P2177 lean code in cold weather?

Tiny
LANNIE MUGLESTON
  • MEMBER
  • 2013 MINI COUNTRYMAN
  • 1.6L
  • 4 CYL
  • 2WD
  • MANUAL
  • 50,000 MILES
I have a 2013 base Paceman with 80,000 km on it. Since it's gotten cold here, it's giving me a P2177, System Too Lean Off Idle Bank 1 code. It never did it in the summer or fall, and it only happens when it hits around -8 Celsius/18 Fahrenheit or lower. In no way is the car driving any different. This past spring, the MAF sensor, spark plugs, and thermostat were replaced. I had it in my local shop and it passed the smoke test and fuel pressure levels were good. My oil cap was not sealing well so I got a new one, thinking that might be an issue. Code still pops up. Any ideas from you guys?
Friday, December 23rd, 2022 AT 1:01 PM

3 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,101 POSTS
Hi Lennie,

The cold air is likely causing something to contract when it gets that cold or there could be an issue with the engine coolant temperature sensor (ECT). I realize fuel pressure is correct, but if the computer thinks it is warmer than it is, it will lean the fuel mixture.

Just for curiosity, if you clear the code, how long does it take to return in the cold weather?

Also, take a look at the pic below. It is a list of circuits controlled by the ECT.

Here is what I suggest. When the temperature is cold enough for this to happen, check for vacuum leaks.

Here is a link that explains how it's done:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

If you are unable to find any leaks, we need to check if the ECT is equal to or very close to the ambient temperature. That will need to be done when the engine is cold.

Let me know what you find or if you have questions,

Take care,

Joe
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Friday, December 23rd, 2022 AT 5:21 PM
Tiny
LANNIE MUGLESTON
  • MEMBER
  • 2 POSTS
Thank you for the information! I guess that's a couple other things I should have added. When it was cold, it sat in my garage which was somewhat cold as well for 3 days. When I started it, it gave a pending cylinder 3 misfire that went away. When the engine is cold, for the first 5 seconds or so, the rpms will jump quickly between 1,000-1,200 and then it will settle down and run even. And as for your question about the light recurring, when it's at the -25 mark outside, I'll reset the light in the morning and but evening or the next morning it will come back on. Any of this other information give you more insight?
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Friday, December 23rd, 2022 AT 5:48 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,101 POSTS
Hi,

The idle speed at first may indicate an engine vacuum leak. Start with the test I indicated above.

As far as a pending code, it is usually tied to an intermittent fault. In most cases, the PCM needs the fault to appear again to set an actual code. If it doesn't reappear, the light will turn off after a set number of warm-up cycles.

So, in this case, the misfire may have happened once and not again.

Let me know if that helps.

Joe
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Friday, December 23rd, 2022 AT 6:53 PM

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