dude_uuk

Hello. Just want to ask what can be the probably cause why my RPM plays from 2000 and then back to 1000 RPM whenever I don't use the aircon and in neutral position. Can it be the throttle body? Please advise as I am at a lost right now. Hope you can advise me with your expert advise. This is for honda civic vtec 96.

Thanks in advance.

robbys89

any cel light? were you playing around with the engine before this happend? check your idle control valve bolted behind the intake manifold. make sure your full with coolent

adams90crx@msn.com

Could be and intake manifold leak. I had that problem when I upgraded to a Skunk2 manifold. If the gasket is not fitted properly that will happen.

IIXtremeHansen

Got a CEL?

trustdestruction

Check your IACV and FITV (idk if you have one) for dirtiness and possibly even being broken. Maybe check your PCV valve (if you have one) too. Look for vacuum leaks.

K_Spec98R

Could be your idle valve solenoid sticking happened to my old eg

Redbone

IACV most likely or vacuum leak in the manifold, check for vacuum leak first

dude_uuk

Hi guys, thanks for your replies. My check engine is lighted but it doesn't happen when it is lighted. It is intermittent. When my RPM plays I just turn the aircon on and then off and it goes away. Does this has anything to do with the knock sensor? because right now, i don't have mine bolted in. It was broken and will replace it by next week.

munster87

It shouldn't have any thing to do with your knock sensor that's probably the reason for the CEL. I would look at you IACV, TPS, and possibly your MAP sensor.

dude_uuk

hi guys thanks for all your comments. I have a couple of questions more:
1. When I accelerate and then I release the gas pedal, my RPM goes from 2000 and back to 1300 and then back to 2000.

2. When I shift from park to drive (mine is vtec '96 auto), it also goes to 1500 back to 900.

3. When running, say 60KPH or any higher speed, and then I release the gas pedal my RPM goes down to 1100. This is odd, right beacuse it should stay high because I am running at high speed and I am not idle. And when this happen, i cannot accelerate fully as the engine seems to not respons fully. This happens once in a while.

I think all these are related but I don't seem to know where to start looking. Can someone teach me how to diagnose these problems? Just to know if something is really broken and needs replacement. My car is all stock and havent modified anything aside from intake filter. And I just had my piston rings and con-rod bearings changed as well as timming belt and tensioner bearing.