Rich stop on '86 4 ksq

[Huw Powell]

I'll dig out the doc. references later, I have the Probst book.
Attachments get stripped before they hit the list.

(since typing that I got the relevant picture, looks like page 28 of
Probst)

> OXS fluctuates 0.5-0.7 V
>
> At 3000 rpm is steady 0.8 V

it's not working.  obviously something is amiss, but you knew that
already.

since there is no way an OXS can read a steady .8 volts in a closed loop
feedback system (it would have to be constantly getting a perfectly
slightly lean mixture), the .8 volts is either a bad OXS or a spurious
voltage from somewhere.  if you disconnect the OXS you can read the .5
volts on the ecu at that point.

So.  The ecu thinks you are running lean, and it maxes the CPR current.
you end up running rich.

You might have an air leak in the exhaust prior to the OXS, but I doubt
it.

i think you have a bad OXS or wiring to it, you cna try this.
disconnect the OXS.  measure its output, and adjust (if you can) the
engine at the static screw from rich to lean - does the OXS output
change?

Also, you can apply voltage to the ecu input to see if it affects the
CPA current.  low voltage should get it to increase, to try to lean it
out, and vice versa.  low voltage would be, say, ground it (0), and high
would be around .9-1.0 volts.  a half dead remote control cell might
work for that.

> Does it detect rich condition?
>
> Is the ECU not able to correct (react) accordingly?
>
> When I measure the differential pressure regulator current I do not use a
> harness but simple set up:
>
>       - a wire between the harness and the regulator
>
> -         The second contacts are connected through multimeter (digital)

sounds right, thanks.

--
Huw Powell

http://www.humanspeakers.com/

http://www.humanthoughts.org/