So, this little problem is kinda annoying, I will be driving around and if I rev the car up or past 5,000RPM and let the idel drop it will go about 400+ lower than it ideld before going up to 5 grand...? Its weird, is there a way to fix it?

 

It happens to my car too! It feels like it will stall, but then seems to recover itself... I cant think of any way to fix it though, but it seems a few people have this problem and its normal

 

Well it doesnt recover, it will stay at a low idel usually around 6-800. Just recently I would be driving and it would almolst stall but correct itself, and I replaced the cap and rotor on the distributor and it fixed that. But maybe it is normal... Its a 16 year old car, after revving up to 5,000 maybe it needs a break I guess lol.

 

The IACV might be a dirty.

As well, I was experiencing the same issues with my '95 VX, and the problem is now gone after the work I did this weekend. Of course, I'm pretty sure (not entirely sure) the big problem was because I forgot to plug the PCV back in when I rebuilt the engine a few months ago. I don't recall having gone through the major PITA of getting it back in last time, and the car runs like a champ now. That's about the only thing that came out different this time.

If your PCV is dirty and/or clogged, it will cause the ECU to over-compensate by dumping in more fuel... which will run a bit richer than normal, and can cause the excessive drop in rpms when it tries to settle down after being in the upper end of the tach.

 

I got a IACV for free that fits a civic but it is different from the one on my engine?? Is the ZC IACV different from the stock civic IACV???