Long story short my dads buddy brings me his 2000 Civic EX (Automatic) that is having idling issues. First thing I think of is the IACV as its going up and down between 1k to 2k rpms in typical Honda fashion. Well I get a good working IAC off a buddy and toss it on thinking everything would be good to go. I was wrong lol, the idling issue still persist. Well while listening to the motor run we hear a strange hissing sound coming from somewhere on the manifold.

We start playing around with vacuum lines trying to see if its a bad hose. While playing around with hoses we discover that if you press the hose that goes to the black box on back of motor the idle straightens out. So we crawl under the car and check that line out, find out that its collapsed. So we pull it along with the PCV valve out to inspect it further. Upon removal we find that the PCV valve is no good (doesnt rattle when you shake it and you cant blow air through it).

So off to the autopart store I go to pick up a new one. Come back, reinstall it and again think everything should be good to go...again I am wrong haha. The hissing sound is still there, I am about to go get some ether and start spraying around the manifold in hopes of finding the culprit for the sound. Has anyone ever had this happen to them before?

 

Take off the heat shield on the exhaust manifold and see if it is cracked.

 

Yea try spraying your intake mani with brake cleaner

 

not even gonna read the article .. my brothers 2000 y8 had a weird hissing sound kinda sounded like spool on a turbo .. it was the air cleaner sucking in air through the middle of the filter and making it whistle .. it could also be something loose on ur intake manifold

 

You should of read the article that's not his problem.

 

hissing is most definitely a vacuum leak. probably where the intake manifold meets the head. it can be a bitch to find exactly where the leak with just one person so get a buddy. sometimes when you run the car and then turn it off you will hear the hiss, so it can give you an idea of the area. to pinpoint the leak exactly use brake/carb cleaner and spray in suspected area's. make sure to even check under the IM and on the side's behind the timing belt or near the thermostat. also check to make sure the vacuum hose's on the back of the IM are intact.

 

Maybe there is a hidden rattle snake in there.

 

yes or witches screaming

 

Figured it out. Honda really did some dumb **** here folks. On the 99-00 Y8 manifolds there is a "Air Jet System", that pushes air into the injectors through these little holes on the manifold. Well if you happen to have a 96-98 Y8 head this hissing sound will occur. I learned this through googling and there are several people that show the exact issue and how to fix it. You have to pull the manifold off and either put a 96-98 y8 manifold on or plug the holes in a similar manner to an LS/Vtec. The owner of the car called me today and told me that his nephew (previous owner) had changed the head out, so I started looking at the head and its stamped with a 95 which means its a 96-98 head (specifically a 96 EX)

"Another important note is that the 99-00 Y8 had what Honda calls "Cold Start Assist" I found out my intake Manifold wad from a 99 when the Intake Manifold gasket I got for a 96 left a huge vaccum leak between the head and manifold. The Cold Start Assist has 4 tiny holes on the flange of the manifold, which go to a vacuum line leading to the thermostat housing. I did not even try to bolt the Y8 thermostat housing on my D15b7 Block. I capped off the plugs on the intake and called it a day. I'm not sure if this was the right solution, now my intake makes a significant hissing sound as soon as I put the car in drive (yeah its an automatic... for now). "

^^^ from http://www.civic-eg.com/viewtopic.php?t=10

Scroll down that page to see pics of what I am talking about.

Incase anyone ever runs into this issue and needs to fix it heres a nice link on how to do it: http://www.d-series.org/forums/diy-f...manifolds.html

 

Exactly, I think the 96-98's Y8 do not like starting from cold, mine is the same way, I assume this was addressed in 99.

 

The aftermaket pcv valves hiss, and sounds like a bad pulley bearing. I had the same issue, purchased a aftermarket pcv valve from Oreillys and had this issue. Purchased a pcv valve from my local honda dealership and wala! No noise, FIXED. Pinch your hose and the noise will go away to confirm its the aftermarket pcv, then go get a honda pcv valve.