Unexplaneable engine noise
 

I have a 2002 Honda civic coupe lx stick with 188500 miles. Recently i have been hearing a strange almost squealing noise that originates form my exhaust. I can also hear the noise slightly from the hood of the car but it for the most part comes through the exhaust. The sound only occurs when i have the gas peddle pushed about 3/4 of the way down to the ground. When i push it down closer to 1/2 the of the way to the floor the sound isn't present any longer. The gear i have the car in seem to be irrelevant however if the car is in neutral i can go through the full rpm range without hearing the sound. It isn't to loud and does not sound metallic, if any thing it sounds like it might be a form of vacuum leak. Important things to note are that the car has a aftermarket intake as well as full exhaust and 5-30 oil (was recommended to me because i live in fl and its hot,) however i don't believe that these are causing the sound. What could be causing this problem? How might i identify what the problem is? How might i fix it? How much well it cost? Is damage being done to the car? Thank you for your time and knowledge i do appreciate it.

Re: Unexplaneable engine noise
 

Kinda sounds like you described the exhaust leaking.

Have someone stuff a wadded up wet towel into the tailpipe (don't burn any fingers) and hold it tight to "cork up" the exhaust (forces any leaks to show up easier) and you slide around under the car checking for leak noises from the exhaust pipes, all the way from the engine bay to the tailpipe.

Re: Unexplaneable engine noise
 

I tried this without results, i put the car up on blocks and checked the whole exhaust system and didn't find anything. Any other ideas? I think the problem may be a vacuum leak somewhere, but I have no idea where.

Re: Unexplaneable engine noise
 

If you are talking about this happening at 3/4 throttle and greater, then it isn't an intake manifold vacuum leak (there is very little vacuum at half throttle, and near zero vacuum at wide open throttle). Vacuum leaks are most readily apparent at closed throttle.
You might be hearing something that has to do with air velocity though.


If you mash the gas pedal 3/4 or more beginning at a low RPM such as 1100, hold it at 3/4 all the way to 5000 or redline.....is the noise present throughout the entire RPM range, or is there only a certain RPM range the noise is present?





The other things I can think of might be rusted exhaust heat shields, belt noise..... I dunno, I can't hear a darn thing from here.

You can hear lots of noise through an aftermarket breather, have you reinstalled the factory air filter box and that huge empty chamber as a test yet?


The 5w30 oil won't cause your sound, but it is wrong for the engine. 5w20 is stamped on the oil cap for a reason.

Re: Unexplaneable engine noise
 

its your air intake