Why is my check engine light on?

My Buick, a 2014 Verano 2.4L with 128,000 miles occasionally lights it's CEL when idling if it's warmed up.  The code is P0172 Front bank rich and the Google suggested a possible misfire.  I tossed in new plugs to rule them out but it tripped the light again this afternoon.  It runs fine on the highway, accelerates normal, what direction should I be looking?

See if you can get your hands on an actual Buick manual. It'll have full information on just what can trip that code. If the code has to do with a rich error, I'd be looking at fuel problems instead of plugs.

How are the coils and boots?

Have you changed fuel vendors recently?

Is there a car website for Buicks like Pelican Parts for Porsches or Miata.net for the Answer?

Yeah, did not think so.

In reply to Toebra :

It uses the same engine as used in other GM vehicles:

The Regal, Verano, Captiva, Equinox and Terrain

https://en.wikipedia.org/wiki/GM_Ecotec_engine#LEA

My guess? Carbon issues:

http://www.revbase.com/BBBMotor/TSb/DownloadPdf?id=181448

http://www.gminsidenews.com/forums/f53/direct-injection-carbon-issues-142873/

Lots of references via search on "GM LEA misfires"

didn't that engine have earlier issues with fuel related stuff?

Definitely a sticky injector at that mileage. Not uncommon on GM direct-injected engine. If you can find a dealership that sells Deposit Control Services/BG Products services, have them perform a BG Fuel Induction Service (they even make a gasoline direct injection-specific induction service). It's what our dealership sells, and I've cured many a misfire and fuel trim code on a GM 2.4L or 3.6L with their services.  

In reply to NickD :

That will be my next stop.  I found a place nearby that does it. Is this something I should be doing regularly?  I would like to get a few 100k more out of this.

Wally said:

In reply to NickD :

That will be my next stop.  I found a place nearby that does it. Is this something I should be doing regularly?  I would like to get a few 100k more out of this.

Even a can of 44k in the gas tank, one of the components of the BG flush nickd recommended may help. Full disclosure I work for a distributed of BG... it won’t hurt, and may actually help. 

Its freezing out and Buford wants to sooth you with the soft, warm glow of the CEL.

In reply to Appleseed :

How considerate 

In reply to Wally :

Our recommended interval for the services at work is about 50k miles.

I had the cleaning done and no light for a few weeks. Last night I got home and the the car dieseled for a few seconds and it had a check engine light after I restarted it this morning with the P0172 code again.  It ran fine all day but dieseled again when I got home.  A quick Google check suggests it could be the high pressure fuel pump but is light on details for testing and changing it.  Time to order a manual.

Dieseling really suggests there is unwanted fuel in a cylinder, and pretty much says two things.  You have a stuck or dribbling injector, and direct injection comes with a bunch of it's own issues.

In reply to Streetwiseguy :

From what I read the high pressure pump leaks into the oil and then the contaminated oil can ignite in the cylinders.  I should be able to smell gas in the oil except my sinuses are a mess.

Wally said:

In reply to Streetwiseguy :

From what I read the high pressure pump leaks into the oil and then the contaminated oil can ignite in the cylinders.  I should be able to smell gas in the oil except my sinuses are a mess.

I've not heard of a high pressure pump leaking fuel into the oil.  I have heard, and know of, fuel being pulled past the rings down into the sump.  If the DI spray starts to really degrade, the pattern that will minimize that flow goes away and more fuel gets on the cylinder walls and down into the oil.  Di engines all have more oil dilution than PFI motors.  Thankfully, oil has gotten so good that it's not a huge deal for the nominal increase. 

For the dieseling, I'm right with streetwiseguy, the injectors are leaking and somehow putting in enough fuel to keep the car running.  Which actually shows an additional problem- you have so many combustion deposits that are warm that they are capable of innighting the fuel.  And all of that is likely sourced to dribbling injectors...

Other than running a lot of cleanser through, including a good dose of E10-20, I'm not sure of a good way to clean all that out.

In reply to alfadriver :

What I was reading last night was that there’s some seal on the ecotecs that goes bad and starts leaking into the oil but bad injectors and carbon could very well be the issue too. I think I’m reaching the age where I complain about new fangled contraptions and want my carburetor back.

In reply to Wally :

Damned kids.  

alfadriver said:

In reply to Wally :

Damned kids.  

Messing with things I used to understand and now I don't so much understand anymore , get off my lawn

A quick update: the light and dieseling would come and go at random. I gave it to a mechanic friend to drive for a week and it ran perfectly. I started dumping in a can of injector cleaner every few tanks and have had no more problems since the end of June. 

">" />I just fixed the exact same problem on my neighbors 2011 Buick Regal with the 2.4.

The high pressure fuel pump for the GDI is causing your car to diesel.   The high pressure pump in mounted on the left front of the engine and takes about 20 min to replace.  probably will take you longer to find the required 10mm socket needed for the job.    You will also need a special tool to release one of the fuel lines. 

EDIT.. if you are looking at the engine, the fuel pump is on the right hand side of the cylinder head.  

I even have a picture...

In reply to Doc Brown :

Thank You, I’m going to pretend that it’s healed for now because I have no free time but I know that I’m going to have to fix something sooner or later. At 145k all it’s needed were some bodywork, plugs tires, and fluid changes. I still even have the factory brake pads on it. 

Also, when replacing the high-pressure fuel pump you are not supposed to reuse the hard line from the pump to the fuel rails. I've done it before, either due to them not being in stock or trying to save the customer a few bucks, or just straight up forgetting, and never had any issue.

Thank you, I’ll be sure to pick up a new line with the pump because lately everything I touch goes to hell.

I seem to have jinxed myself. The car runs fine but twice this morning as I left a red light the engine stalled. I have no check engine light and it starts right back up again but I really don’t need more headaches right now.