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Discussion Starter #1
Hello, I used to have a 06 Civic Ex sedan and the gas used to last me for up to three weeks. Unfortunately It was totaled because someone rear ended me. Now I have a 08 Civic Lx Sedan. I changed the engine air filter, got the throttle body cleaned, fuel injectors clean, spark plugs change, cleaned the mass air flow sensor, and I’m having no problems driving what so ever. Before I did all this the gas would last me a few days, now it’ll last me over a week.

Here’s the main thing. I’m hearing a loud hissing noise on the driver side engine bay. I think I may have a crack in the stock air intake, but I have no idea what to look for.
 

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Perhaps a vacuum hose is off, or something wasn't tightened down after the throttle body was cleaned? You will just have to keep looking/hearing for the leak while the engine is idling. Wear gloves, but if you run your hand around the area you think it is coming from, you can sometimes pinpoint it when the noise changes a little as your hand covers/deflects the noise.

I've also heard of people using a spray bottle with water to spray different areas to pinpoint the leak. Don't flood it, but just mist different areas. The noise will change when water fills the gap.

Good luck.
 

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Discussion Starter #3
Update, finally had the time to check the stock air intake from the point where the air gets sticker in all the way to the box. I hand touched it and spray water but nothing. Also, I noticed that my gas has been lasting. But I’m still hearing the hissing noise. It doesn’t change in pitch when the engine is raved, I just don’t know what to do now because I know it’s not normal for our cars to do that
 

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Still think it might be a hose off, or a hole in a hose/leaking joint. Sounds like a vacuum leak, and a small one wouldn't necessarily mess up your fuel mileage. Sometimes the air cleaner housing is hard to get seated back just right - could that be the issue? Maybe focus on the parts your removed when you cleaned the throttle body? (or did this exist before you did any work).

I guess just keep looking around. Maybe stand different locations and see if you can triangulate where the noise is coming from. I have an engine stethoscope that I have used to find locations for noise, but I've heard of people using a hose held up to their ear to do the same thing. You look kind of funny, but if it works - what the heck.

Another trick is to take a page-sized piece of cardboard and use it to "block" areas of the engine and see if the noise changes. And have a helper also to pinpoint.

Good luck...
 

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Discussion Starter #5
I took my car to good year and they couldn't find the problem. Told me I was missing a clump, but there's no clump where the top half of the box seats. I wish I was more experience with this to take it apart myself. I live in Florida...
 

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I assume you mean clamp on the air cleaner box.

I'd suggest you look up YouTube videos on replacing the air filter. You should be able to note what clamps they have in the video versus what you have. You should have 4 clamps. If that is the issue, then you should be able to push down the box in the area where the clamp is missing and the hiss should go away. This assumes the upper cover is attached right.

Perhaps the cover has not been replaced properly - it does take a little finesse to get everything lined up, but it isn't that hard. If the cover is not on correctly and leaking, then you are letting unfiltered air into the engine and you should get it fixed.

You can buy a new clip for maybe $5 at the dealer if that is the issue. Should be easy to replace.

Good luck.
 

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Discussion Starter #7
Update, I changed a few stock intake hoses and nothing has changed. The hissing sound is still there. Plus, P0171 came up twice. So I’m amusing it’s a vacuum leak somewhere. Any ideas what to check?
 

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Sounds like one of the lines are letting out air (air leak). I would double check the throttle body and make sure everything was put on tightly. I would check the vacuum lines again. If the problem persists, then I would go to the junkyard and get a salvaged air box unit. That should fix it for sure. I'm aiming for the air box replacement - it really does sound like it's leaking air from a crack.

P0171 HONDA - Fuel Injection System Too Lean Bank 1
 

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Discussion Starter #11
Alright, I’ll go to the junk yard within the next few days and lost what happens after. Replacing the air box isn’t too hard, it’s just that one damn screw that’s hard to get
 

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Discussion Starter #12
Update. Turns out it wasn’t my air box that had a crack. My brake booster was leaking and made that noise. Had it replaced for $375 and the sound is 100% gone. Kinda weird. I’m still learning about cars so didn’t know what a brake booster was.
 

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That part costs about $70 new. Sometimes it's worth having them find the issue, google it, do it yourself and save... Not for everyone but $300 buy's you some fun.
 

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Discussion Starter #14
Yeah I was gonna buy the part myself, but it was sold out at the usual sites I go to. So I just got it from my mechanic.
 
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