My car, after warm up idles from 1000, 1500, 1000.... Also when it's running "normal" if I turn on the lights, or hit the brakes or even move the shifter from 'P to 'D', the RPM's jump for a moment from 1000 up to 2000. I have not done anything to fix this. I'm not very good with accronyms and I'm not a mechanic. So please explain it to me as if I don't have a clue about cars. My vehicle has had the engine replaced, don't know what kind of engine is in it now (and don't know how to find out either)

 

check for a vacuum leak..when you start the car up listen for a hissing sound and see if you can find where it is..look at lines, gaskets etc.. if your not very mechanicly inclinde i would just take it to a shop

 

Sorry for the long reply back. No hissing sounds, I did replace my PCV. The problem is getting worse now. Now when I'm driving the RPM are contually high, when you put in Neutral, same thing as before, 1000-1500 oscillations. I'm really trying to fix this myself, to save $$.

 

Is the motor revving up and down quickly or slowly creeping up? Does it keep doing it or just once? If it's only momentary, don't worry about it. The tachometers have been known to be severely inaccurate in these cars

To check for vacuum leaks, your best bet is just pinching them or pulling the hose off and blocking both ends with your fingers.

I subscribed to this, keep us informed.

 

What engine is currently in the Civic?

I would try cleaning and adjusting the fast idle valve (FITV) located on the throttle body, and also bleeding the cooling system:

Bleeding the cooling system

1) Park the car on an inclined driveway with the front end higher than the rear.

2) Push the dash heater lever/**** to MAX heat.

3) Follow the directions in the diagram below (hint: the bleed bolt is located where the upper radiator hose connects to the engine):

 

VACCUUUM LEAK TIME CHNAGE GASKETS TB N INTAKE MANIFOL

 

I say a bad Iac, its that big thing behind the intake manifold held on with the 2 12mm bolts and 2 coolant tube on the bottom. but before you change out the iac, just to make sure, try adjusting your idle adjustment bolt by the top of the throttle body with a flat head, turn it all the way down first and your idle should calm down to a point where it wont bounce around.

 

The oscillations are fast and continuous. The car is an LX but my wife had the engine replaced before she met me, she is saying it's an EX engine. I do know that it's not an LX engine, cause the PCV is bent 90 Degrees, the one that I ordered (LX) at Autozone was straight.
I will perform the checks mentioned so far (on Saturday) and will keep everyone updated. Thank you all again for the info.

 

take it to a shop