924Board.org

[924-76]

Not sure I understand you correctly, but to be clear, number below 14 A/F is rich and above is lean.
When you read 9.8, that is rich and yes this could be an indication of a faulty O2 sensor.

I had an occasionally faulty O2 sensor, car would run and drive well and studently went rich for no apparent reasons. Ask me why I run the car without O2 sensor lol. I unplugged it, readjust the A/F at the fuel distributor and never had problem past that.
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1976 924 N/A ROW SOLD
1980 931S
1981 931 Part car RIP

[MikeDanger]

[924-76]

[MikeDanger]

[MikeDanger]

Finally got the car in the garage, but havent had much time to test.

What I did so far is test the O2 sensor. after the car was warmed up, I unplugged it. engine rpms rose slightly. I checked the voltage and it was putting out .42V The FV didnt seem to cut out after 10min of idling.


I was looking on the 911 forums and Found the Bosch K-Jetronic Manual.
One Mention was to check the Oil Temp sensor....does the 931 have and OIL temp sensor?

Also Im wondering about the Thermo Time Switch?
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It was either this or a giant box of legos

[MikeDanger]

Finally got to do some testing.
first tested the O2 with the engine warmed and running and got initially 0.43v and after aboout 30min of running went to 0.39v

I pulled the cover off the connector and here are the readings

#8 11.5v
#12 10.6
#15 8.3v-9.0v
#17 2.95v

AT the FV the Brown/Y wire 9.2V
Black/Gn wire 11.6

also I pulled connector off the throttle switch, and the Idle Jumped up. which might be expected.

Also I unplugged the Other "silver box" next to the Lambda unit, and it responded just as if I had unplugged the labmda.

At one point, once the FV became intermittent and weak sounding, when I would crack the throttle, the FV would come back.

Now heres another possible thing I think My alternator is a little weak could that have anything to do with it?
Reason i ask is that now the FV is running full time when I flip the Fuel pump switch (where as previously it would only run for a few seconds) (but I had the charger on and in the "engine start" setting)
The other thing is that ambient air temps were a little colder wonder if it is some Temp related issue, might that have anything to do with why the FV was running longer this time.
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It was either this or a giant box of legos

[MikeDanger]

Update tonight, I started the car, FV was running Fullly, AF was "in the green" then after 5+ min the A/F went lean, and the idle dropped, FV was still running but weaker, I decided to test the O2 At the Computer, it was fluctuating quite a bit.
Then i went under and disconnected the o2 and the idle came back up, and the A//F was in the green, slightly rich around 12.5 but steady.

So im just going to order one from amazon, since they are only $11 (bosch 11027) and see what happens!

I think im also going to wire in either a switch or connector on the O2 wire in the cabin so I can "turn off" the O2 sensor.
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It was either this or a giant box of legos