P0101 and P0106 Codes

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SP543

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Hello,
My Yukon is idling terribly and seems to be running very rich, has black smoke out of the tailpipe and is getting awful fuel mileage. Used a scanner and it is throwing P0101 (MAF) and P0106 (MAP) codes along with a random misfire code, which I figure is related to the 2 previous codes. I replaced both the MAF and MAP and still have the issue, although it seems to be slightly better but still stumbles at idle and is running rich. Any thoughts on what to try next? Does the PCM take a bit of time to adjust to the new sensors or should the difference be immidiialtey noticeable? Its a circuit issue, so possibly a ground wire somewhere that grounds both sensors that needs to be looked at?

Thanks in advance for any ideas.
 

Rocket Man

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Have a look at your throttle body and see if it's really gummed up- it might need a good cleaning. Also might be an intake manifold leak.
 
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SP543

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I replaced the intake manifold gasket a few months ago. I'll pull the throttle body and will take a look.
 
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SP543

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Also, this all started shortly after the oil was changed at a shop, where they overfilled it by around 1 qt. Any issues/things to check that could be a direct cause of this that might narrow down my search?
 
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SP543

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Seems a little better but definitely still running rich. What other sensors, besides the MAP and MAF, communicate with the PCM to control the fuel trim?

The truck runs normally at a cold start, but once it warms up a bit after 20-30 seconds or so and comes down to 500rpm it'll start stumbling.
 
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SP543

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Figured I’d update this in case anyone is experiencing the same things. Turns out it is the o2 sensor, Bank 2 Sensor 1. Finally tried unplugging it and sure enough, the truck runs great now. Was getting 7.2 mpg, now averaging 16.3 which is by far the best mileage I’ve seen with this truck.
 

Rocket Man

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Figured I’d update this in case anyone is experiencing the same things. Turns out it is the o2 sensor, Bank 2 Sensor 1. Finally tried unplugging it and sure enough, the truck runs great now. Was getting 7.2 mpg, now averaging 16.3 which is by far the best mileage I’ve seen with this truck.
I forgot about the o2 sensors. Glad you figured it out!
 

BOOM_FIST

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Figured I’d update this in case anyone is experiencing the same things. Turns out it is the o2 sensor, Bank 2 Sensor 1. Finally tried unplugging it and sure enough, the truck runs great now. Was getting 7.2 mpg, now averaging 16.3 which is by far the best mileage I’ve seen with this truck.

When you say "unplugging it", are you literally just unplugging the connector to the o2 sensor? Wouldn't that throw the readings off and cause the CEL to come on? I'm just curious, because I don't want to keep throwing money at this via the guessing game and I want to figure this out ASAP.

I was going to say either o2 or clogged cats for you...I just popped a P0101 last night after towing my 6x10 utility trailer 1.5 hours and I need to pinpoint if it's the MAF, o2's, or cat's myself.

I left the truck running with the A/C on for my wife and kids while I loaded the trailer and after about 20 mins of it just sitting there my trans temp and coolant temp were higher than normal. Not in the red overheating, but higher than it should have been. Freaked me out for a second...then when I went to pull out on to a main road it felt really sluggish and underpowered for a minute until the truck cooled down some. So, with those symptoms I'm really leaning towards clogged cat's since I'm right under 200k miles on this ol'girl, but I might have to look at the o2's. My MAF wiring and connector are good and the sensor itself looks brand new, but I've cleaned it anyway.

Thanks for this update!
 
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