Pelican Parts
Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help



Go Back   Pelican Parts Forums > Porsche Forums > 911 / 930 Turbo & Super Charging Forum


Reply
 
LinkBack Thread Tools Rate Thread
Author
Thread Post New Thread    Reply
Registered User
 
Join Date: Jul 2004
Location: Berkley, MI
Posts: 261
Garage
New 77 engine rebuild question

I just got my 77 turbo engine back from being rebuilt and installed into the original car. Engine was completely apart when I bought the car. It has been rebuilt pretty much to stock, except for new stainless headers and heat exchangers. Everything was checked, and the distributor, WUR, Fuel distributor were rebuilt.

I have driven it about 4-500 miles. There are a couple of issues that I am seeing when the car warms up:

- Hunting idle - When the car is cold, the idle is very consistent, about 1000 RPM, dependent on where the manual throttle is set. When the car has warmed up though, the idle hunts up and down. I looked at other threads for related issues, and it sounded like the CIS might be a little rich at idle. It all the other inquiries were for '78 or later. Would this be the same issue for the '77?

- Stalling at light - After the car is warm, when I decelerate coming to a light, the engine will consistently stall when i get to the light to stop, unless I blip the throttle, and then it will idle. It will not be a consistent idle, it will hunt as mentioned above.

- Major hesitation - I was driving the car this weekend for the last time this season. I was driving on th highway with moderate acceleration at about 75 in third. I had a hesitation that felt like it lost power and came right back. Don't know how else to explain it.

Any thoughts or ideas on the items above would be greatly appreciated.

Karsten

Last edited by kolies; 11-30-2009 at 04:18 AM.. Reason: Change title
Old 11-29-2009, 05:45 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #1 (permalink)
Registered User
 
Join Date: Jul 2006
Location: S. Florida
Posts: 7,274
The idle symtoms are those of it running too rich. Thats is usually easy to get pretty good by ear if the WUR and fuel head are in good condition and your fuel filter is clean.

The cutting out like you described sounds like one of the 3 relays in the fuel pump circut. There's 2 pretty reliable red ones in front - one for each fuel pump and a yellow one from hell in the back... could also be a loose wire on your ignition coil, or the plug in the bottom of the CDI is loose.
So many things in the car that could do that and the last ones on the list would be the ignition switch or possibly even the alarm system having fits.
Old 11-29-2009, 06:14 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #2 (permalink)
Registered User
 
Join Date: Jul 2004
Location: Berkley, MI
Posts: 261
Garage
I'll adjust the mixture according to the other postings I found. All three should be really good condition. The WUR and fuel head were both rebuilt with the engine rebuild, and the filter was also replaced.

I'll take a look at the yellow relay in the back. Could it be the CDI unit? Or is that one of these either it works or doesn't work part?
Old 11-29-2009, 06:23 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #3 (permalink)
Registered User
 
9dreizig's Avatar
 
Join Date: Jul 2005
Location: Reno NV, Bay Area during most weeks,, Kids still in NH
Posts: 5,781
Send a message via AIM to 9dreizig
My guess is that once you get the hunting fixed your stalling problem will go away as well. Only chase one problem at once!! If you plan on working on your car at all get a good AFR meter ( LM-2 or other)..
__________________
"Todd"
98 Tahoe ,2007 Saturn Vue
86 930 black and stock, 80 930 blue tracdog
91 Spec Miata (yeah I race a chick car)
"life"ll kill ya" Warren Zevon
Old 11-29-2009, 06:35 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #4 (permalink)
OFF THE BOOST PIPE NOW...
 
A930Rocket's Avatar
 
Join Date: Oct 2003
Location: Mount Pleasant, South Carolina
Posts: 7,413
Good advice above.

If he pulls the blue plug off the metering plate, would he need to jump the relays up front to rule out some fuel issues? I ditched all that stuff so long ago, I can't remember.
Old 11-29-2009, 06:41 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #5 (permalink)
Registered User
 
Join Date: Jul 2006
Location: S. Florida
Posts: 7,274
If everything is working right pulling the metering plate plug with the ignition on should turn on the fuel pumps.
With an intermittant problem it's impossible to trace while it's working right. All you can do is replace relays and clean switch contacts and hope it goes away.

If the factory alarm causes it then thats another uncomfortable adventure under the cowl windsheild area near the glovebox I havn't gotten into yet.
Old 11-29-2009, 06:59 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #6 (permalink)
 
Registered User
 
9dreizig's Avatar
 
Join Date: Jul 2005
Location: Reno NV, Bay Area during most weeks,, Kids still in NH
Posts: 5,781
Send a message via AIM to 9dreizig
two more of my cents.. If it's hunting at idle, and you come off a high rpm , foot off the accelerator clutch in,, it just drops out,, because it hit's "hunt mode" so hard from the high rpm it can't recover (don't ask me how I know)
__________________
"Todd"
98 Tahoe ,2007 Saturn Vue
86 930 black and stock, 80 930 blue tracdog
91 Spec Miata (yeah I race a chick car)
"life"ll kill ya" Warren Zevon
Old 11-29-2009, 07:22 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #7 (permalink)
Registered User
 
Join Date: Jul 2004
Location: Berkley, MI
Posts: 261
Garage
Did you get it to recover? Any adjustment that can be made?
Old 11-30-2009, 02:35 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #8 (permalink)
Registered User
 
Join Date: Jul 2006
Location: S. Florida
Posts: 7,274
Try leaning your idle mixture.
Turn the 3mm allen head CO adjustment screw counterclockwise or left for lean just a little bit to lean it out. You have to push the allen head down into the spring loaded CO adjustment thing next to the fuel head until you feel it engage and then you can turn it, but only turn it a little, the idle AFR changes quickly with small turns of that screw.
Don't blip the throttle while the allen head wrench is inserted.

The final adjustment turn on that screw should be clockwise so you have to go a little too lean or counterclockwise at first and then turn it back clockwise making it rich again until it's right.
If you have experience adjusting idle mixture screws on carburated engines and especially multi carburated engines by ear it will be easy.

If the engine decelerates faster than you like after a throttle blip and stalls then it's still too rich at idle or the ignition timing is also too retarded or maybe your car has a really light flywheel and clutch assembly installed.

If your car does not have a working oem throttle body bypass deceleration valve/vacuum limiter than putting a working one in will make the engine decelerate slower as if the flywheel gained 15+ pounds, but if the idle mixture and timing are correct you do not need one to keep it from stalling after a throttle blip.
The decel valve bypasses air around the throttle butterfly during high manifold vacuum decelerations and it has the same effect as not taking your foot all the way off the gas pedal while the engine decelerates.
Old 11-30-2009, 11:43 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #9 (permalink)
Reply

Thread Tools
Rate This Thread
Rate This Thread:

 


All times are GMT -8. The time now is 06:03 AM.


 
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2018, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2018 Pelican Parts, LLC - 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.