Author Topic: 2012 Acadia running pig rich  (Read 1406 times)


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2012 Acadia running pig rich
« on: December 13, 2017, 11:21:27 AM »
My wife's Acadia has developed an intermittent rough idle after startup when below 35 degrees. When idling it will blow black smoke out the exhaust and the traction control disables itself. Once it warms up and reaches a certain temperature (I have not been able to track the temperature very close yet) it calms down and runs normal.

The check engine light does not illuminate and there are no codes active or pending. Using Torque Pro I see the fuel trims are off. When running rough Bank 2 is at -5% (rich) and Bank 1 is at +2% (lean, but not by much).

When I changed the oil in it last weekend I noticed the coolant reservoir was empty and I noticed some condensation on the underside of the oil fill cap. There was no evidence of water contamination in the oil I drained.

Wife took the Acadia to the GM dealership we bought it from to have them investigate. My hope was they would recognize a quirk and suggest a repair. All we got from the service manager was, 'Black smoke is normal for a GMC, your car is fine.' According to the service receipt all they did was scan it for codes....

What should I start checking? It is a 2012 with 88k miles. This is the first GM vehicle I've ever worked on (with exception of my father's 68 Camaro). My GoogleFu isn't working to find common problems with GM cars except for AC and timing chain issues.

The service manager pissed me off with his comment. We've had this Acadia for 3 years and have never experienced these issues.


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Re: 2012 Acadia running pig rich
« Reply #1 on: December 13, 2017, 11:50:40 AM »
To be entirely honest, these engines are a head ache.

Is this what yours is doing?
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First, the coolant issue.

The 3.6 is known for a water pump shaft seal leak that allegedly occurs when the coolant level is low, and I distinctly remember these coming from the factory with low coolant levels - we had to top them off during prep. Don't know if that's where your coolant is going or not, probably worth your while to get a mirror and look down at the bottom of the water pump. It doesn't always leave drips on the ground, sometimes it evaporates before it has a chance to drip off.

Not sure the job is possible without the vehicle being on a hoist. Pretty sure you have to do it from underneath.

Then the rough idle and smoke.. here's one explanation I've read:
GM DSM looked at my Acadia along with the multiple strart up videos I compiled. Smoke on start was not something he had seen before. We started 3 new Acadias on the lot and they all smoked on start up. Each started with blue smoke turning to black over a 30-45 second period.

GM Quality Control states this is a normal condition for the 2010 and 11 Acadias tied to new EPA standard. On cold starts, fuel is sent to the catalytic converter to start a controlled burn to bring the catalytic converter to operating temp. quickly. The result of this is the discharge of blue and black smoke.

This seems legit to me, as I remember very clearly the Camaros, Traverses and Impalas with the 3.6 blowing smoke and running a bit rough for a little bit when we'd move the lot to plow snow on fuck ass cold days. Just one of the reasons the 3.6 has a bad rep.

Next, there's a known issue with the PCV system for the LLT and LFX motors, and that could be at least part of your black smoke issue. The Camaro guys have figured out a cure, allegedly.

« Last Edit: December 13, 2017, 11:51:36 AM by 00XJ »