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Rough idle - 2014 Buick Regal GS
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Joey14
Novice
Dec 13, 2022, 11:05 AM
Post #1 of 22
(2624 views)
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Rough idle - 2014 Buick Regal GS
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2014 Buick Regal GS,2.0L LTG turbo engine,74K miles
Hello everyone !! I'm having a rough idle felt most when the car is in drive and pressing on the brake.
No check engine light, but at one time had a P0171-00 pending code which never came back.It takes about 5 seconds once its put in drive with the brake depressed to start feeling it get rough. When its in Park, you can barely feel it.
Other than the idle issues the car runs fine, normal gas mileage as well.I do my own maintenance on the car. Spark plugs were changed at 55K and I just cleaned the MAF. I looked for vacuum leaks visually and with spray but found nothing. This car has a separate mechanical vacuum pump. To eliminate the possibility of a vacuum leak from the brake booster, as a test I removed the vacuum line to the check valve and plugged it, but the problem was still there.
Long fuel trims do not look good. I took 2 videos of live data from my scan tool so you can get an idea what I have.
If there is any other live data that can help with this please tell me and I will post it.
Thank You !
https://youtu.be/QZWpnIFr5Xg
https://youtu.be/DVIxeFxxVuU
(This post was edited by Joey14 on Dec 13, 2022, 11:06 AM)
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Dec 13, 2022, 12:12 PM
Post #2 of 22
(2614 views)
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Re: Rough idle - 2014 Buick Regal GS
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Leading cause is a vacuum leak. Since picking on bank 1 and using the brake (almost all use vacuum) check that first hose to under/low spot of air/fuel intake is dedicated to vacuum boosters. Oils will swell that or booster itself - anything to do with it matters. Plug it off if you want and or also see if using brake matters in neutral?
Other strong clue is pedal is hard quickly when car shut down has a reserve for power assist in wait engine or not may be the issue area.
Hose, check valve at vacuum boosters (as equipped) if equipped that way could be other method - hydraulic off of PS pressure?
Other test is push pedal, car off for a while feel if brake pedal sinks more without any more pressure a clue it isn't holding if vacuum that won't show with normal sprays that change engine speed when you find something,
Tom
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Joey14
Novice
Dec 13, 2022, 12:39 PM
Post #3 of 22
(2607 views)
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Re: Rough idle - 2014 Buick Regal GS
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Hi ! Thanks for the reply.
I had already confirmed that the brake booster is not the cause of a vacuum leak by removing the vacuum line that goes to the brake booster check valve and capping the hose off.When I applied the brake in Drive I still had the same issue.
Putting it in neutral gave the same result as having it in park.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Dec 13, 2022, 1:07 PM
Post #4 of 22
(2598 views)
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Re: Rough idle - 2014 Buick Regal GS
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Good move! You are impressing me for DIY finding this!
Next and unknown to most is brand name "Brake-Kleen" is fire proof vs others. Test that on some paper in a safe place make sure it still is.
That can find vacuum leaks can stall an engine if found, VOILA!
Silly but not is test oil dipstick if it has one (some don't) should be a vacuum however small no pressure coming out there.
On with tests don't waste $$ yet rather zoom in on a good reason.
PCV anything. Oil cap - anything that seals vacuum just know engine inside is supposed to be a slight vacuum if not save the novel for now this low mile car shouldn't be worn out the common reason but don't rule that out over low miles - prove it.
Go thru a list of the maybe things and rule them out.
Other thing for last note for now is a vacuum ball should be somewhere to make vents work on dash. Those have a check valve too is a goose chase if/when found careful neck will bust off if you can should go woosh right at it. If not find out why it's leaking out of your checking area,
T
(PS) Most a DIY visited site so aiming for YOU low cost checking till over our heads for more..........at a site - isn't being there!
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Hammer Time
Ultimate Carjunky
/ Moderator
Dec 13, 2022, 2:04 PM
Post #5 of 22
(2591 views)
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Re: Rough idle - 2014 Buick Regal GS
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When you refer to rough idle, are you sure it's not a tired motor mount. That will transmit vibration through the car at idle and will feel like a rough idle.
I'm not saying this is your problem but I would at least eliminate it as a possibility. The easiest way is to have the car running at idle and use a floor jack with a block of wood under the oil pan and lift it just slightly, just enough to lift the weight off the mounts. If the vibration goes away, you have bad mounts.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Joey14
Novice
Dec 13, 2022, 4:30 PM
Post #6 of 22
(2585 views)
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Re: Rough idle - 2014 Buick Regal GS
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I did check the engine mounts for play, though considering the live data with bad fuel trims, I'm leaning towards a lean issue (no pun intended lol). Something new I noticed today. I was looking at the live data 5 minutes after a cold start (80° here in Florida) and while in closed loop the LTFT was 7 and the STFT was -7 and the car was smooth. I didn't touch a thing and just watch the live data staying steady for a good few minutes, then the fuel trims shot back up and the issue was back. When I get chance, I will do a test from open loop to closed loop and watch the live data to see if this happens again. Could be a sensor going rogue well after closed loop.
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Hammer Time
Ultimate Carjunky
/ Moderator
Dec 13, 2022, 4:38 PM
Post #7 of 22
(2581 views)
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Re: Rough idle - 2014 Buick Regal GS
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OK first, play is not what you are looking for in motor mounts. Over time they lose the ability to isolate and disperse engine vibration. They get compressed, not ripped.
I would also suggest you put the scanner away. You're reading way too much into the variations. That's the computer's job to make adjustments necessary to maintain the correct air/fuel ratio. Even if you had a vacuum leak, nothing is going to change in performance until the computer reaches it's adjusting limits.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Joey14
Novice
Dec 13, 2022, 5:24 PM
Post #8 of 22
(2573 views)
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Re: Rough idle - 2014 Buick Regal GS
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If it is the motor mount causing a vibration, would the issue always be there at idle ?
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Hammer Time
Ultimate Carjunky
/ Moderator
Dec 13, 2022, 5:43 PM
Post #9 of 22
(2567 views)
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Re: Rough idle - 2014 Buick Regal GS
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Not necessarily. It would vary with engine RPM, engine temp and outside temp.
It's a very easy thing to test for as I instructed earlier.
Just have someone sit in the car, put it in drive and hold the brake as you slightly lift the engine weight off the mounts. He will notice the difference right away if they are bad.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Dec 13, 2022, 6:05 PM
Post #10 of 22
(2557 views)
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Re: Rough idle - 2014 Buick Regal GS
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Two tangents here. IDK, not there watching you can watch motor mounts with a helper an brake stand engine in gear. Forward engine tilts one way, reverse the other would change the feel totally.
No codes for motor mounts - you have a code, left bank issue rule that out or find out why keep on testing it has a vacuum leak doing that hidden. Find it. Other is engine worn out or a part cracked you can't see - yet may never see it by eye?
Tom
Tom
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Joey14
Novice
Dec 13, 2022, 6:08 PM
Post #11 of 22
(2555 views)
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Re: Rough idle - 2014 Buick Regal GS
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Sounds good ! Definitely worth trying. I may have to use my car ramps, my car sits low in the front to get the jack with wood under there.
TY
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Dec 13, 2022, 6:21 PM
Post #13 of 22
(2545 views)
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Re: Rough idle - 2014 Buick Regal GS
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Side note: Ramps I'm thinking of are deadly. Just throw those out,
Tom
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Joey14
Novice
Dec 14, 2022, 4:55 AM
Post #14 of 22
(2522 views)
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Re: Rough idle - 2014 Buick Regal GS
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I only use the ramps to get the car in the air, then I use jack stands 
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Hammer Time
Ultimate Carjunky
/ Moderator
Dec 14, 2022, 6:53 AM
Post #15 of 22
(2503 views)
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Re: Rough idle - 2014 Buick Regal GS
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Make sure you don't jack it enough to damage the oil pan. Just enough to take SOME of the weight off the mounts.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Dec 14, 2022, 7:28 AM
Post #16 of 22
(2493 views)
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Re: Rough idle - 2014 Buick Regal GS
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I have a real tear-arse reason to hate ramps.
1. They self crushed, I was able to escape!
2. Another time car rolled off, out a drive some luck of aleins it didn't hit anything and me bewildered under nothing with my tools in hands unharmed.
3. THERE WOULD BE NO THIRD!
***************
On lifting oil pans - Hammer is right - use soft wood as possible w no overlap to framing of car. That's AYOR stuff - B careful,
Tom
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Hammer Time
Ultimate Carjunky
/ Moderator
Dec 21, 2022, 7:26 PM
Post #18 of 22
(2399 views)
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Re: Rough idle - 2014 Buick Regal GS
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The purpose of the motor mounts is to insulate the body from the engine vibrations. When they get old and hard they stop doing their job.
If you had a lean condition to that extreme or a misfire it would set codes.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
(This post was edited by Hammer Time on Dec 21, 2022, 7:26 PM)
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Joey14
Novice
Dec 21, 2022, 8:10 PM
Post #19 of 22
(2389 views)
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Re: Rough idle - 2014 Buick Regal GS
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Good to know, thx.
I have an extended warranty (Buick Protection Plan) and engine/transmission mounts are covered, hopefully that goes smooth LOL
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Hammer Time
Ultimate Carjunky
/ Moderator
Dec 21, 2022, 8:12 PM
Post #20 of 22
(2387 views)
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Re: Rough idle - 2014 Buick Regal GS
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Good luck, It's always a judgment call as to when they are bad enough to change.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Joey14
Novice
Feb 14, 2023, 7:32 PM
Post #21 of 22
(1927 views)
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Re: Rough idle - 2014 Buick Regal GS
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Just wanted to give an update on my issue.The dealer replaced 3 mounts today. 1 engine mount and 2 transmission mounts. So far so good, no more vibration.I didn't want to be one of those guys that never come back after getting help and you never find out the outcome LOL.
Thank you so much for the help
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Hammer Time
Ultimate Carjunky
/ Moderator
Feb 14, 2023, 7:39 PM
Post #22 of 22
(1923 views)
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Re: Rough idle - 2014 Buick Regal GS
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Yes, thank you for updating us.
I will close this now.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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