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Discussion Starter #1
My 13 ltz is having a rough idle when when in gear at a stop sign. I read through and found it could be the valve is clogged or the throttle body could need cleaning.I could not find a detailed “how to” so here you go!

I always disconnect my battery before doing anything (except filling washer fluid ?) then use a t30 hex to remove the plastic cover on top of engine . C93947D5-114E-4BF2-8982-616B803A728D.jpeg 3 screws

Now here are your pcv valves
912ACAB8-AC00-4379-A050-369DB9670E08.jpeg
The fun part...?
disconnect these ⤵ B506D299-2E8F-4409-82D7-0D47DAD06EE2.jpeg
DE9AD4A6-A4D3-4CB1-864A-423FCA53ED34.jpeg You have to press back on that little clip sticking up and slide to the left to open it. Once open you can slide it off by pushing towards the fire wall. I held it open until I removed it.
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Once the clips are removed you will need a 10mm socket to remove each valve.
67743


Btw- the air box can be removed if You need more space after you disconnect the clips holding the valves in.
67744

It’s held on with one 10mm bolt on the top right side. Obviously you will take off the intake tube as well. Also you will have to loosen the clamp holding the rubber for throttle body.
once valves are removed you can replace
With new or clean and put back in. Mine were free-meaning once I shook them, I was able to hear them moving around in the inside. I spray cleaned with throttle body cleaner on each end and let air dry for 15-20mins. I reinstalled the valves and put everything back. Hopefully this fixed my problem....I’ll find out after a few days. Fingers crossed
67745
While your at it you might as well clean your throttle body. If your going to remove that air box/baffle anyway. Remember to spray a Rag and wipe clean do not spray anything directly in to your throttle body. Hope this helps. I have a few more to post but let’s see!
 

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2017 SS Sedan 6.2L
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Did replacing the PCV valves help your issue? Usually when the 2.5L and other direct injection engines are running rough, the suggestion is that the intake valves (rather than PCV valves) and ports are clogged/dirty from carbon build up.
 
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Discussion Starter #3
Thanks cp, not that I have noticed ?‍♂. as of today when in drive (Stopped) the rpm’s drop a little.....and it’s not a big deal. More so an annoyance it’s probably 50-100 rpm lower than it should be and it makes her vibrate a little. Maybe the throttle body is still dirty? I did not want to mess up the motor and force the plate open to throughly clean it. Thanks for the suggestion! I will look into what you said ?
 

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If the car is off, you can push the throttle body open no problem. That's the only way to properly clean it. However, my guess is you have some carbon build up in the engine after 5-6 years and however many miles.
 
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Discussion Starter #5
My apologies mileage 99640. My concern obviously would be using sea foam/ b12 etc through the intake. But obviously that is the only way.
 

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No need to apologize! I appreciate that you've been active contributing to the forum, we need more folks like you joining instead of complainers. ;)

I would love to see your ports and valves scoped to see what they look like after all that mileage and time. You might need an all out wallnut shell blasting procedure to get everything like new again.
 

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Discussion Starter #7
Thank you! I’ll definitely keep you (all) posted and when I pull plugs I’ll post pics of what the inside looks like ?
 
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If the PCV are rattling that just means they aren't gunked up and stuck. The PCV valve is just that, it's a air metering valve that controls how much air is let into the engine at idle. Too much air or not enough will cause the ECM to try and compensate due to unregulated air entering the system. Dirty throttle body also affects that balanced air entering the engine. The pintle valve and orfice in the PCV will wear over time and just blowing carb. cleaner through them like we did years ago just isn't the cure today. Some engines just use a metering orfice instead of a valve that can get plugged. The old Sables I've had in the past were very sensitive to the PCV being worn, they would raise the idle 100-150 rpm erratically.
I'd first do a through cleaning of the throttle body like CP said and go from there before swapping out the PCV. TB dirty is a common thing on any FI vehicle. I'd make sure nothing's loose like TB mounts, intake manifold, etc. along with the usual vacuum line inspections if cleaning the TB and changing the PCV doesn't work.
Of course your ready for plugs at 99k, use only AC plugs.
 

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Discussion Starter #9
Thanks repairman, I actually changed my plugs out at 60k. I know I know.....I just can not see leaving plugs in for more than that. I believe that’s when you run into gapping issues etc. I used ngk plugs , you the senior members (no pun intended) know best so I’ll make sure to swap out for ac plugs. Thanks again for your help!

Thanks repairman, I actually changed my plugs out at 60k. I know I know.....I just can not see leaving plugs in for more than that. I believe that’s when you run into gapping issues etc. I used ngk plugs , you the senior members (no pun intended) know best so I’ll make sure to swap out for ac plugs. Thanks again for your help!
Also I’ll check all the items you listed, it can’t hurt right.
 

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I tried a set of NGK in my 5.3 Tahoe as I've used them for years in my snowmobiles. It didn't have a smooth idle like the AC's I pulled out at 80k miles. I put AC back in and idle was smoother. The NGK didn't miss fire and power was normal but the idle just wasn't as smooth.
 
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Discussion Starter #11
Hmm Maybe its one of the ngk's that are acting up. Well lets save money and try the basics. The vacuum line I wonder about...... for the simple fact as I said in drive stopped at a light. I get a ruff idle but in neutral or park nice and smooth.
 

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Discussion Starter #12
Just an update, still have the rough idle. Re cleaning throttle body did not help unfortunately. I will keep you posted on what it ultimately is.
 

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hey everyone silly question but can not hurt to ask, Should I be able to blow through either side of the pcv valve or should it be air passing through one way only? Cp and Repairman I also pulled plugs they looked carbon fouled. please let me know if I should start a new thread. I have pics of the plugs
 

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This is what carbon build up looks like in a direct-injection engine. That's why it requires special top engine cleaning treatments to maintain. You can't know for sure how bad it is unless you get a scope down the intake port to take a look.

 
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Discussion Starter #15
Thanks cp!! I actually did the seafoam spray through intake. I’ll order a scope and take a look. After I did the treatment, the problem is not so much a constant. She idles fine for a while when stopped at a light then at the next stop or red light it drops idle again. I agree with what you said “requires top end engine treatments to maintain” thanks again. I’ll keep you posted. I don’t want to be that guy to disappear and pop back up a year later lol.
 

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Thanks cp!! I actually did the seafoam spray through intake. I’ll order a scope and take a look. After I did the treatment, the problem is not so much a constant. She idles fine for a while when stopped at a light then at the next stop or red light it drops idle again. I agree with what you said “requires top end engine treatments to maintain” thanks again. I’ll keep you posted. I don’t want to be that guy to disappear and pop back up a year later lol.
@LiNy
Did you ever get the rough idle figured out?


Sent from my iPhone using Tapatalk
 

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Discussion Starter #17
@LiNy
Did you ever get the rough idle figured out?


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Hey vog unfortunately no....still no codes popped up. I’m actually taking to dealer just to get it checked on the 15th so I will hopefully have an update. Fingers crossed it’s just all in my head and the rough idle is actually just a vibration from a worn mount.
 
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Discussion Starter #18
After cleaning the pcv valves and the issue not being resolved, I ended Up replacing them anyway due to how inexpensive they are but Problem still present. I ran a code reader nothing found. In addition I ran an additional can of sea foam through the throttle body, problem still present ( Thank you Sr members for the suggestions). Brought to dealer today at 7am they had her all day . Called for an update at 5pm the service manager said they can not find anything wrong.....they also put a scan tool with nothing found. So I’ll be picking her up in the morning. Another can of sea foam can’t hurt. But Thank you everyone who replied.
 
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Two thoughts I'm having right now:
  1. Has anyone been able to actually see the condition of the intake valves?
  2. Do you know if the oil is the right viscosity and not over-filled?
 

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Discussion Starter #20
Two thoughts I'm having right now:
  1. Has anyone been able to actually see the condition of the intake valves?
  2. Do you know if the oil is the right viscosity and not over-filled?
I doubt they even checked. I’ll post a pic of the tech notes. The oil I check weekly if not every 3-4 days. I do a lot of city driving and in traffic for up to 2 hrs at times so I like to make sure all is well. Oil/coolant/brake fluid. Regarding the valves as we spoke on before, I am positive they are covered in carbon. My first can of intake cleaner through TB was not done till 100k. The problem came about right b4 100k.
 
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