If you have a quality volt meter you can test sensor voltage output. I presume the sensor is on the manifold and there are no air leaks that would cause a lean reading. This test would tell whether it's not the problem. 

Chris.

Wysłane z iPhone'a

Dnia Jul 23, 2014 o godz. 18:39 Don Hanson <dhanson928@GMAIL.COM> napisał(a):

>  Hi all, 84 vanagon, inline Jetta 1.8liter running on Digifant system,
> same as the older Vanagons.
> 
>  Ok so here's the symptoms and the pertinent back story, if someone could
> send me after the right fix I would certainly appreciate it..
> 
>  I recently replaced my 02 sensor and fixed a loose vacuum line and the
> engine has been running great...until just now.   It began running very
> rough, but running smooth again for a few seconds after turning off the
> ignition and back on...So I 'nursed' it home and put it up, crawled under
> to check the O2 sensor...the last thing I fixed...Sure enough, that O2
> sensor plug (flat, four prong) was partly loose...re-plugged it and
> ......after a few seconds, it again began to run really rough again and it
> smells really rich.  Turn it off and on....smooth for a few seconds and
> back to rough....    So, I unplug the O2 sensor plug, re start and it stays
> smooth....
>    So me thinks I have a problem involving the O2 sensor (it was a new
> one, I installed it about 400 miles ago only) or one of the wires or
> something that gets a signal from the O2 sensor...What the heck should I
> began with here?...I did use some contact cleaner and make certain the plug
> connection is good.
>   I am about to go out and open up my wires between the plug and the
> sensor to check and make sure those splices are good...Is there anything
> else that may be causing this?  Oh, I also checked that the ground wire for
> the O2 sensor has a good connection.   Yes it seems to.
> 
>    Help.   I don't want to run with a disconnected 02 sensor because I
> have been getting such great gas mileage since I put the new one in....2+
> mpg better than before I replaced it.    Oh yes....messing with the
> throttle switches and the connections on the Temp II sender, that makes no
> change in how it runs...
> 
>  Don Hanson