Lately I've noticed when I'm accelerating and I'm at a pretty low RPM there's a metallic rattling sound coming from my engine. It's not consistent like an exhuast leak, I've had an exhaust leak before and it doesn't sound like that, but it's more random. My parent's old Chevy van did the same thing. It doesn't really sound like anything is loose either. Any ideas what else could make a noise like this besides exhaust?

 

I seem to have the same problem.... at about 1100-1300 rpm while accelerating, there is a loud vibration coming from the front of the car. It only gets louder as I accelerate harder in this rpm range. I thought that it might be my exhaust vibrating, and I will find out next weekend when I install headers and y-pipe. I hope that someone else has had this problem and knows the solution, because it is annoying!!!

 

Sounds like detonation (like marbles rattling in a can or a diesel type sound).

 

Had a sound like this in my Jeep Wrangler, turned out to be worn out connecting rod bearings. Replace them and the noise went away. It only occured under accelaration.

 

Yeah, kinda sounds like marbles in a can. So what causes detonation? What should I look into?

I do have scan software for my car, but I forgot my laptop when I evacuated What should I look for with that?

 

SAME EXACT PROBLEM on my 97 SS. it's a 6 speed and always thought it was something in my clutch assembly or a throwout bearing. marbles in a can is the perfect description and only while accelerating till 2000 rpm. i would love to hear a fix for this!!!

 

Sounds like spark knock guys.. run better fuel and take it easy.. make sure its not actually knock

 

Detonation will seriously ****eup your motor, I would drive it for long like that. Things that can cause it...

Non proper cooling of the heads
Obviously very high engine temps
Low octane gas (i.e regular)
Serverly advanced timing

Bascially high compression and heat along w/ lower octane rating gas can cause detonation.

Our motors utilize a high compression ratio which is why it also uses a reverse flow cooling system to cool the heads to prevent detonation. And is also why our cars recommend 93 octane.

You could still be getting knock w/ 93, maby because of what I described above but I think it would be rare, unless you have a heavly modded motor.

 

Use some higher octane gas, if you have not been running premium.
If you have deleted or non-working EGR, that could add to the problem.

 

I always run 93 Octane gas, so I don't think gas is the problem, unless I got a bad tank. I still have my EGR system intaced and am not getting any DTC's from it. I was driving yesterday for 10+ hours in stop and go traffic and 100 degree heat (evacuating), my engine temp gauge went up to 235 degrees before the fans kicked on and dropped it back to 210.

 

WELL..... everything that has been suggested so far i have already taken care of.... i got a ECM tune for my car from MADz28.com so i ALWAYS fun 93 octane, my eng temp NEVER goes past 1/4 guage or about 180 degrees because of the tune, plus a 160 thermostat. and finally the tune also de-sensitized the knock sensor, and i'm pretty sure it was making this sound BEFORE i did the tune. i have aslo replaced plugs, wires, and coil.

the car doesnt run bad while making this sound it still has plenty of power even at 2000 rpm. it just sounds horrible. the only problem my car has now is stumble at high rpm which im pretty sure is a bad fuel pump. also my clutch is dead and needs to be replaced within the next few weeks. the car has been making this sound pretty much all summer with no sogns of getting better or worse.

 

probably a bearing then. M v6 mustang had a bad main bearing and when you would hold it at like 2k you could hear it rattle like marbles in a can. It would run for a while like that, but eventually something will break and serious damage will occur. Try putting some 10w-40 in w/ some nice thick oil stabilizer and see if it changes anything. If it quites it down some, then its definetly a bearing.

 

Maybe you got "evac" gas. The high temps would also aggravate any tendency to detonate. I bet it will go away after a tank or so of new gas and some cooler temps.


[it gets confusing when someone comes in and hijacks a thread ]

 

Desenitizing the knock sensor will make actual knock or audible knock worse. If its there that is.

 

check Oil consumption guys.. our first ls1 had a typical oil consumption issue.. this would make it ping audibly even with factory timing