Hi everyone,Im brand new to this site but have been searching the archives alot lately trying to find a solution to a problem Im having with my 92 Accord. The car runs great,but for about a year now it has a pretty loud suction noise that comes from the intake tube when I turn the car off.( only for about 2 seconds like a valve isn't holding vacuum) Ive tried to locate the cause of this noise but have had no luck. It is definately coming from the intake side because Ive had someone turn the car off for me and right after the engine shuts down the suction noise is very loud inside the air filter box. Also recently my coolant resivoir has been bubbling with pressurized air after a long drive! My first guess was a leaking head gasket.
So I replaced the head gasket,& had the valves redone.But Ive still got a suction noise on shutdown! According to the manual, the FITV will allow air to enter the cooling system if its leaking. I checked my FITV and it DOES leak after the car is warmed up,indicating that it is bad. But before I go replacing parts I would like some input. I relize there are a few valves on the intake side that might cause this issue. Is the air in the resivoir related to the suction noise? This car is just my backup car but it has become a personal mission of mine to fix the problems with it! Thanks for any input.

 

If you take off the intake tube and cover the port in the throttle body for the FITV, the idle should not change. There may be a slight suction on it.

I would clean both sides of the throttle plate and the bore of the throttle body with TB cleaner, a rag, and an old toothbrush; because some air should get past the throttle plate. If the crud that builds up seals the plate, it could cause the air to be drawn through the FITV, IAC, or the air boost valve that would make a noise?

Also check that the air filter is in good shape. Inspect the intake tube and box below the filter for any abandoned nests, etc.

 

Thanks PAhonda for the input! So I pulled the intake tube off and had the wife start the car and turn it off and I tried to locate the source of the suction noise. Its very noticeable with the intake tube removed. The throttle body housing and the butterfly flap are very clean. The suction noise is coming from inside the throttle body, behind the butterfly flap and only makes the noise after shutdown of the engine, every time,hot or cold,even if the engine is started for just a few seconds. Its a very strong,deep suction noise. Im thinking its got to be one of the valves(IAC,FITV, or boost valve) not closing or opening all the way. Witch port leads to the FITV?

 

There are two ports inside the TB. The upper one is for the IACV, the lower is for the FITV. The air boost valve has a hose that goes to the intake tube.

Are you having any idle problems?

You may also want to clean out the screen that goes to the IACV.

There is some info in the DIY section about FITV cleaning in the first part that has some information that will help.

 

Ok so today i went through all 3 valves (IACV, FITV, and the boost valve) cleaned them,inspected. I couldn't find anything obvious. I also checked the brake booster check valve,pcv,and any other vaccum line that goes to the intake. Im not having any idle issues at all. The car starts right up and idles down after it warms up just like its supossed to. But I cant help thinking that this suction noise that developed about a year ago, is causeing my air bubbles in the coolant resivoir,witch also started about a year ago! I think I will post a youtube video tomarrow so you guys can hear this noise. Maybe someone will recognize it. Any other suggestions? Im also gonna pressure test the coolant system.