Hey all, I've got a 97' Civic DX hatch and it's started doing something weird. I was going over it before inspection and after a few minutes of idling it starts doing this..all I can think of is the PCV valve is gummed up from sitting for the past few months. If anyone has an idea or similar issue, please let me know. Thank you!

Link to the YouTube video (taken with iPhone, sorry for quality.

 

clean the iacv to

 

The engine is getting to much air somewhere, doesn't necessarily have to be the IACV...


Good place to start is a thorough inspection of everything vacuum related on the motor...

Next would be the IACV if nothing turns up...


The reason the idle is bouncing, is because there is a fuel cut at 1500 rpm when the throttle body is closed..(deceleration)

The pause in fuel supply is making it bounce..

 

^

 

I'm new to this kind of stuff..what exactly does "everything vacuum related" pertain to? I know how to clean my IACV, and was going to do that when it warms up.

I'm not hitting the gas at all in this video. That's completely idle without any help from me.

 

vacum lines:anything that connects to the intake manifold a ex is the pcv hose unhook it and watch you'r idle go up. so if you have a "vacum leak" you'r idle would be higher than normal.

 

Not to thread jack or anything but would the FPR being Disconnected cause the same problem?

 

What do you mean by the FPR?

 

fuel pressure regulator. not unless it's shot will it interfear with you'r idle

 

So you're saying that I should unhook the PCV hose and see if my idle goes up? If it does, I have a leak and should replace that?

 

i used that as an example of a vacum line since you asked. getting any codes ?

 

I would definitely try and source out a vacuum leak before disturbing anything like the IACV...


unmetered air will make the engine race.. check all rubber hoses...


I like to use propane to find leaks...

Propane is cold and gets into small spots... It also falls since it is dense, and does not blow away..

I'm also a bit of a hick.... But it works well.... Makes the engine bog down...

 

No codes. I think it's just a dirty IACV or PCV valve. The car sat for a while before I got it.

 

Watched you'r vid that doesn't seem like a VAC leak as it goes up and down if it was a high steady idle vac 100%. But i'd say you're right pcv or iacv give them a clean and see what happens. Wouldn't hurt to clean you'r TB aswell. I assume you'r timing is on(correct)