92 Honda Accord Suction Noise:VIDEO
 

Here is the video showing the "Darth Vader" like noise that my Accord makes when turning off the engine. It has been doing this for about a year,and I have ignored it hoping the problem would expose itself. But lately some more issues have surfaced: Hard starting after its has been driven and then parked for a hour or so, and also air bubbles in the coolant resivoir causing it to overflow. I have replaced the head gasket,pressure checked the cooling system,and went over every other item that might cause these symptoms. Im hoping I can find the cause of this "Darth Vader" noise and it is related to my other problems. Thanks for any input, and enjoy the video!


http://www.youtube.com/watch?v=EnXgJtW8CDc

I'm guessing the air intake hose was removed to hear the sound better? Cooling system holds pressure, did you test the cap and make sure to remove all of the air from the cooling system, and both fans are working correct. Hard starting, would need to know if there is or isn't fuel or spark when it is giving troubles, I could guess at a lot of things. Are there any stored codes?

You have some large vacuum source making the noise.

Yes the intake tube was removed to try to pin point the noise. The cooling system holds pressure very well. I haven't checked the radiator cap. I think I will just replace it with a Honda OEM one this week. I checked my fuel pressure today and found that it is a little low (30psi) and it bleeds off after about 15 minutes. So now Im suspecting a leaking injector, bad regulator or fuel pump causing my hard starting. Im pretty sure there is spark, during the hard starting. It acts like its either flooded or starving for fuel. Im gonna test the regulator tonight as the manual says. Im still confused about the Darth Vader noise! Oops I forgot to add that there are no stored codes,and yes I think I removed all air from the cooling system. The car dose not run hot and both fans work.

UPDATE: so i just tested the fuel system pressure again.and everything looks good. Its 45psi with the car running and the regulator vacuum hose disconnected and capped off. When the vacuum hose is reconnected to the regulator, it drops down to 35 then rises to 45 when removed again. The pressure also holds tight at about 32psi for at least 30min after the car is shut off. According to the shop manual, this is all in spec and checks out ok. So now what?! Everytime I think Im getting close to diagnoseing the prob, Im wrong. Ill test it again tomarrow after a drive. Would a bad or leaking IAC valve cause my symptoms and the suction noise?

Try plugging the lower port for the FITV on the inside of the throttle body with your finger. Turn off the engine. Let us know if the noise goes away.

If you cover both ports, the car should stall out.

Thanks for the input PAHonda! I think Im getting closer now. I started the car and covered the lower port like you said and the idle dropped alot but the car kept running. With the lower port covered and the car turned off the suction noise is still there. So I tried the same thing on the upper port only this time the suction noise goes away!:) That is the port for the IACV correct? Does that mean I should replace the IACV?

You can drain the coolant, remove the IACV and try to clean it out with some TB cleaner. There is a screen that may be clogged up. The two coolant connections could be clogged up that run into it and you may want to clean them out with a pipe cleaner.

Also check that the yel/blk wire has 12V when the key is in the II position to a ground bolt on the valve cover.

If cleaning doesn't work, then I would replace the IACV.

I think I will go ahead and just buy a used one from Ebay. I saw a few of them for around $35. I cleaned mine last week when I was going through all of the valves. I will check to make sure it has power to the yellow/blk wire. Im just glad I might have found the cause of my problems, at least one of my problems! Thanks for all the input:D

So after alot of troubleshooting and alot of help from everyone on this forum, I feel Im making progress. I noticed that my IAC makes a humming noise when the key is in the #2 position. I figured thats part of my problem and its locked up or shorted out. So yesterday I bought a used one from a Honda junk yard in town. If I plug it into my harness and turn the key to the #2 position, it also makes the same humming noise! Is that normal or do I have two bad IACs?