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Discussion Starter #1
Lately when I start my G8 on cold mornings it shutters and almost stalls. The colder the temp, the worse the shutter is but after about 10 to 20 seconds it goes back to a normal idle and runs fine. I had read it might be the IAT and MAF so I hooked my scanner up to it, the IAT stays at 32°F regardless of how long its been running. However another function on the scanner is power- up IAT, and that one will gradually go up as I drive and the engine heats up. I'm curious as to what the difference is between the IAT and power-up IAT, if my IAT is actually bad, and what would most likely be causing this issue. Also my fuel economy seems to be suffering.
 

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I think I might be looking at the coolant temp sensor readings.
 

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Yes
 

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Does it want to go into the cold start high idle? If not, the. It seems like it thinks it’s already warm when it’s cold. So the water temp sensor as mentioned seems logical
 

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Presuming the check engine light is not illuminated, has the car been scanned for pending codes?
 

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Yep

I'm unfamiliar with the IAT vs IAT Power Up, so I don't know what those readings should look like. Just sitting at 32 does sound wrong though.
 

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Discussion Starter #9
Does it want to go into the cold start high idle? If not, the. It seems like it thinks it’s already warm when it’s cold. So the water temp sensor as mentioned seems logical
Yeah it does rev up into the cold idle and then it drops down to regular idle and starts choking so that makes sense.
 

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Presuming the check engine light is not illuminated, has the car been scanned for pending codes?
So over the summer it would rarely throw the code P0430-catalyst sys efficiciency below threshold bank 2. But it hasnt dont that in a while. I haven't had a code for anything else.
 

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Discussion Starter #11
Update. I replaced MAF sensor last week and haven't had a single problem with it... well I just threw a P0521 code for oil pressure, but that's an entirely different issue now. Lol
 

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Good and bad, thanks for your update.
 

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Which brand of mass airflow sensor was used as a replacement? By the way, there are various threads on the forum regarding the notorious P0521 code.
 

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Discussion Starter #15
Which brand of mass airflow sensor was used as a replacement? By the way, there are various threads on the forum regarding the notorious P0521 code.
I believe it was carquest, I'm not entirely sure but I think that's what it was. The engine seems to run slightly better than before and gas mileage improved a bit as well, I'd recommend replacing it if it's the original and it's around the 140k range in mileage. And yeah I just bought a new engine oil pressure sensor today, nothing I'm data logging is showing anything concerning from what I read. I'm thinking (and hoping) the sensor is just beginning to fail and cuts out occasionally.
 

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Would be nice if the car came with a factory analog or digital oil pressure readout on the instrument cluster versus the low oil pressure warning light. Did you replace the oil pressure sensor filter as well?
 

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Discussion Starter #17
Seriously man, but yeah I bought the filter and the sensor. It'll go in tomorrow.
 
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