adam

I've been looking into my rich air/fuel mixture settings.
I replaced the O2 sensor because it always read .4 v (never changed at all!)
Now, the new sensor likes to sit around .7 volts

While driving it will sit there. If I'm playing with the throddle, it will
lean out (0 volts). With acceleration, it does stay at .7 volts.

If the computer is supposed to try to get it to .45 volts, then I guess I
need to check the carb to see if it is not able to make the mixture that
lean.

Has anyone else watched the sensor reading while running? Should it sit
at .7 v, or should it be clser to .45 v with the computer adjusting it?

Thanks.

stickboy

I would check to make sure that your ECM is working. If the mixture is off you should be getting a check engine light. To check your ECM, turn the ignition on but don't start the car, if the check engine light comes on, then your ECM is ok, if not you need to find out why. If the ECM is not working, your car will still run, but the mixture will be off and you will be running with a fixed advance.

adam

Hi Stick;

The ECM does work - I've gotten codes from it, the check light does work, etc.
I presume that the carb is not able to lean out the mixture enough to drop
the mixture to the proper level. Either that or it its sticky. I had
problems with the fast idle getting stuck, so I guess I'll be looking at my
carb to see if I can clean up that area.

Thanks.

stickboy

Are you testing this at idle? The engine is supposed to run a little rich when it is idling. Also check to make sure your choke opens the whole way. It is supposed to be fully opens in about 3.5 minutes. If the ECM is funtioning properly and can't get the mixture right, then your Check engine light should be on.

bigvette1

What kind of dwell are you running on the T/P for the Mixture control solenoid? After fully warm it should show some cycling when you goose the carb. Check it out and see if the ECM is being fed info that is forcing the MC rich.

UKPaul

I haven't looked at the system I/O voltage readings (yet!), but when checking these '81 systems out, bear in mind that the computer seems to have a fairly wide error margin regarding O2 content in the exhaust b4 it flashes the Check Engine light.
:cheers:

adam

Hi Paul;

I would expect that the computer would have margin, but given that the
sensor range is fairly small, it should notice a 0.2 volt difference (20%.)
I'm going to get a dwell meter to see if I'm getting a swing on the mixture
solenoid. Other than that, I'll have to think about taking the carb off and
checking it out - I still have the fast idle cam sticking so maybe there is
another place where something is sticking too.

Thanks.

UKPaul

Hi Adam,
I'd be very interested in seeing what dwell figures that you get (esp. @ idle).
Good luck (these ECU controlled carbs can be a nightmare until you sort it out - then it all makes perfect sense! :) )
:cheers: