CIS help?

Konstantine Bogach kbogach at
Wed Dec 10 13:59:18 EST 2003

Having problem with CIS I followd Orin's advise and tried to adjust air/fuel mixture so the measured OXS output voltage, while it is disconnected from ECU, is ~0.5V.  I could not do it.  Voltage jumping all over the place. I can get to the point - makig it richer - where voltage stay stable at ~.87V.  Slowly making it  leaner
gradualy(but very small change in the screw position) reaches ~.75V and then goes to the state where voltage randomly jumps betwee 0.004V to .9V.  Going far to lean makes voltage stay at ~.001V.

Does OXS voltage should stay more less at same level in whole voltage range while signal wire is disconnected from ECU?
I think it should. Then I can think of 2 possible problems: 1) bad sensor; 2) bad/intermittent combustion causing big variation of O2 content in the exhaust.  Making not very educated guess, the latter might be caused by bad spark or not good fuel mixture atomization.

Any advise of comments are appreciated as always.

Two 200tq '89 run well but failed CO test.

> >Measure the O2 sensor voltage with it disconnected from the ECU and
> >set the mixture for about 0.5V... then see what the duty cycle is.
> Ahhh, good idea.  I hadn't thought to try that.  I'll do that when I get home.  That should give me a halfway decent idea of where the mixture is.
> Greg Roa

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