Tahoe 2009 - Rough Idle when AC turns on.

Saanni

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Hi All
I have Tahoe 2009 LT 2WD. My truck has 281,000 miles on it. I purchased this truck 5 months ago.

Since 2 months I am trying to figure out the rough idle on it while AC is on only & rpm goes up and down from 500-700 with vibration(when vehicle slows down) from cabin or under the hood not sure. (it stop fluctuating when I turn off the ac)
I also noticed the vibration like buzzing sound at 68 mph----(110 km/h).
Someone just frightened me yesterday that this is due to weak engine & that's the reason before going to mechanic I wanna ask your opinion.

I also changed my spark plugs 2 months ago.

Regards
 

zora

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Do you have a check engine light on?
Did you have the problem before you changed the spark plugs?
Have you checked motor mounts?
Have you cleaned the throttle body?
Not knowing the maintenance history and having 281k miles there are many possibilities.
 

Saanni

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No check engine light.
The problem was not there before spark plugs change.
Motor mounts has been changed recently, but those were probably local market made as i am in Saudi Arabia, spare parts are available in multiple grades quality so those mounts were local made.
No, throttle body is not cleaned yet. I will try that.
 

zora

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What plugs did you use, manufacturer and number?
What gap did you set them to?
Did you change the plug wires?
 

zora

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What number AC Delco?
You always have to check the gap of the plugs before installing them.
If the problems started after changing the plugs and wires that is probably related to your current problem.
Did you accidentally disconnect or break a vacuum hose?
 

Saanni

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AC Delco Spark Plugs Part No: 41-985
AC Delco Plug Wires Part No: 9748RR
I can remember , the mechanic was struggling very hard at the time of removing old spark plugs and wires.
 
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