CharlieDee

First off hello everyone. New old guy to the forum. I have an 01 LX coupe I just picked up for a daily driver. It runs real good but has a very loud whistling sound when wide open that starts abruptly around 4000 and stops around 5000. Doesn't change in pitch, and I cannot duplicate it with no load on the engine. It is for sure intake related, though spraying throttle body cleaner at the obvious places where the intake bolts up has no effect. I am going to disconnect the brake booster tomorrow to eliminate that, and do some more spraying of the intake mounts bolts at the bottom also. I have no CEL and other than that it runs great. Thanks in advance for any insight into this.

ezone

Got video or recording so the rest of us can hear it?

Is the intake and filter and chamber all stock?
Air filter housing loose, lid not secured, has broken or stripped bolts?

Noise could be exhaust leaks, steel gasket whistles like a reed under a high load...

CharlieDee

I will get a video in the morning. Stock intake, SRI in place of the airbox that was in the trunk when purchased. The lid screws are all corroded into the inserts which have all broken loose. I did put it back on to eliminate the SRI as the cause and it still made the same sound. I just went to the corner store and with the windows down and no radio I can hear a faint whistling upon even light throttle. The engine was replaced before I got the car, and my experience with a plastic manifold on my Ford Interceptor makes me wonder if the manifold itself is cracked. Thanks for the reply.

ezone

CAI/SRI lets ALL the noises be heard!
Did you install the huge black chamber that sits on top of the transmission and snorkel that runs behind the battery?
If you do not have all parts of the original breather system installed, intact, and leak free, you can and will hear lots of noise originating from the throttle body and intake system.

If you are changing parts of the breather system and that alters the amount of noise, then it's coming through the throttle body through the breather system, and it's normal..


If your intake manifold was cracked open it would be a huge uncontrolled vacuum leak and you would have a high idle and surge complaint. These don't break as a general rule. In the last few years I've read this forum, I only remember one person posting about breaking their plastic intake and it was accidental.

CharlieDee

I will get a video. The noise is very loud, NOT normal at all. I did put all the parts back, the tubes, resonator and airbox. The sound level and tone are exactly the same with the SRI or the complete stock system.

CharlieDee

I went to get a video but in doing so realized the sound is in fact coming from the exhaust not the intake. I don't know how many old timers are here but the sound is exactly like the whistling exhaust a VW beetle used to have. Not sure where but it is certainly not intake related like I originally thought, it sounds to be emanating from the cat area. I do not know the history of the car except that it has a low mileage swapped in engine and it sat for around 3 years before I got it. I'll probably just toss a header on it when the exhaust does fall off.

ezone

Right?
Got snapping noises and exhaust odor while running, especially cold?
Got loose hardware or broken studs?

====

I'm that old.
My first car was a 63 Bug.
I owned a 67 Bug up until a couple years ago.

CharlieDee

I have noticed it is much more prominent when cold, the sound almost disappears completely when at operating temp which further points to the exhaust as the culprit. Other then the whistle the car is quiet as a mouse. No perceivable exhaust leaks, or any out of the ordinary sounds. Which in the case of a Honda IMO is very quiet. To me it runs good though slow, but I have no reference to base it's performance as far as power. It is my daily and at the moment only available ride, my Vic is getting a trans and my bike is a little hard to carry tools on. I'll have the trans done in a couple weeks and then I will get into the exhaust on this and maybe just replace the whole mess before it actually falls off on it's own, all you rust belt people know what I mean...

ezone

Check under it, you may be surprised.
Shields rot away, fasteners rust away, but the pipes and cans are stainless and can last a long time.

If you try to install a header, the manifold contains the catalytic converter so you get to deal with fault codes and stuff. Gas mileage can actually drop with cat codes.

CharlieDee

The one thing I did notice under a decent duration full throttle pull, such as getting on the freeway it really gets an odor of nasty converter stink. I have a suspicion the cat is not up to par, the car did sit for 3 years and has had an engine transplant. The pipes are in surprisingly good shape, though the muffler looks to have seen better days. If replaced I will go stock replacement. This a daily driver that I would rather spend a few bucks on suspension and handling rather then power. I love the fuel economy and if I want to go fast I have the other car for that and a dragbike for that real need for speed.

ezone

No fault codes though? If the cat were failing (efficiency) the PCM should set a code for it.

Raw exhaust smell coming in the vents would tell me the leak is between the head and the manifold. The gasket there is steel and could be the likely source of your noise.
Pull the shield off and check hardware and look for sooty spots--leak evidence?


I expect Converter stink would be like rotten eggs or maybe gunpowder, and can be normal (and expected) during certain driving conditions. If that's coming in, I could picture having trunk sealing issues or similar.

CharlieDee

It is a smell of the combo of rotten eggs and gunpowder, the typical smell of converter. I get it more with the windows open then through the vents. No CEL and I do know it works, I got one when the flow sensor on the intake pipe was disconnected while I was investigating. Cleared the code and all is well with the CEL. Really can't tell if it's sooty, the end plug on the head was leaking pretty good. I have replaced it but have not yet done a degreasing of the plant. The noise is more of a curiosity then a bother, but I need to know what it is. I spent 25 years as a chassis designer, strange actions in cars compel me to find out what is going on, I can't help it.

ezone

I'm a troubleshooter. I NEED to figure out answers too LOL



If you get this during hard accel and driving hard, it's just about expected due to running richer for power.
When someone (a tech) takes a car out and runs it hard then immediately returns to the shop, most of the guys can point out the aroma and correctly speculate how it got that way LOL
Some cars are worse about it than others, and the amount of sulfur in the gasoline has a lot to do with how much odor there is.

Point is, I wouldn't condemn a cat based on that smell alone.
The PCM is the final judge of catalytic converter efficiency in my (99.9% stock) world.

Once you are sure there are no exhaust leaks all the way to the tailpipe and you are still getting that smell inside the car, you may want to check for body leaks in the rear.....figure out where exhaust is getting sucked in from the rear of the car. Cancer holes? Trunk seal?
The rear of the car is a turbulent low pressure zone so exhaust can hang there, and open windows can pull air in from the rear of the car.

CharlieDee

It was tapped lightly on the back passenger side, enough to crack the tail light. The fascia doesn't just right either, I thing the sheetmetal where it mounts at the near the bottom corner of the decklid is pushed in a little and compromising the seal at the corner of said decklid.

NDNV

It is common to have a cracked exhaust manifold on these cars.

ezone

Cast manifolds crack, yes, but I don't think that's your issue because you say it squeals under load.
That makes me think it's the steel gasket making the noise because it isn't clamped tight.

I've not heard a cracked manifold make a squeal noise.

NDNV

I believe the description is a whistle sound.
Still check both: cracked exhaust manifold under the shield and a loose steel gasket for the exhaust manifold.

ezone

Sorry, whistle.