Re: O2 Sensor Diagnostics

["Paul C. Waterloo" <74543.407@CompuServe.COM>]

>  	If the O2 sensor is wrong, the ECU will be deceived, and the final
>  mixture will also be wrong, which will cause all sorts of drivability
>  problems. 
>   >>
> A better test, paul, is to grab the diagnostic plug (2 prongs green/purple
> and brown) up near the fuel filter....  That gives you the duty cycle of the
> O2 Freq Valve......  You can use a DC meter or a dwell meter (90% X DC =
> Dwell angle on 4cyl engine), the factory spec is 50+/-8 DC, you want to set
> at 42DC or 38dwell.....  A warn O2 will show great fluctuations in reading, a
> new one is more steady for a given reading....  To adj, a 3mm t-handle hex in
> the port between the FI boot and the fuel dist lines....   A turbo car will
> eat an O2 faster than a N/A car, and a bad fuel mixture can eat the O2 as
> well....  60k is pushing it, me I can tell when mine goes south, cuz the gas
> mileage takes a 5mpg plunge, usually 30k or so....
> 
> HTH
> 
> Scott

Scott-

Thanks for the good tip, but after looking for the diagnostic plug, I found I
didn't have one. The 20v turbo did not have them. This is for the old CIS system
(as I'm sure you know). 

However, you have given me a good tip. You mentioned loosing gas mileage. When I
first drove my car home from Chicago, I got 28 and 25.5 mpg (actual by
calculation). My car started to surge much more not long after that. My gas
mileage is now about 21-24 MPG.

However, I did put new tires on at about the same time, Dunlop D60 A2's. I'm
sure that could also change the mileage, but I keep them at about 35 psi. Don't
know.

Paul

91 200q (probably getting a new O2 sensor)

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Paul Waterloo                    TEL: (860) 267-7714
HydroAire Incorporated           FAX: (860) 267-7387
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