Shudders either when accelerating or when AC is turned on

2008 BUICK ENCLAVE
120,000 MILES • 3.6L • 2WD • AUTOMATIC
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CRG-KIJ@ROGERS COM
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I have the CX model. mileage on engine is 110,000 kms. When I first felt this shuddering I went and saw a friend who is a technician. He found oil in Auto throttle body and some in mass air flow sensor. He cleaned everything up and shuddering went away only to come back after three weeks. I again found some oil in both of the said items and cleaned them up but the shuddering stayed. I started the vehicle and unplugged the MAF sensor but the SUV still kept on running. Where is the problem? I do not have money to throw away. I need your help please.
Jul 31, 2018 at 1:56 PM
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ASEMASTER6371
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Good afternoon.

Is your check engine light on? If it is, can you give me the codes?

What kind of air filter do you have? Did you install an aftermarket filter? Need to see why the oil is in the intake system.

Roy

https://www.2carpros.com/articles/engine-surges
Jul 31, 2018 at 2:16 PM
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CRG-KIJ@ROGERS COM
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Please note that the engine was a used one with 110,000 kms on it. Actual tachometer reading is 265,000 kms. The air filter is an after market one, which has no oil residue in it. Could PCV breather valves be the problem?
Jul 31, 2018 at 3:25 PM
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ASEMASTER6371
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As long as it is not a K/N filter, you are good.

Yes, check the PCV valve and see if it is working correctly. If it is, then you may have bad piston rings in the motor allowing blow by into the intake system.

Roy
Jul 31, 2018 at 3:45 PM
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CRG-KIJ@ROGERS COM
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How do I check the PCV valves?
Jul 31, 2018 at 4:55 PM
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ASEMASTER6371
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Pull it up off the valve cover and see if there is good vacuum at the valve.

Roy
Jul 31, 2018 at 5:09 PM
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CRG-KIJ@ROGERS COM
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You are talking to someone who is not adept at these things. Please advise how to test the PCV valve as ?
Jul 31, 2018 at 6:30 PM
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ASEMASTER6371
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Maybe it would be better if you took it to someone who can check it for you.

I attached a picture for you to view of the location. Remove it while running and put your finger on the end and see if you feel vacuum.

Roy

Image (Click to enlarge)
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Aug 1, 2018 at 1:41 AM