Hi, i recently got a Civic 94 EX and it's been having some idle issues. I've search around here and from what i gather, it seems it could possibly be either a clogged IACV or a vacuum leak maybe. I've also seen post where people claimed it was "normal" for a older car but being a owner of a previous EJ1 with more miles, i'm not buying that. I couldn't find a post where a rough idle problem affected the heat or air so i figured i'd post. Apologies in advance if this is annoyingly a repeated thread. D:

This is my second EJ1 so im sorta familiar with the car. The first thing i did was flush the coolant system through the block and replaced the coolant and refilled, using the bleed bolt to be sure there was no air in the system. There is no leaks in coolant, etc. The heat blows extremely hot, but sometimes prior to starting the car the heat stops for a moment then continues. Sometimes more than once, but i've never noticed this once the car warms up and i'm driving. Also, more times than not, the car will idle roughly once it warms after start (in Park) and there have been times where it's done this and once i've arrived at my destination, and placed the car back in Park, there is no rough idle. Also there have been two instances where i was stopped at a red light (and while in Drive) the RPM's went up and down much like rough idle (embarrassing). Both times it ceased even before the light turned green.

The engine is a VTEC D16z6 with 154,XXX miles on it, no CEL. It's pretty great on gas, as a full tank lasts me about 2 weeks even commuting to 2 jobs and school. I found a post explaining how to clean the IACV, which i plan to do in the morning. I figured with the symptoms affecting the heat/air, logically, it must be a vacuum leak, no? But, i'm no expert at cars so, any ideas?

 

sounds like u have air in your coolant system.... park the car on a incline(or jack it up) making the radiator the highest point let the car run with the cap off until the car fan comes on times... add cooant if needed

 

Thanks for the response but I've done that.... In fact it's the first thing I did as explained in my original post. The car has been parked on an incline, and coolant flushed, bled and refilled.

 

Have you cleaned the IACV? It is VERY easy. Did it in <30 minutes and it eliminated all of my roaming idle issues instantly and my car almost seems to run a little smoother sounding. Get some carb cleaned disconnect everything from it and get it out of there and just spray the two holes for up to 15 minutes until the fluid drains out completely clear. Let it air dry face down so any excess cleaner drains out and bolt it back on and reconnect hoses. I was amazed how so little work made such a change in the operation of my car.

 

Coolant doesnt have anything to do with your issue.

Take some carb. cleaner and spray around the intake manifold , look and listen for a drop. If this happens, you have vacuum leak. The open hose is sucking in the carb. cleaner causing the engine to miss fire. But make sure you DO NOT use that crappy azz advance auto parts carb cleaner. I recommend 2x2 carb cleaner. Carb. cleaner is pretty much a type of gasoline PURE ALCOHOL with i think cleaning additives. I have no clue what advance auto parts crap is that they try and pass off.

Anyways, if it is the IAC , its stock shut. If it were stuck open. Your idle would be around 1500 rpm.
You can clean it with carb. for mentiance but im almost positive its a vacuum leak with the idle fluctuating.

If the IAC is clogged or stuck shut, i recommend taking pb j to it , let it sock for about 10 mins or so and then clean and rinse a few times until its spitting out clear carb cleaner.

If you just use carb. cleaner it will help for a hot min but after driving it the sot will more than likely heat up and clog it again because you can really get a brush into the two port holes and scrub it ( ONE PORT HAS A SCREEN IN IT ANYWAYS). Ran into this issue a few weeks ago.

 

Thank you apexi rsx,I was expierencing the samr problem-Fixed

 

Nope, was suppose to clean it this morning but woke up too late, so im waiting for the car to cool down now as i just got home from work. Once it cools i was going to clean it up with a small wire brush and some simple green. Hopefully you're right and the idle issues will vanish.

 

I've had the same issue with my last EJ1, but it was in fact due to a blown HG. The combustion chamber was leaking into my coolant so all the air was causing rough idle (Which ceased after i replaced the HG and bleed the air out.)Ofcourse that isnt the case now though.

On the drive home from work i figured i'd check a few things to keep this post updated. On start the car actually does idles in park @ 1500 rpm's (more or less). In Neutral and Reverse it idles @ 1000 rpm's. In drive it's @ about 1200 rpm's more or less depending on whether i let it coast or apply brakes. It stayed this way once it was warm and today seemed to be one of the rare days i didnt get the rough idle (low and high rpm's). Usually when i get the fluctuating idle it starts off @ around 1500 rpm's and drops to 1000 rpm's and back and forth respectively. It was pretty warm today so didnt have the heat on, not sure if there would have been a difference. Once it cools off i'll clean up the IACV, and reset ECU to see if there's any changes.

 

Then its your IACV, my car idles around 1200 but its not to the point that i want to spend 250.00 for a new IAC.

I just cleaned the **** out of it with PBJ and then rinsed it with 2X2 Carb and bite my tongue , hasn't tripped a code yet.

 

Been a busy week.... So a few days ago i did manage to find time to clean my iacv or atleast attempt to... For some reason one of the bottom hoses refuse to detach from the iacv(with clamp removed) so i was forced to do what i can with the hose still attached as im a bit scared of damaging the hose... After doing what i can, reattaching the iacv, resetting the ecu and starting the car up it idled at about 900 rpm's.... Rough idle vanished for the days following til today... Today after work, @ 900rpms with the car idling as i pressed the brakes to shift the car began to idle roughly.... Eventually the rpms got so low the car stalled.... No CEL or anything... For a minute or two i couldnt get the car to start... My guess is lack of oxygen.... After inspecting the bay i noticed there is a tear in the hose from the intake to the engines valve cover (breather hose?)... Also theres a slit in a hose connected to a L-pipe.... Im not sure what the function of these hose are but slits and tears cant be good.... Guess i'll buy replacement hoses in the a.m..... Im not sure how to go about attempting to clean the iacv again... I wouldnt be so worried about possibly ripping the bottom hose if it wasnt in such a awkward spot that replacing it was be difficult