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Rattling Sound During Acceleration

USMC.Cpl

By USMC.Cpl
in Ask A GM Technician

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USMC.Cpl New Member

USMC.Cpl

Posted
Posted

Just bought my first silverado in July after i totaled my jeep (sad day). The truck runs great, done a few things to it however there is one problem i cant seem to pinpoint what it is. Anytime i drive or accelerate there is a sound coming from underneath the truck somewhere that sounds like a rock in a coke can. Anyone have any idea what it is??

Dnt Senior Enthusiast

Dnt

Posted
Posted

I would guess that the catalytic converter guts have come loose. Jack it up and hit the exhaust piping it will probably make the sound. I had a jeep do this and i cut off the catalytic converter split it into 2 pieces and hollowed it out the stuff is a white honeycomb materials looks like ceramic it will bust apart easily. But I have a mig welder to put it back together and on with that you may not have that luxury.

  • Like 1
geswek Enthusiast

geswek

Posted
Posted

I have the same noise and have for the last 24k miles--same shit--rock in coke can when I'm driving. It happens at different RPMS and loads. I can always make it happen when I am climbing a bridge or something with uphill grade.

Jsdirt Senior Enthusiast

Jsdirt

Posted
Posted

Thank you for your service, Corporal.

 

I agree with Darryl on this one - that was my first thought as well.

geswek Enthusiast

geswek

Posted
Posted

I'm run mine by exhaust shop -- I tried the hammer to cat trick and all I heard was a hammer hitting the cat. LMAO

 

Assume you need to actually use rubber mallet? (I don't have one.)

Jsdirt Senior Enthusiast

Jsdirt

Posted
Posted

You go hammering on a cat with a steel hammer, if you didn't have a rattle before, I can almost guarantee ... you will now! :noway:

  • Like 1
Trp234 Enthusiast

Trp234

Posted
Posted (edited)

What have you done to it? After headers and full exhaust I developed a rattle after several months. It was the flex pipe rattling on the frame under very low acceleration. Raised back up and all fixed.

Edited by Trp234
geswek Enthusiast

geswek

Posted
Posted

I don't want to get too excited yet -- I went and put 89 octane in my truck yesterday because someone said it might be pre-detonation. I tried EVERYTHING this morning--everything I know always reproduces it-- and could not get it to make the rattling sound again. It was 61F this morning so not sure if temperate plays role; going to check again today on my way home. I literally cannot get this dang thing to make any noises.

Jsdirt Senior Enthusiast

Jsdirt

Posted
Posted (edited)

I have to run premium in mine, because when I tow, the engine sounded like it was going to grenade from detonation. BAD!

 

Could very well be what you were hearing. I didn't even think in that direction - that's the trouble with internet diagnostics. :)

 

Is that a flex-fuel vehicle? Is that even an option anymore, or are they all flex now?

 

I believe my problem from day one has been an out-of-spec alcohol sensor. Always reads 18-24% alcohol content. On a full tank of ethanol-free fuel from NY, it still read 12% (filled up with fuel warning light on - it was empty). If the computer thinks you've got high levels of ethanol, it will not only increase fueling, but advance the ignition timing too - that's why the spark knock happens. The more ethanol it thinks is in there, the farther it will advance timing.

Edited by Jsdirt
geswek Enthusiast

geswek

Posted
Posted

I don't know if it's flex or not.

 

I just did another 40 minute ride on highway to an appointment. I had no success recreating the noise.

 

If this is it--I've been running with this for at least 15k miles LOL.

 

 

Sent from my iPhone using Tapatalk

Jsdirt Senior Enthusiast

Jsdirt

Posted
Posted

I let mine rattle away for over 40k miles before I started running premium. I just backed off the throttle when I heard it. Eventually, I got tired of backing off the throttle - I want to MOVE!

 

I need to actually get in there and fix the problem, though. My band-aid solution has cost me thousands of dollars in unnecessary fuel costs. These trucks should run on 87 - they're naturally aspirated, and have a reasonable compression ratio.

 

I'm still not 100% certain if this sensor is sold separately from the fuel pump assembly on my '07. Have lots of other things on my plate. I need to look into that ...

geswek Enthusiast

geswek

Posted
Posted

It's been a week and I have about quarter tank left of 89. I have no rattle anymore and my truck drives WAY better!

 

I'm going to contact Lew, he wrote my tune and I'm assuming something is wrong for it to do that on 87 octane.

 

 

Sent from my iPhone using Tapatalk

  • 3 years later...
Ybboobie New Member

Ybboobie

Posted
Posted (edited)

I know this is a super late reply I created an account just to make this comment I was recently having this same issue super confused on what it could be ended up being the starter i guess it wasn’t disengaging all the way and was causing my rattle I hope this helps someone out there ps (if your starter sometimes grinds it’s most likely the problem)

Edited by Ybboobie
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  • 1 year later...

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