australia
Posts: 49
Garage
I had the same problem on my '82 S and i found it to be the throttle linkage at the throttle body going over centre and holding the throttle open a bit more than it should be. A simple adjustment of the linkage cured it and all is good now. Idle RPM should be at around 1000rpm.
__________________
1982 928S M28.11 Auto
Old 07-21-2012, 04:16 PM
  Recommend this thread for the PelicanWiki    Reply With Quote #5 (permalink)
Registered User
 
JK McDonald's Avatar
 
Join Date: Oct 2003
Location: Texas
Posts: 561
Garage
Auxillary Air Device - Adjustment

Hey Boise Shark, On some of the early CIS cars there was an auxiliary air device that can cause a hang up or failure of the throttle to return to the preset idle. The aux-air device is usually mounted very close to the air flow meter/throttle assembly. The symptom that I’ve seen is that you can blip your accelerator and the idle will often fall back to the correct point. One other quirky symptom is that if you “lug” the engine down using 1st gear, the vacuum signal inside the aux-air device is sufficient to overcome it's internal spring tension and force the idle back down as well.

If you have this aux-air device, it will be a fist size bell shaped looking gizmo with a 5/8” air hose connected to one end and another 5/8” hose connected to it's side. There is also a small 1 /4” hose that plugs in over a small vacuum orifice within a snout. The snout has two flat sides (under the 1 /4" air hose) for making adjustments. If the aux-air device is out of adjustment - simply remove the small hose, loosen the lock nut at the base of the snout and turn the snout a couple of turns in. I use a small crescent wrench for setting the internal spring tension. Snug down the lock nut, reconnect the small air hose and take’er for a run.

Perhaps someone with a CIS vehicle could add a photo of this aux-air device. I do not currently have anything with this component installed.

Good Luck, Michael
__________________
Frauhelga - 1987 Porsche 911SC
Beuford - 1995 Porsche 968
Miss Purdy - 1984 Porsche 928S
Lady in Red - 1985 Porsche 928S
Billy Bob - 2002 Porsche Boxster Spyder
Old 07-21-2012, 07:57 PM
  Recommend this thread for the PelicanWiki    Reply With Quote #6 (permalink)
 
Now Available for Ordering:   101 Projects For Your BMW 3 Series 1982-2000  [more info]
928 Newbie
 
dcrasta's Avatar
 
Join Date: Feb 2010
Posts: 451
Garage
Get some carb cleaner and some gum cutter. Spray the bejesus out of your linkages , aux air control device, butterfly, etc.

Follow up with some wd -40 (carb cleaner leaves things unlubricated). This would be a good time to lube the throttle cables.


Return with results.
Old 07-22-2012, 07:41 AM
  Recommend this thread for the PelicanWiki    Reply With Quote #7 (permalink)
1979 5sp 928 project
 
Join Date: Apr 2012
Location: Boise Idaho
Posts: 184
Garage
Haven't been on in about a week. Thanks for all the suggestions. I'll put them all to work and see if I can't get a cure and will let you all know how it comes out.

JK, I think I know what your are talking about. The 5/8 airhoses go directly into the air intake on the lower plenum (the four inch round chamber that hits the bottom of the spider)
__________________
1979 928 5sp project
1984 928S 5sp black on black
Old 07-22-2012, 08:30 AM
  Recommend this thread for the PelicanWiki    Reply With Quote #8 (permalink)
Old 07-22-2012, 08:30 AM
Reply

Thread Tools
Rate This Thread
Rate This Thread:

 



All times are GMT -8. The time now is 09:27 PM.


 
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2011 Pelican Parts - Posts may be archived for display on the Pelican Parts Website -    DMCA Registered Agent Contact Page
 

DTO Garage Plus vBulletin Plugins by Drive Thru Online, Inc.