93 escort idle problem

I have a 93 escort lx 1.9. After setting at idle for a few minutes the engine will rev up then slow back down over and over. It revs for about 2 secs then dies back down. If you give it a little gas it clears up and
stops. Any help would be appreciated. Thanks in advance.
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I had a van that did that and the ranger does that too.. for the life of me i dont know what it is i dont see it as a problem however.
My new f250 does not do it (yet) i have a feeling that it will some day.
I would like to know what this is as well... what causes it. I mean just stabbing at it ~ can be a sticky choke... but since it is so repetitive in timing it seems almost like an electrical problem.
Kenny

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A bad or incorrect PCV valve can cause this, and is one of the most likely culprit. Take a close look at the air intake bellows as well.

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I had this problem with my 91 Sierra DOHC 2.0i - turned out to be the 02 sensor - don't know if your car has one - on the sierra it was situated under the bonnet on the right wing closest to the windscreen. This may not help but I hope it does.

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