Crazy rattle when revving
Thread Starter
Teching In
Joined: Jul 2007
Posts: 41
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From: Amsterdam,The Netherlands
Crazy rattle when revving It is a 1998 z28 auto,it eats beamers for lunch and dinner hahaha
Have driven it quite hard today and now a very loud rattle is back,I can hear it upon idle, but it rattles away loudly when I rev it a bit.
The rattle was there before,1500k ago or so, but not so loud,at that time had a look from underneat;
it turned out to be 'in' the exhaust;engine and transmission sounded ok.
Drove with the car for a couple of weeks and it went away !!
Now,under the hood ,all sounds ok,no rattles there,even when revving.
Driving is fine,no strange noises(cannot hear any rattles) or strange behaviour.
Start to think it is pieces of catalytic convertor or couple of loose bolts, but in the exhaust?Have not seen any check-engine lights at this point,could the cat go bad without any warining from the ses?
Anyone any suggestions???I am baffled it has 95K Kilometers(about 70K miles)want to keep it for another 50K at least.
Have driven it quite hard today and now a very loud rattle is back,I can hear it upon idle, but it rattles away loudly when I rev it a bit.
The rattle was there before,1500k ago or so, but not so loud,at that time had a look from underneat;
it turned out to be 'in' the exhaust;engine and transmission sounded ok.
Drove with the car for a couple of weeks and it went away !!
Now,under the hood ,all sounds ok,no rattles there,even when revving.
Driving is fine,no strange noises(cannot hear any rattles) or strange behaviour.
Start to think it is pieces of catalytic convertor or couple of loose bolts, but in the exhaust?Have not seen any check-engine lights at this point,could the cat go bad without any warining from the ses?
Anyone any suggestions???I am baffled it has 95K Kilometers(about 70K miles)want to keep it for another 50K at least.
Sounds like a bolt on the y pipe is backing loose and then pinching together after a while. no big issue just will have an exhaust leak in a bit. Mine did the exact same thing. I actually never fixed it cuz it never continuously did it just intermittent. I even had the small exhaust leak.
You say it's in the exhaust but do you know where, is it inside the muffler or in the cats?
I had an issue very similar to this. I ended up jacking the car up I and started lightly tapping on the exhaust with a rubber hammer. I started at the muffler and moved forward, tapping every foot or so on the exhaust. Turned out I had a loose O2 outer shell like eseibel67, but also had an exahust bolt work loose and the washer was rattling. If you have rattle associated with the exhaust and don't know where it is, this will find it fairly quickly.
I had an issue very similar to this. I ended up jacking the car up I and started lightly tapping on the exhaust with a rubber hammer. I started at the muffler and moved forward, tapping every foot or so on the exhaust. Turned out I had a loose O2 outer shell like eseibel67, but also had an exahust bolt work loose and the washer was rattling. If you have rattle associated with the exhaust and don't know where it is, this will find it fairly quickly.
Thread Starter
Teching In
Joined: Jul 2007
Posts: 41
Likes: 0
From: Amsterdam,The Netherlands
Cause found,cat gone... Got under the car today because rattle got much,much louder and sudden lack of power yesterday.
sometimes a rattle when revving, sometimes not;
anyway ,lack of power also audible when revving a little,no loose bolts,no vibration or loose covers on the lamba's found.
No errorcodes,no alarms.
Turns out that after some playing with the revs.carefully....
pieces of cat. flew out of the tailpipe; grey stone chuncks ,one as as big as a mars/nuts-mini bar litterly spread behind the car,inside the tailpipe all grey with dust...
Dang, that one big chunk was probably blocking my respiration,it rattled too loud in the flat part of the y-pipe.
Power is as good as back ,rattle is almost gone for now.
After some driving,accel.power not completely as was,but much better.
Still no codes thrown.
Guess, need to find some new cats before the motor-management starts complaining.
sometimes a rattle when revving, sometimes not;
anyway ,lack of power also audible when revving a little,no loose bolts,no vibration or loose covers on the lamba's found.
No errorcodes,no alarms.
Turns out that after some playing with the revs.carefully....
pieces of cat. flew out of the tailpipe; grey stone chuncks ,one as as big as a mars/nuts-mini bar litterly spread behind the car,inside the tailpipe all grey with dust...
Dang, that one big chunk was probably blocking my respiration,it rattled too loud in the flat part of the y-pipe.
Power is as good as back ,rattle is almost gone for now.
After some driving,accel.power not completely as was,but much better.
Still no codes thrown.
Guess, need to find some new cats before the motor-management starts complaining.
Last edited by marthyh; Oct 9, 2010 at 03:52 PM. Reason: redundant info
Glad you found it, sounds like that cat busted pretty good. Considering the cats aren't still clogged/restricting flow you shouldn't really be down on power. The SES light might come on, but that will be because the rear o2s (tattle tails) will report cat malfunction. Shouldn't affect performance though.
If you still have a rattle after the cats are replaced check the muffler. If you don't have a straight through muffler parts of the busted cats might get stuck in there.
If you still have a rattle after the cats are replaced check the muffler. If you don't have a straight through muffler parts of the busted cats might get stuck in there.
