o2 Sensors on the Road

89 Sable o2 sensors on the road / EMISSIONS o2 Sensors on the Road

Can emissions failures/defects be diagnosed with QCSC DAS? YES

The 1989 Sable with dual oxygen sensors runs good and gets good fuel mileage, but it is not perfect.On a road test, at a steady, moderate cruise, we see that the o2 sensors are in good shape.

The total time period is about 7 seconds, each grid mark represents 1 second, we can see each o2 sensor switch about once per second, this is good. The o2 sensors are capable of making the rich-lean switch in under 0.200 (200ms) seconds, which is good.

Next we accelerate and then back off while still on the road at moderate speed. The engine controller performs a fuel-cut when we back-off, but look at the right/rear bank oxygen sensor labeled o2#29.

Again we crowd the accelerator and then rapidly release the throttle and the ECA performs a fuel cut, but the o2 on the rear bank shows some fuel is getting through. Typically, Fords do not allow purge on decel, because to do so would cause unnecessary emissions. The most probable cause is a drippy injector on the rear bank.

It is common engine management strategy on late model FI vehicles to perform a fuel-cut on decel. Thusly you can use your scope to find marginal injector drips as long as you aware of factors that could cause false indications, such as, purge system, air pump strategy, tps bounce, fuel dilution, etc.

Always read the oxygen sensor(s) as part of a tune-up, driveability diagnosis, or emissions repair.Basically, good o2 activity equals low emissions and good fuel mileage.

For more info, call: Quad Computer Systems Consultants, 973-472-0328, ASK FOR DAN
EMAIL to; qcscdas@aol.com or; lody@delphi.com or; danbuckley@worldnet.att.net
Please entitle email inquiries -- QCSC DAS
Please visit; QCSC at Delphi or; QCSC at AOL or; QCSC at CIS
or visit; Dan Buckley at ATT or; QCSC DAS at IDT or; QCSC at hometown

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