Post #1:
Quote:
Originally Posted by massmike
Looking for some help to solve a problem I have been chasing for a few months now. Car is a 1982 911SC with a 3.0L and the original CIS system. My issue is when the car is running in closed loop there is a light surging at cruising speeds. The surging can't be seen on the tach but I find it incredibly annoying to drive it like this. If the O2 sensor is disconnect the surging completely goes away, so I believe this problem is limited to the Lambda system. I do have an LM-2 wideband connected and with the O2 Sensor disconnected I see 14.3 - 14.5 while cruising, O2 sensor connected I see it jumping between 14.3 and 15.3 at the same RPM and speed range.
I have replaced the O2 sensor and the FV relay, both made no difference. I have also adjusted the mixture several times with no noticeable change in the surging. I am thinking possibly an issue with the Lambda ECU??
Any help would be greatly appreciated.
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Your data from your first post is potentially insightful. It indicates your warm control pressure may be a little too low (causing a too rich a mixture).
An upstream post suggested checking the warm control pressure. Have you checked it to the posted WUR specs?
This can potentially contribute to the closed loop O2 system developing a greater Lambda correction - surging,
as the system attempts to over-correct (15.3)
To lean the mixture, the pin needs to move up.