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We're just finishing up our 3.4L conversion ('97 single-cat. engine into an '89 4Runner) and I had a quick question about where to position the O2 sensors in the exhaust. The exhaust shop has already installed the 1st sensor just after the cross-over, pretty close to the driver's-side exhaust manifold. Does it matter where the first O2 sensor is located, as long as it's before the cat? They didn't install the second sensor after the cat. because the harness wasn't long enough. Is it OK to cut and lengthen the O2 sensor leads?

I'm going back to get the exhaust finished tomorrow morning and would like to know if we need to move the 1st O2 sensor and/or move the cat.
 

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Before the cat 'should' be fine, check with a smog ref to be sure though.

It should be fine to lengthen the wiring for the rear 02 sensor, just make sure you do it right (solder,heatshrink) and run them far enough away not to melt the insulation and so they don't rub through

Andrew
 

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The first O2 sensor should be in a place where it will read the exhaust from both cylinder banks and not just one.

Never cut the wires on the O2 sensor and lengthen it there. You will find that some odd metal is used and you will have trouble getting the solder to stick. Then you may have a problem with dissimular metals being joined causing a voltage change in the sensor signal wire.

If you must lengthen the wires to get everything to reach, do so on the vehicle harness. That is regular copper wire and it is much easier to work with.

Gadget

www.GadgetOnline.com
 
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