'08 Sierra Throttle Body Issues

Steve Harke · March 28, 2009

PLEASE HELP ANY ADVICE WOULD BE AWESOME!!!

One day I was just beetling along like normal then BAMM Check engine light came on. Now keep in mind I have 17000kms on it, BRAND NEW still. Couldnt quite figure out the problem so I used my programmer to retrieve the DTC's, it came up P0171 System too lean Bank 1 & P0174 System too lean Bank 2. So in a dash I googled the OBD-II trouble codes and came up with the assumption that my MAF sensor, or my Oxygen sensor were at fault. Went back to my truck and fired it up noticed that my idle revolutions were bouncing from 700 to 900rpms then started playing with the throttle response, noticed a terrible lag. When the engine did rev up my cold air pre-filter sock sucked right in while making a huge vacuum noise. The funny thing is then I noticed that my cold air tube actually came off, so my throttle body was just sucking in everything. Put it back on, noticed a slight difference in performance but the check engine light was still on. Very next day I had it sent into a dealership. They told me all they had to do was reset the computer because the engine was put into a different state. Thought all was well until I heard the loud vacuum noise again when I took my truck home. Its makes a noticably loud flute sound coming from the throttle body when it opens up during quick revs. Throttle response times are at norm, doesnt sputter/ misfire just noise, and its driving me crazy. Now there is no check engine light so I cant retrieve DTC's on my own, can anyone help me resolve this issue? Can it still be my MAF sensor which is telling my throttle body to work hard, or is it my throttle body. My truck is a 2008 GMC SIERRA SLT 4X4 5.3L LY5 VIN=J if its any help.

Mr. Smith · March 29, 2009

PLEASE HELP ANY ADVICE WOULD BE AWESOME!!!

One day I was just beetling along like normal then BAMM Check engine light came on. Now keep in mind I have 17000kms on it, BRAND NEW still. Couldnt quite figure out the problem so I used my programmer to retrieve the DTC's, it came up P0171 System too lean Bank 1 & P0174 System too lean Bank 2. So in a dash I googled the OBD-II trouble codes and came up with the assumption that my MAF sensor, or my Oxygen sensor were at fault. Went back to my truck and fired it up noticed that my idle revolutions were bouncing from 700 to 900rpms then started playing with the throttle response, noticed a terrible lag. When the engine did rev up my cold air pre-filter sock sucked right in while making a huge vacuum noise. The funny thing is then I noticed that my cold air tube actually came off, so my throttle body was just sucking in everything. Put it back on, noticed a slight difference in performance but the check engine light was still on. Very next day I had it sent into a dealership. They told me all they had to do was reset the computer because the engine was put into a different state. Thought all was well until I heard the loud vacuum noise again when I took my truck home. Its makes a noticably loud flute sound coming from the throttle body when it opens up during quick revs. Throttle response times are at norm, doesnt sputter/ misfire just noise, and its driving me crazy. Now there is no check engine light so I cant retrieve DTC's on my own, can anyone help me resolve this issue? Can it still be my MAF sensor which is telling my throttle body to work hard, or is it my throttle body. My truck is a 2008 GMC SIERRA SLT 4X4 5.3L LY5 VIN=J if its any help.

I bet it is the intake gasket leaking causing a vacuum leak. This is why you have the 171 & 174 codes.