Odd vibration at high rpm

Unbreakable

Original poster
Member
Mar 6, 2016
6
Calumet, OK
Under acceleration, such as passing on the interstate, at around 4500 RPMS and higher, there's a vibration and I suspect that it's the catalytic converter since it tends to be somewhat sluggish during this acceleration. Does anyone else experience this? Is it pointing to a slowly plugging cat?
 

gmcman

Member
Dec 12, 2011
4,656
You would need to perform a backpressure test to confirm if the cat is restricted.

Does the vibration follow rpm or road speed? Will the vibration dissipate if you ease off the accelerator?

Could be U joints going bad, could be a torque converter, wheel balance, etc...hard to say.

How many miles and will it vibrate in 1st gear at 4500? Or only at higher road speeds?
 

Unbreakable

Original poster
Member
Mar 6, 2016
6
Calumet, OK
Vibration eases off when you let up on the foot-feed and goes away under normal driving conditions. I think that under hard acceleration either the heat shield on the cat is resonating or the flow of exhaust is being restricted. I've read where some have taken loose the front O2 sensor and test drove, but I'm not real wild about this.

I've not tried 1st gear up to 4500, I'll give it a go when I get off work tonight.

This is a 2005 GMC Envoy, 4.2 with 138,000 miles.
 

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