Our purpose is to support owners in their use and maintenance of the Porsche 928 and to foster camaraderie among owners throughout the world.
Welcome, Guest
Username: Password: Remember me
Welcome to the 928 Owners Club Forum!

Tell us and our members who you are, what you like and why you became a member of this site.
We welcome all new members and hope to see you around a lot!

TOPIC: Iddle Problems in a Porsche 928S - 1984 Manual Transmission

Iddle Problems in a Porsche 928S - 1984 Manual Transmission 17 Mar 2018 12:22 #20238


  • Posts:9
  • dpagan62's Avatar
  • dpagan62
  • Junior Forum Member
  • OFFLINE
  • Karma: 0
Hello!

I working a restauration of this car since 2016. We complete the body work the last year we were dedicated to the engine. We clean all fuel lines and injectors. We replaced the fuel tank for a new vessel with fuel pump and filter brand new also. We replaced all the fluid and plastic hoses not vacuum yet. We also replaced all the belts the water pump, power steering pump, AC Compressor and the Air Pump also. We turned the engine on a sound peppy but ...... no stable idddle. My car had manual transmission and we start to search vacuum information for Manual car and it limited. In the inspection we found the Thermo Valve with one connector broken also the brake Vacuum Valve also broken. We replaced the brake one and we are waiting with the Thermo valve for to replace it.

What I need? Any of you guys has pictures or clear information of the vacuum hoses and where it correctly connected for my 928S - 1984 Project we are very close to made it but I need the knowledge of the Masters. Remember is a manual transmission.

Best Regards,
The administrator has disabled public write access.

Idle Problems in a Porsche 928S - 1984 Manual Transmission 22 Mar 2018 23:49 #20255


  • Posts:162 Thank you received: 11
  • Rich928's Avatar
  • Rich928
  • Moderator
  • OFFLINE
  • Karma: 3
Is this a US/North American model (has L-Jetronic fuel injection) or European/ROW model (has LH Jetronic)? this makes a difference.
Rich
Membership Chairman
Charter Member
1993 928 GTS Cover Girl
1987 928 S4
1979 928 5-speed rescue
1979 928 5-liter track beast
The administrator has disabled public write access.

Idle Problems in a Porsche 928S - 1984 Manual Transmission 23 Mar 2018 10:46 #20259


  • Posts:9
  • dpagan62's Avatar
  • dpagan62
  • Junior Forum Member
  • OFFLINE
  • Karma: 0
Hey! Thanks for the response it is my first time. My car is a L-Jetronic US version.
The administrator has disabled public write access.

Iddle Problems in a Porsche 928S - 1984 Manual Transmission 25 Mar 2018 05:11 #20263


  • Posts:162 Thank you received: 11
  • Rich928's Avatar
  • Rich928
  • Moderator
  • OFFLINE
  • Karma: 3
Have you made a smoke test (pressurized smoke forced in the intake manifold) to verify there are no vacuum leaks? Any leak after the airflow meter results in "false air" which results in a too lean air/flow mixture.

The L-Jet system has an air-fuel mixture set screw at the airflow meter. The exhaust stream before the catalytic should be analyzed and set between 0.4 to 0.8% CO, an exhaust analyzer is needed for proper adjustment. If there isn't an access port at the exhaust manifold before the catalytic converter, a bung hole and plug should be installed to access the exhaust stream. I had this done to properly set the air-fuel mixture on my 1979 Porsche 928.

Once the air-fuel mixture is set, the idle speed is set. There is a large screw at the throttle body accessed from the front of the engine that is turned for adjustment. The setting is 700 - 800 RPM.

The L-Jetronic fuel injection module requires an accurate input from the temperature sensor and airflow meter to function properly. Make sure that the vane inside the airflow meter moves smoothy.

I hope this helps.
Attachments:
Rich
Membership Chairman
Charter Member
1993 928 GTS Cover Girl
1987 928 S4
1979 928 5-speed rescue
1979 928 5-liter track beast
The administrator has disabled public write access.

Iddle Problems in a Porsche 928S - 1984 Manual Transmission 27 Mar 2018 22:33 #20276


  • Posts:9
  • dpagan62's Avatar
  • dpagan62
  • Junior Forum Member
  • OFFLINE
  • Karma: 0
Thanks again for your answer. The CO meter I found in the internet has 4000 ppm or 0.4 % max any suggestions for a higher range? We installed the Thermo Valve today and installed back the mass flow device but the car remain with iddle very high or accelerated. My mechanic said that he touch the mass flow flap and it reduce the RPM he said that problem is probably there.

I have another question: In the four way vacuum connector that join four Vacuums; It connects the vacuum reservoir, Cruise Control in one leg. A second has the line from the brake buster, a third one is connected to the Vacuum Port inside the Car AC system. My doubt is the fourth line no idea where is the right place to connect it. Not sure has some relation with the iddle problem but this port is not connected.

Regards
The administrator has disabled public write access.
Moderators: Rich928, mm928, billvvOC
Time to create page: 0.904 seconds