Bizarre Noise at mid RPM

[ChromoTech]

I got the my exhaust done from where the two manifold pipes meet at the bottom of the engine all the way back.

maybe that will make the manifolds run cooler with 2 1/2 in. pipe all the way back i took out the precat and sensor area and had to drill a hole in the pipe for the sensor to fit into.

Do you guys think that it runs cooler??? i also got the K&N air filter

[Mark]

Hey STATIKUZ,

 

Did you ever find out what was causing your problem?

 

I'm becoming 99% convinced that mine lies in my Cats.

I reckon that the honeycomb is just about buggered and it's vibrating at a certain resonating frequency. The cats are 8 years old, so if I'm wrong, I won't feel too bad about replacing them anyway.

 

If I'm wrong, then my next suspect is my exhaust manifolds.

 

I'm getting a sluggish "flat spot in the carbie" kind of feeling in the gas pedal when the rattle kicks in.

 

I'll let you know how I go. Otherwise I'm still open to suggestions.

 

Cheers

[Mark]

Local exhaust guy says my cats are fine.

I'm getting desperate...

:help:

[sw]

just in case anyone cares......

 

you dont want your exhaust running cooler

if the gases cool in your exhaust they will flow SLOWER = restricted flow

[TrailChaser]

I'm not sure if this is the same kinda noise, but my speedometer jumps around when I run between 30-35mph. I have no idea why it does this, but it seems to work great other than that. When it does it's little jumping around routine, it makes a wierd kind of buzzing noise...

 

This particular problem may have already been addressed somewhere on here. If so can someone link me to it? I did a search a while back and didn't find anything. The problem hasn't bothered me enough to say/write anything till now, since this seems kinda relative.

[dkpath96]

a wire coat hanger and pliers works well on heat shields too

Talk about quick fixes to stange noises:

 

I had a similar noise coming from my Pathfinder, sounded like paper in a fan.

It only happened at 1800 and 3600 RPM, which threw me for a loop for a bit.

I took a stainless steel 3.5 inch PVC pipe clamp to both of my exhaust guards,

and bingo, no more noise.

[nige]

yeah i used that when i used to drive a 91 miata. That car was stupid-easy to work on

[Mark]

Hey, dkpath96,

 

You said:

 

"I had a similar noise coming from my Pathfinder, sounded like paper in a fan.

It only happened at 1800 and 3600 RPM, which threw me for a loop for a bit.

I took a stainless steel 3.5 inch PVC pipe clamp to both of my exhaust guards,

and bingo, no more noise."

 

PLEASE...PLEASE,PLEASE,PLEASE,PLEASE,PLEASE,PLEASE,PLEASE

go into more detail. It sounds just like my prob (only I'm getting it at 1350 & 2200 RPM).

What do you mean by "stainless steel 3.5 inch PVC pipe clamp"?

and "exhaust guards"? (y'mean heat shields? If so: Where? etc etc...)

:help:

[dkpath96]

Hi Mark,

I found that the vibration was coming from my exhaust heat shield, located

under the driver's side, just back of the front tire. The heat shield is rusting

away (as you can see in the pic below) and it would vibrate against the

exhaust pipe. So I went to the hardware store and bought a stainless steel

pipe clamp (see the pic.) Any size from 3" to 4.5" will do. Just unthread it,

wrap it around the heat shields, and tighten it with a screwdriver. Just be

sure you let the vehicle cool completely! It gets hot there. That solved it.

You can also cut off the excess (which I haven't done yet) with a pair of

tin snips.

 

I only had to fix the driver's side shield... but the other side may need it soon

too...

 

BTW, does anyone out there see a problem with this quick fix, as in should

I look into replacing these heat shields any time soon??

-thanks!

[MatterHorn]

dude ... you REALLY need to resize that pic man ... server space doesn't come cheap ... just and FYI ...

[Mark]

dkpath96,

 

Thanks for the pic mate.

I already removed all my heat shielding, though.

Maybe the shielding around the manifolds?

The hunt continues...

[JonesyUSN]

my truck did i just ran a chemical through for carbon and it cleared it up a little.. also try using a higher octane fuel.. that helped mine as well.. but if it is a carbon buildup problem using a higher octane will build up carbon faster... but i would rather do the carbon clean kit once a month rather then use low octane and have it there all the time.. i didnt bother reading all the entries so sorry if im repeating someone.. also my engine made the noise at about 13-1400 till about 3200 its almost a knocking but not quite.. also is it worse or louder when going uphill.. if you have a manual just throw into 3rd.. and shift at a higher rpm.. after about a month or so of shifting at higher rpms it should spit out some of the carbon.. again sorry if i am repeating someone

[Mark]

YEEEEEEEEEEEEEEEEEEEEHAAAAAAAAAAAAAAAAAAAAAAAAWWWWWWWWWWWW

:cool2:

I found the rattle.

The exhaust dude said it was engine (I thought it was the exhaust)

The dyno guy said it was transmission pssd

The transmission fella said it was exhaust...

Finally went to ANOTHER exhaust dude and guess what:

The LH cat was vibrating against the crossmember at certain RPMs when the engine was torque'ing just so on it's mounts. :o

It took him 5 minutes to find, 5 minutes to fix and cost me 30 bucks.

After all that drama.

Of course I'm still gonna replace the factory exhaust with something better but now I can wait awhile.

[dkpath96]

Congrats on finding your noise! Bet you're enjoying a more peaceful and worry-free ride. :cool2: