When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
When it's idling or I am moving slowly I hear the most
irritating noise echoing in my exhaust. Sounds like someone
is dragging a slinky through a steel dryer duct in an empty
locker.
It goes away if I rev it up a little or accelerate. This is
especially irritating in drivethru's and parking garages.
Oh, it's a 1992 Firebird 305 TBI. Mostly stock and no cat.
I've been putting it off because I am moving to an inspection
state next month and will be doing headers, cats, and the whole
nine yards anyhow. (Hopefully the problem will go away)
Any ideas? I'm hoping it's a loose bracket or something equally
silly and not something serious in the engine.
Sounds as if we both have the same problem. I too have this viberating noise when I'm at an idle. Intermittant.. somedays it does it other days it doesn't. From what I can tell on mine it seems to be coming from the front of the engine. Yet if I grab hold of the tail pipe (when cold of course), it stops. Ummm .. I originally thought it was the heat shield on the cat, but it didn't seem to be that. another possibility is the heat shield above the muffler. But I doubt it when it sounds like it is in the front. So what ever it is, it could be the same thing on both our cars.
Could be rusty baffles in the muffler. I have had new exhausts do this where welds have broke free inside and rattled around for a bit until they stick to something with the inevitable corrosion.
Is it coming from the rear? I had this same problem after getting my 3 inch cat-back system put in.
Look by the rear passenger side tire underneath the car, the part of the exhaust that bends over the panhard bar(is it the panhard bar?) and goes to the muffler. My exhaust piping was resting on top of it causing it to rattle a lot. What I did was I went out and bought some heater hose at ace hardware with some hose clamps. I cut the hose and put it inbetween the panhard bar and the exhaust pipe and secured it with the hose clamps. It fixed it perfectly, no more rattles, and only cost a few bucks and 10 minutes to do.
It's coming from the front of the car?!?!?!? Could it be pulley bearings? That's kinda what mine sounded like when my tensioner pulley bearing went bad.
My grand prix does the same thing. When you get a chance jack the car up then fire it up. Get someone to hit the throttle for you and findout where it's coming from.
We have the same problem on our 92 TPI 305 Z.
It does it at idle, and yes embarresingly enough at redlights, drive-thru's, etc. Dad seems certain it's a bracket rattling, somewhere up front in the Y-pipe or near the manifolds. If anyone figures this out let us all know, gassing it up at stop lights to keep the rattling away draws the wrong kind of attention, like from crown vics with funny lights on top.
Just for FYI, i had a tapping sound coming from mine. Well, after retorqueing the rocker arms, it still tapped. So, i called my all so knowing brother and he said that i might have an exhaust leak coming from my headers. So, i tightened up the header bolts and it went away....like i said, just an FYI.
I kno exactly what u guys mean. Its the heat sheild. The bolts vibrated loose on mine and its REALLY annoying. Go back and check it out. I can guranttee thats what it is. Later
My car made a loud tin can rattling noise forever and I finally found what it was. It was the parking brake braket hittting the driveshaft. Every time the driveshaft spun it hit the fallen braket. So maybe you should get under the car and look above your drive shaft. If your parking brakes don't engage, that's proabably the problem. If you see a metal thing hitting it then you know your problem. My noise was exceptionaly bad because I had a missing keeper on my u joint. I feel so stupid now Oh wells at least I laugh my butt off.
I didn't read the whole post , but i have edelbrock tes headers and y pipe . I had a rattle from my engine compartment , i found the y pipe to be rubbing on the cross member .
Transmission: Stock rebuilt tranny with 2k stall and cooler.
Ive had problems with cats breaking up internally. Itll go away for a while only to return and sound awful at idle or part throttle pretty much as you described. Jack the car up and tap on the exhaust with the car off and see if its the cat/s, if it is youll hear the pieces move around easily. Just an idea.
Do you have a little value between your exhaust manifold and the exhaust pipe (heat rise value)? It is controlled by vacuum. Mine was worn and it rattled during idle. Disconnect the vacuum line and see if it corrects the problem
I have the same noise sometimes, and I have a header leak. I will be re-torquing the bolts next weekend, so if it goes away I will let you know. I never knew you had to retighten the headers every six months. They have been on there for a year now
I have the EXACT same problem as you....drive thru's suck...it sounds exactly like a slinky from my engine compartment. if I'm idling 5-600 it goes away..but around 8-10 its there... let me know what happened with yours because it's so damn annoying and I need to get it fixed.
You should also have a heat shield above the rear axle on the passenger side where the pipe goes over. Check that out and look everything in that area over closely. My 3" catback was making contact on the unibody above where the panhard bar connects on the passenger side. I also had metal-to-metal contact at the hanger on the I-pipe in front of the muffler. This just about drove me nuts until I figured out I had two separate rattles.
Also, don't be fooled by the location of the noise - rattles like these can migrate from one end of the car to the other.
Good Luck.
I had the exact same problem on my 91 Camaro Z28. It was the catalytic converters that wore out. What happens, is that when a car that runs rich, the biscuits inside the cat break apart due to the excess gas not being burned properly. Also, when its running lean, where more air and not enough gas is being burned in the combustion chamber the excess heat from the engine will cause the biscuits(honeycomb shape filter inside converter) to break apart as well causing an annoying rattle noise. But check what the other have said being sure everything is tightened properly and then use a rubber mallet or the side of your fist to pound on the cat and if you hear the rattle there is the problem. Hope this has helped.
Hi all, sorry for digging up an old thread, but it showed up on Google. I got the same exact issue- rattle at idle and low rpm. I noticed it rattled more when AC turned on, then went quiet again and repeat. So i turned AC off and drove around in peace for like half an hour. Came to a stop then heard coolant boiling. Went to look, radiator cap was leaking. I have never had coolant boil or any overheating issues at all. What the F did I do? I just turned off AC, but it seemed to have caused it.
In the attached photo Notice how the 2 connections from AC are disconnected and the hoses stuffed with bolts. What are these for? These are from the prev. owner who i lost contact. It's a 305 naturally aspirated 1989 firebird.
12-08-2002, 01:48 PM
.
Oh wells at least I laugh my butt off. 
