• If you currently own, previously owned or want to own an Avalanche, we welcome you to become a member today. Membership is FREE, register now!

2011 Avalanche 5.3 liter with intermittent codes and hard starting

MountainAvalanche

New Member
Joined
Feb 18, 2020
Messages
3
:help:New to the Chevy world and have been researching the two codes that keep pooping up. 5.3 liter with 274 kilometers on it. Very well maintained and meticulous records, truck runs fantastic when warmed up for a minute but intermittently I get hard starting with some smoke or just needs some gas pedal and she goes, once its running its fine, no ticking or rattles in the motor, its very quiet. I eventually get P0175 and P0172. Codes are cleared and then after a couple days come back, some times a week??  How can I diagnose this one? its random.
 
https://www.obd-codes.com/p0175

https://www.obd-codes.com/p0172

https://www.obd-codes.com/forums/viewtopic.php?t=9419

many possible reasons...
 
There isn't just one cause though... The links ygmn provided, just like you probably found with your research, shows several areas to check & eliminate as potential issues. Did you test the MAF sensor readings with a scan tool to see if it is operating as expected? Clean the MAF sensor and throttle body? Check all vacuum lines? Check fuel rail pressure? Check fuel injectors? Let us know which of these you've eliminated as issues, and how you tested them, and we might be able to help you further!

Edit: something like this is where I would start when considering time/money spent to check something off the list of potentialities https://www.youtube.com/watch?v=OwJHw5pcsZQ 

edit2: do you have aftermarket cold air intake or other relevant parts?

edit3: keep asking questions and giving info, lets get this fixed man! Good luck

edit4: i swear i'm going to quit... is your fuel consistent? Do you use e85 one fill up and 93 premium the next? Has the problem occurred over multiple tanks of fuel?

edit 5: i lied about quitting... get access to a good scan tool and check the 'Fuel Composition' which shows the level of alcohol(ethanol)  in the fuel, i've now read that some flex fuel vehicles (like ours) will read abnormally high ethanol content which throws a rich fueling condition. I think you're looking for a fuel composition somewhere around 9%. Higher numbers (unless you're using e85) is not good. There is a fuel composition reset procedure that should re calibrate this (only if you verify it is the issue), but i think it is only available on a GM Tech2.
 
Update! it was indeed the fuel trim. Swung by a friends shop, he figured that was the problem as well, went out with the fancy device and bingo! He said it was way out like 73%
 
Did he fix the fuel trim, and what was causing it? Do your o2 readings look better?
 
Found this thread as I also am having the same issue with the same running rich codes and composition out of wack. We have replaced the MAF and have taken it to the dealer to have them reset the fuel trim and reprogram the ECM. Took it to an Indy who did a smoke test and still we have no better solutions.
 
Found this thread as I also am having the same issue with the same running rich codes and composition out of wack. We have replaced the MAF and have taken it to the dealer to have them reset the fuel trim and reprogram the ECM. Took it to an Indy who did a smoke test and still we have no better solutions.
The new MAF, was it OEM or aftermarket?
Fuel pressure psi? Physical reading if you can.
Everything stock? Cold air intake or aftermarket exhaust, things like that?
 
Back
Top