Hi all,

It was cold last night(well for Texas standards), it was down in the mid
teens. Anyways, this morning, went to start car, started fine... then
after the car warmed up, notice the idle was surging/cycling, between 900-
1700rpm, continous. Pulled over, looking for any problems, couldn't see
anything out of the ordinary. This is on a first gen b16 in a 91 CRX Si, running PR3 ECU. Car warms up
fine... and drive fine. The only other thing I noticed is that when I
shift, the rev's will stay there for about 1-2 seconds then start to fall,
as if the throttle was stuck open... any ideas would be greatly
appreciated.

thanks,
-Shing

 

You could have a vacuum leak, or a bad IAC valve.

 

This may help.
https://honda-tech.com/zerothread?id=135165

 

If you take out the idle adjusting screw you'll see carbon caked up on the tip. Clean the tip and inside the chamber that the screw goes into. I've had a few Hondas with this problem and I've done the above. Haven't had any come back on me so I now the problem was fixed. This is pretty common on older Hondas. Make sure you measure the depth of the screw with a caliper before taking it out. You'll probably have to fine tune the idle even though you've measured the depth. Also, if you take off the IAC you'll see a thin build up of carbon on the screen - clean it. You very well could have another problem, but figured I'd throw in my 2 cents.

 

On the throttle body. Check your Helms for specifics.