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One for the Sensor Gurus


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Here we go....

1993 4.9 Deville 111,000 miles, No codes, no surging, slightly rough idle, Mileage on highway almost the same as city.

I replaced the O2 sensor about 40k miles ago. While looking at the OBD readout (P.17 ? O2 Voltage, I forgot) on the highway just cruising it will vary between .20 to .70 if I let off the gas it will go to .05 or less and stay there. If I step on the gas too long it goes to .95 or more and stays until 5-10 seconds after I let off the pedal. I would figure the ECM would manage the fuel butter than that.

This doesn't seem normal to me and my question is, should I change the O2 sensor ? Could this be caused by TB Cleaner from when I clean the EGR Tubes (every other oil change ?)

My injectors and FPR do not leak (i checked)

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Thanks, very informative !

But you are going to kill me

One other question about the ODB info, how do the crosscounts work and what can you tell from them ?

And O2 sensor are good for 50k, correct?

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The more "cross counts" you see, the better the O2 sensor is working. The actual voltage reading the O2 sensor would display given the 14.7-1 AF ratio is .440 mV. The computer "counts" a "cross count" every time it detects a jump in voltage from under .440 to over .440, or vice versa. Generally, you should see equal changes both below and above .440. You will not find the O2 sensor hovering at exactly .440. It is normal for it to go from "one side, to the other".

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