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 > Porsche 911 Technical Forum


Reply
 
LinkBack Thread Tools Rate Thread
Author
Thread Post New Thread    Reply
Registered User
 
Join Date: Jan 2004
Posts: 1
930 engine misfire

I have a 1989 930 that I've had for 2 years. It has been perfect up to a few weeks ago. Since then, on 3 occasions, it will run rough with "wild swings" of the tach. At a constant speed (mph), the tach will indicate 2X the expected rpm, and the engine runs as if on 3 cylinders. I drive home, shut it off, re-start, it runs perfectly again! Then runs perfectly the next half dozen times, then repeats the above.

Problems the DME? Electronic ignition? Coil?

All ideas appreciated!

Thanks. Bob

Old 01-31-2004, 04:53 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #1 (permalink)
Registered User
 
Join Date: Sep 2002
Posts: 3,580
Unless it's wildly modified, your 930 has CIS, so no DME.

It sure sounds like it could be an electrical issue between the CDI/distributor/coil. I'd start looking at the connections in that area. Have you checked the ground cables in the engine bay? Cleaned all the electrical connectors and used dielectric grease on them? You can start with the distributor's 6-pin CDI connector, and the main 14-pin connector.

The CD box could also be failing.

Good luck
__________________
993

Last edited by cowtown; 01-31-2004 at 06:42 PM..
Old 01-31-2004, 06:34 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #2 (permalink)
Registered User
 
rotorhead's Avatar
 
Join Date: Jul 2003
Location: Port Macquarie Australia
Posts: 509
Almost certainly it is the voltage regulator on the alternator. An easy way to check is measure the battery voltage while the engine is running it should read around 13.5-14.5v. If it is much higher then the voltage regulator has failed.

Dont drive your car with high voltage, the engine management system and speedometer can fail.

It is a very simple (2hour) job to replace it
__________________
2008 BMW 320i
2006 Mercedes ML320
2004 Mercedes ML270 cdi
1998 Porsche Boxter
1988 Porsche 930 Targa (sold)
Old 02-01-2004, 06:53 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #3 (permalink)
Registered User
 
beepbeep's Avatar
 
Join Date: Jun 2001
Location: Sweden
Posts: 5,615
Quote:
Originally posted by rotorhead

Dont drive your car with high voltage, the engine management system and speedometer can fail.
Engine managment? :-) There should be some Lambda circuitry there though...
__________________
Thank you for your time,
Old 02-01-2004, 07:18 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #4 (permalink)
Forced Induction Junkie
 
WERK I's Avatar
 
Join Date: Jan 2003
Location: Wisconsin
Posts: 3,300
Garage
I agree with Steve Hall. I had the same problem with my turbo. Mine happened when I turned on the headlights. Engine would misfire and not pull very strong. I removed the alternator and pulled the regulator/brushes assembly. Brushes were worn down almost completely. I inspected the commutator shaft that the brushes ride on and it was worn down considerably. I had to replace the alternator because of the commutator problem.
__________________
Dave
'85 930 Factory Special Wishes Flachbau
Werk I Zuffenhausen 3.3l/330BHP Engine with Sonderwunsch Cams, FabSpeed Headers, Kokeln IC, Twin Plugged Electromotive Crankfire, Tial Wastegate(0.8 Bar), K27 Hybrid Turbo, Ruf Twin-tip Muffler, Fikse FM-5's 8&10x17, 8:41 R&P
Old 02-01-2004, 09:25 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #5 (permalink)
Registered User
 
Join Date: Sep 2002
Posts: 3,580
Hmmm, interesting. I've never heard of an intermittant VR failure, but maybe it's a heat-related thing? It's cheap and easy to check the voltage, I guess.
__________________
993
Old 02-01-2004, 09:28 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #6 (permalink)
 
Registered User
 
rotorhead's Avatar
 
Join Date: Jul 2003
Location: Port Macquarie Australia
Posts: 509
The reason I said engine management is that if your car has DME then (I have read on this forum) that high voltage can fry the DME. But as rightly said before you 930 has CIS.

Does anyone know where I could learn more about CIS?

__________________
2008 BMW 320i
2006 Mercedes ML320
2004 Mercedes ML270 cdi
1998 Porsche Boxter
1988 Porsche 930 Targa (sold)
Old 02-01-2004, 04:19 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #7 (permalink)
Reply

Thread Tools
Rate This Thread
Rate This Thread:

 


All times are GMT -8. The time now is 11:01 AM.


 
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2020, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2020 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.