Civic '90 DX 4dr - O2 sensor and PCV valve

At @140k miles, will replacing them improve engine performance at all? I pinched the hose going to the PCV and no clicking sound like the Haynes manual described there should be. The hose just collapses flat like straw in
a vacuum. And how do you know if your O2 sensor is working the way it shoul be?
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precambrian wrote:

Many shops replace the PCV valve at 60,000 mi intervals. Many folks also have success with removing the valve and cleaning it with carburetor cleaner.
Eric
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At 140k miles and16 years, replacing either the O2 sensor or PCV valve or both may improve performance. It's not guaranteed. OTOH, the parts are cheap enough to warrant replacement about now.
Did you pinch shut the hose to the PCV valve and wait at least 30 seconds, listening to the click? It's not terribly loud, but it is noticeable. With the engine off, you should also remove its hose, then the valve, and inspect it. When I did my 91 Civic at about 138k miles, I found the valve top chock full of black waxy buildup.
I would just replace the PCV valve at this point. Its springs, for one thing, do wear.
One other benchmark type test: With the engine idling, remove the hose from the top of the PCV valve, then cover its top with your finger. You should be able to get the "click" this way, too, on your 90 Civic.
Best prices for genuine Honda (= OEM) oxygen sensors (IIRC around $45 for your car): https://www.automedicsupply.com /
Best price for a PCV valve: http://www.hondaautomotiveparts.com/auto/jsp/mws/PartsSearch.jsp http://www.slhonda.com Click on "Parts and Service," then "Buy Parts Online."
With shipping, buying the PCV valve at your local dealer might be a better deal.
I replaced my 91 Civic's oxygen sensor pre-emptively at 154k miles. I didn't notice an improvement in performance. On the other hand, I probably won't ever need another oxygen sensor for this car and so have avoided a sudden failure of the oxygen sensor (which admittedly is not devastating; just annoying).
A few symptoms of a failing oxygen sensor are degraded miles per gallon and engine running rough. There are voltage tests one can do on it, too, but I think that's overkill for an older car.
Only buy OEM for these parts.
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