Rough idle at 600-700 rpm's

2007 GMC ENVOY
251,000 MILES • 4.2L • 6 CYL • 2WD • AUTOMATIC
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JEDIDIAH543211
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when at 800-900 rpm idle is fine (put my foot on gas with other foot on brake to achieve smooth idle). problem seemed to first begin when I had a throttle body error
i cleaned the throttle body by removing the throttle body, but i did not disconnect the battery (you website says this may cause problems).
immediately after cleaning the throttle body my vibration problem increased
the vibration gets worst if i drive in a stop and go fashion (traveling in the city) for extended periods, like driving for UBER.
Dealer said that clutch fan was problem, replaced clutch fan with no change in vibration. Alternator is now overcharging, but the vibration was a long time before the alternator problem. This problem has become worst over time, 3 years.
Very experienced mechanics haven't been able to help me.
Help please!
Oct 23, 2019 at 12:08 PM
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ASEMASTER6371
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Good afternoon,

Are there or was there any codes set in the system? If there was, I need those codes.

My first thought is the EGR valve. If it gets carboned up, it will remain partially open causing it to run rough.

https://www.2carpros.com/articles/engine-surges

Roy
Oct 23, 2019 at 12:15 PM