I have a rough idle that comes and goes often after the engine is fully warmed up?

Tiny
BVERANO23
  • MEMBER
  • 2013 BUICK VERANO
  • 2.4L
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 104,000 MILES
So, a couple weeks ago after cleaning out the PCV orifice in the intake manifold (was clogged since owning the car and is a common issue with this model) without fully removing the manifold and using a pick to clear out the hole, I experienced a rough idle as I took my first drive. I believe I sprayed down the throttle body and MAP sensor (crc electronic cleaner on the MAP, which looking back. Might have left some residue). I have a rough idle that comes and goes often after the engine is fully warmed up. On cold starts it seems to drive normally.

Previous to the first rough idle I would get a single P0172 code that would come and go on its own for a couple months. I figured it had to do with the clogged PCV orifice and oil catch can setup I have. After the first experience with the rough idle I soon got an additional code of P0300.

I then cleaned the MAF, MAP, Throttle Body, and checked for any Vacuum leaks but couldn't find any (sprayed carb cleaner everywhere with no noticeable idle change then tried water). I was due for spark plugs, so I went ahead and replaced all 4 with OEM and did an oil change with no change to the rough idle. Except one time I saw a P0303 code which went away and reverted back to the P0300.

Here are the following values from my scanner. The values from 1 number to another indicates that the value is constantly changing.

Cold (Not Running) SHRTFT1: -100 | LongFT1: -16.4 | ECT: 73.40 | MAP(inHG): 28.64 | TP%: 32.2 | IAT11: 86 | IAT12: 75.20

Cold (Park/Idle) LoadPCT: 28 to 33 | ECT: 104 | SHRTFT1: -5 to +3 | LongFT1: -5.5 | FP: 43 to 44 | MAP(inHG): 7 to 8 | RPM: 880 to 910 | TP%: 13.7 to 14.1 | MAF(lbs): 0.01 | SparkADV: 9 to 16 | O2S11: 0.05 to 0.8 | O2S12: 0.79 to 0.8 | FRP: 449 to 462 | EVAPPCT: 27.8 to 29 | FLI: 27.5 | EVAPVP: -0.57 | BARO: 28.94 | CATEMP11: 996.80 | VPWR: 12.51 | TP_R: 3.1 | IAT11: 87.80 | IAT12: 91.40

Hot (In Gear/Idle) LoadPCT: 32 to 33 | ECT: 199.40 | SHRTFT1: -4 to +1 | LongFT1: -18 | FP: 51 to 54 | MAP(inHG): 10.34 | RPM: 738 to 760 | TP%: 14.9 | MAF(lbs): 0.01 | SparkADV: 6.5 to 10 | O2S11: 0.02 to 0.8 | O2S12: 0.76 | FRP: 436 to 442 | EVAPPCT: 13.3 | FLI: 40.8 | EVAPVP: -0.06 | BARO: 28.94 | CATEMP11: 998.60 | VPWR: 13.82 | TP_R: 4.3 | IAT11: 120.20 | IAT12: 125.60

(--Freeze Frame On P0300--) LoadPCT: 26.7 | ECT: 197.60 | SHRTFT1: 0.0 | LongFT1: -48.4 | FP: 59.18 | MAP(inHG): 8.56 | RPM: 889 | TP%: 14.9 | MAF(lbs): 0.01 | SparkADV: 19.5 | O2S11: 0.19 | O2S12: 0.74 | FRP: 472.82 | EVAPPCT: 13.7 | FLI: 14.5 | EVAPVP: -0.20 | BARO: 29.23 | CATEMP11: 1126.40 | VPWR: 14.208 | TP_R: 4.7 | IAT11: 132.80 | IAT12: 134.60

Any Help Is Appreciated! Thank You!
Tuesday, June 6th, 2023 AT 9:26 PM

1 Reply

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 42,909 POSTS
Thanks for the detailed question, I appreciate it.

MAF (lbs): 0.01

This is the problem; this is way too low I would get a new MAF sensor because cleaning doesn't always work. Here are the instructions on how to change the sensor out which should fix the problem. Let us know what happens and please upload pictures or videos of the problem so we can see what's going on.

This guide can help as well:

https://www.2carpros.com/articles/troubleshooting-rough-idle-in-your-cars-engine-7-common-causes-and-how

Check out the images (below). Please let us know what happens.
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Wednesday, June 7th, 2023 AT 11:23 AM

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