I have a 2015 Yukon Denali with the 6.2 and the car seems to drive normal, however whenever the accelerator is really pushed at all its as if nothing happens at all. It is as if there is almost no horsepower. The engine does rev up high but slowly and seems to shift normally. I have an OB2 and the torque app and looks like fuel pressure is normal the throttle all seems normal the only thing that seems not normal is the HP reading. Im not sure if that is even accurate but the highest I got it to go was maybe 50 HP at 3500 RPM. Also the car has no codes at all and no check engine or anything out of the ordinary.
Loss of Horse-power with no codes
- Thread starter p1zaul
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Bigkevschopshop
Full Access Member
Almost sounds like limp mode but would illuminate a code for sure... Could be a sensor starting to fail, something like MAF sensor can do weird things, plugged air filter or exhaust can do it also. It makes me think that whatever is wrong is not long term enough for a CEL to throw, maybe a few more run and restarts would make it throw a code. I know a soft code would be present right now probably so if you hit a shop for a scan they may see something. To save money, I would start with the basics, check oil level, air filter, etc and go from there. Visual inspection of the electrical plugs etc, make sure they are plugged in etc.
Thanks I will check the air filter, appointments are booked weeks out and have been driving like this for two weeks now. It seems pretty dangerous as you can really not pull out in front of anyone it is so slow. Shop thinks possible catalytic converter is clogged. Not sure how I can tell.
How many miles on it? Has it ever used oil in between changes, and what is your oil change interval? Have you ever cleaned the throttle body? Also, did you get gas at a new station recently? Maybe some water in the fuel?
Edit: I would agree is sounds like plugged cats, but could very well be a MAF sensor as well. I had a flaky MAF sensor in my 2001 impala and when it acted up, it was a real pooch......sometimes couldn't get out of my own way.
Edit: I would agree is sounds like plugged cats, but could very well be a MAF sensor as well. I had a flaky MAF sensor in my 2001 impala and when it acted up, it was a real pooch......sometimes couldn't get out of my own way.
So it's got just offer 100k, I don't think it's burning any oil and I change every 5k full synthetic myself. Gas has been pretty much just Costco and I have recently added some techron. I took a look at the throttle looks good and also sprayed that aerosol sea foam in there. No difference at all in the last few weeks.
tooleyondeck
Full Access Member
I concur with the other members here, check your MAF and throttle body and give them a good cleaning. Keep us updated when you get it figured out. Hopefully it is something simple.
Bigkevschopshop
Full Access Member
Easy test for Mass airflow sensor, just get a cheap one from the local parts store and replace it, if it doesn't work take it back.
k_arnold72
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Have you done any modifications or tuning recently? Did you just wake up one morning, turn it on and it was acting up?
Update, I just took the car on the highway, at around 50mph I tried flooring it and all of a sudden the car woke up. Came to a stop and floored it off the line and it was totally back to normal? Is it possible or was the sensor but needed some time to reset?
Strange.
Water in the fuel?
ninjaplumber
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Is it possible timing is being retarded due to a low octane knock? Are you using premium fuel?
Update, brought car to a shop and after two days could not figure anything out. A week goes by still drives like it's towing a yacht without a trailer while I wait for an appointment at the transmission shop. The morning of my appointment the car is totally back to normal, I bring it in anyway and they see nothing wrong. Next day the problems back. Now I bring it to the dealer and they say it needs a new MAF sensor. I tell them I just put in two in the last few weeks but they say the delphi brand is no good needs to be OEM. Quote be almost 700 to change the sensor get them down to 300 and they change it. Car drives normal for half a day now the issue is back. Now they are saying it could be the harness connector to the sensor and want to splice in a new harness. Could that actually be it?
Solved, I purchased a new harness and installed a new air filter and even purchased a fourth MAF sensor and this all made zero difference. Called dealer and was told it must be the ECU and it would need to be replaced. While searching estimated cost or if possibly a diy I came across a thread about resetting the ECU. As a last ditch effort I followed these instructions and it actually worked. Car has been driving better than ever for past few days now
To reset the entire car computers disconnect the battery and place a resistor in between the positive and negative terminals of the car. Leave this for about 20 minutes and then hook the battery back up. Then turn the car on and let it sit for about 5 mins.
To reset the entire car computers disconnect the battery and place a resistor in between the positive and negative terminals of the car. Leave this for about 20 minutes and then hook the battery back up. Then turn the car on and let it sit for about 5 mins.
My wifes 2020 Tahoe had this same issue. I found the inline anti drone flap in the exhaust system had gotten sticky and was basically blocking the exhaust. I rigged it to stay open and now it runs normal. I plan to leave it for the week to see if it stays running normal and to see if there’s any annoying exhaust drone before I either fix it or cut it out of the system.
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