2018 Yukon SLE Rough Idle/Pulsating idle

[Erikf555]

Hi,

I hope someone may know what is going on here because my shop couldn’t find any problem.

It has had a rough idle pretty much since I bought it with 20k miles. The idle also pulsates when starting even after I have driven it. At operating temperature when restarting the idle will pulsate from 1000RPM’s to about 1300RPM’s about 8 to 10 times before it settles down to normal idle RPM’s think 500RPM.

Clean K&N air filter and I cleaned the throttle body, still does it.

Anyone know what to check next?

I sincerely appreciate any advice!

 

[Erikf555]

Nobody??

 

[Fless]

Might check the Idle Air Control function on the throttle body.

 

[Erikf555]

Might check the Idle Air Control function on the throttle body.

Is that something that can be done in the driveway or is it a scanner/code thing that a shop has to do?

 

[CaptainMurray]

Driveway, take the air intake to the throttle body off and clean with throttle body cleaner or replace it for $40.

 

[koachdaddy]

You mentioned the purchase mileage but not current mileage.

I have read about motor mount replacements so you may want to verify that those are intact.

 

[hagar]

There is no idle control valve on a 2018, it just opens the throttle blade to adjust idle air. Assuming the tune is stock and someone didn't mess any settings up, it sounds like a textbook vacuum leak. When you first start the truck, it holds the throttle open a pre-set amount. If you have a vacuum leak, the extra air will make it idle high and surge like that after start ups, until the truck has time to gradually figure out the throttle opening and timing needed, to lower the rpms down to the commanded rpm setting in the computer. Should be easy to troubleshoot with a live data scanner. Things like the truck adding lots of fuel on the fuel trims, as well as commanded vs actual idle correction data will show the probability of a vacuum leak or not.