1974 1.8 Light Load Stumble |
|
Porsche, and the Porsche crest are registered trademarks of Dr. Ing. h.c. F. Porsche AG.
This site is not affiliated with Porsche in any way. Its only purpose is to provide an online forum for car enthusiasts. All other trademarks are property of their respective owners. |
|
1974 1.8 Light Load Stumble |
andrewvolsen |
Jan 24 2017, 10:17 AM
Post
#1
|
Newbie Group: Members Posts: 44 Joined: 6-December 09 From: Santa Barbara Member No.: 11,099 Region Association: Central California |
My '74 1.8 L-Jet 914 has developed a light load hesitation/stumble. It is the most pronounced when cruising on flat ground with light accelerator application, maybe 10% opening of the butterfly valve. The stumble is not noticeable when accelerating.
The car has: - New vacuum lines - New plugs, wires, cap, rotor, and coil (still running points) - Cleaned throttle body and checked operation of TPS - New accelerator pedal and throttle cable - Rebuilt MAF - Recent valve adjustment Does anyone have any suggestions for how to proceed with diagnosing the cause of my light load stumble (IMG:style_emoticons/default/confused24.gif) |
scott_in_nh |
Jan 24 2017, 12:08 PM
Post
#2
|
Senior Member Group: Members Posts: 808 Joined: 10-December 10 From: Hampton, NH Member No.: 12,471 Region Association: North East States |
By chance does it happen right around 2k rpm?
If so you may need a slight adjustment to the TPS. If the ECU thinks the throttle is closed above 2k rpm, it kills the fuel to the engine. When/if the engine hits 2k rpm, it adds fuel again. When the TPS is misadjusted, you can be trying to do a part throttle cruise, but the ECU cuts in and out with the fuel. If it is happening above 2k rpm, you may have a lean condition requiring a slight tweak of the MPS. |
porschetub |
Jan 24 2017, 12:11 PM
Post
#3
|
Advanced Member Group: Members Posts: 4,697 Joined: 25-July 15 From: New Zealand Member No.: 18,995 Region Association: None |
When was the last time the distributor was cleaned ?,is the advance plate moving freely under vacuum,pull the hose and suck on it ,it shouldn't take much effort.
So many of these distributors are gummed up after all these years. Also check your timing to see you are getting the correct maximum advance ,and your timing is correct @idle. Good luck. |
Lo-Fi Version | Time is now: 25th April 2024 - 04:19 AM |
All rights reserved 914World.com © since 2002 |
914World.com is the fastest growing online 914 community! We have it all, classifieds, events, forums, vendors, parts, autocross, racing, technical articles, events calendar, newsletter, restoration, gallery, archives, history and more for your Porsche 914 ... |