Faint metal rattle at WOT
#1
Faint metal rattle at WOT
Hey guys, long time lurker here. I've had my '08 for over a year now without any issues and a few weeks ago I started hearing a bit of an odd noise.
Now when I'm in neutral revving the engine there is never a noise, so I feel like there's nothing wrong with the engine itself. When I'm in gear, accelerating slowly there's no issue either.
When I punch it, let's say trying to merge onto the freeway, after about 3500-4000 RPM I hear a metal on metal rattle noise from under the car. It doesn't happen every time I go WOT either. It usually only happens in 2nd and 3rd gear (rarely am I WOT 4th gear over 4000 rpm anyway) and 1st gear is too short to notice any noise.
My roommate says it could be something to do with my shifter. He had a Camaro with a similar noise and he had to replace a piece of rubber separating two metal plates. I wasn't too sure, he was in a rush and said he would explain more later.
Anyway, anyone ever had this kind of noise? What does it make YOU think is wrong?
Now when I'm in neutral revving the engine there is never a noise, so I feel like there's nothing wrong with the engine itself. When I'm in gear, accelerating slowly there's no issue either.
When I punch it, let's say trying to merge onto the freeway, after about 3500-4000 RPM I hear a metal on metal rattle noise from under the car. It doesn't happen every time I go WOT either. It usually only happens in 2nd and 3rd gear (rarely am I WOT 4th gear over 4000 rpm anyway) and 1st gear is too short to notice any noise.
My roommate says it could be something to do with my shifter. He had a Camaro with a similar noise and he had to replace a piece of rubber separating two metal plates. I wasn't too sure, he was in a rush and said he would explain more later.
Anyway, anyone ever had this kind of noise? What does it make YOU think is wrong?
#2
It could be the shifter but it very well also could be something loose on the exhaust underneath. Maybe the clamps are off or the metal part is rubbing them at certain RPMs.
Exhaust rattles happen often and they can be hard to find.
I spent two months trying to find two horrible things with our 06GT we had.
A rattle underneath as well as HORRIBLE vibration under the dash that ended up being caused by the straight through pipes causing vibration all the way through it with my cams and long tubes added. The straight thoughs were just too much with that setup.
The rattle was caused by the clamps not lining up properly with the hangars that were on them and it hitting a metal part at certain speeds and RPMs.
Exactly what I posted yours could be at the first of my post.
This is a common rattle issue. Of course other parts could be loose on the exhaust causing it though.
Exhaust rattles happen often and they can be hard to find.
I spent two months trying to find two horrible things with our 06GT we had.
A rattle underneath as well as HORRIBLE vibration under the dash that ended up being caused by the straight through pipes causing vibration all the way through it with my cams and long tubes added. The straight thoughs were just too much with that setup.
The rattle was caused by the clamps not lining up properly with the hangars that were on them and it hitting a metal part at certain speeds and RPMs.
Exactly what I posted yours could be at the first of my post.
This is a common rattle issue. Of course other parts could be loose on the exhaust causing it though.
#4
Could also be pinging from the car not being able to pull the timing enough to avoid it with the agressive aftermarket tune.
This time of year with the heat, heatsoak and/or gas that is even slightly off ideal can create problems with an agressive tune. The PCM can only retard the timing so far when it senses pinging. I had that issue when it stated to heat up with my 91 Performance tune. Took the global timing down 1 degree and timing between 2000-4000 and 4000-8000 down by an additional 2 degrees each. No more ping ever!
P.S. the reason you hear it under load (getting onto the freeway) but not around town is that you arent' pushing the motor so there's still sufficent timing margine there for the PCM to do its job. At WOT (and also under heavy load) the margin is considerably smaller.
This time of year with the heat, heatsoak and/or gas that is even slightly off ideal can create problems with an agressive tune. The PCM can only retard the timing so far when it senses pinging. I had that issue when it stated to heat up with my 91 Performance tune. Took the global timing down 1 degree and timing between 2000-4000 and 4000-8000 down by an additional 2 degrees each. No more ping ever!
P.S. the reason you hear it under load (getting onto the freeway) but not around town is that you arent' pushing the motor so there's still sufficent timing margine there for the PCM to do its job. At WOT (and also under heavy load) the margin is considerably smaller.
Last edited by Derf00; 08-18-2011 at 01:53 PM.
#5
Derf00, I took your advice and reloaded my tune. I took 1 degree off global and 1 off 2-4000 and 2 off 4-8000 and at first glance it seems like things are fixed. I only got a chance to go WOT a couple times and I sensed when the noise would usually show up and it wasn't there. I can't be certain it's totally fixed because the noise isn't 100% consistent but I'll keep punching it for a few days and see if I can make it come back.
If that was the fix, then at least I know exactly what pinging sounds like now haha.
If that was the fix, then at least I know exactly what pinging sounds like now haha.
#6
I had three sources of rattles...
The heat shields for the cats - Bent them slightly by hand enough to stop contact with anything.
The rod for my MGW shifter had a loose clamp (my fault) and the rubber tubing that was on the rod inched up enough to allow rattling of the rod in its clamp. Quick fix.
Then my D/S muffler was hitting the rear hanger after the exhaust heated up enough to expand some - Had the hanger bent slightly to stop the contact.
Just put it up on ramps to get under the car and see if it's the shields and also try to shake the shifter and see if anything is loose. If not, then also do a full throttle run or two after driving for a bit to get the exhaust to really heat up and see how close your mufflers are to their hangers.
The heat shields for the cats - Bent them slightly by hand enough to stop contact with anything.
The rod for my MGW shifter had a loose clamp (my fault) and the rubber tubing that was on the rod inched up enough to allow rattling of the rod in its clamp. Quick fix.
Then my D/S muffler was hitting the rear hanger after the exhaust heated up enough to expand some - Had the hanger bent slightly to stop the contact.
Just put it up on ramps to get under the car and see if it's the shields and also try to shake the shifter and see if anything is loose. If not, then also do a full throttle run or two after driving for a bit to get the exhaust to really heat up and see how close your mufflers are to their hangers.
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