Finicky Air intake - 2008 C6
Thread Starter
7th Gear
Joined: Mar 2015
Posts: 7
Likes: 2
From: Indiana
Finicky Air intake -Lean Codes 2008 C6
After several days troubleshooting, my lean condition is resolved!
I purchased my 08 close to a year ago. On my drive home from the dealership, the car set P0171,174 lean codes so I turned around and sent it back to the dealer. They had the car for a week and eventually said they found an intake vacuum leak. All good, so I thought. A few months later, I get the same codes set. This time, I purchased the Bluedriver scanner. Had to educate myself on fuel trims and how to interpret what I was seeing. What I found was my car was running lean on both banks between 18 and 23% LTFT. Not enough to reset the code every time but I knew I had a problem. Based on my data, I knew I was not dealing with a vacuum leak so I focused on my fuel system. Rented a fuel test kit and had a steady 62PSI. Cleaned my injectors with no improvement. I had to rule out the MAF. I thought this was the culprit because the Barometric pressure was making step changes that coincided with an increase in LTFT. After installing a new MAF the Bar press was steady but I was still seeing the same increase in LTFT as RPM and speed increased. I then stumbled on an old post from another owner of an 08 that talked about a gap between a panel located in front of the air inlet filter that can trigger P0171,174 codes. Sure enough I had a 1/2" gap. The cover actually hung down a bit and acted like a scoop drawing in air through the front grill. It was as easy as a $5 purchase of 2 new push type plastic retainers along with some industrial aluminum duct tape to cover the many holes on the front panel before the air intake filter. LTFT's are now within 6%. I have a feeling this car had been driving lean for a long time. If not for a scanner and the great info. people put up on these boards I would be pulling my hair out trying to figure this one out. Much Thanks to all those who post!!!
I purchased my 08 close to a year ago. On my drive home from the dealership, the car set P0171,174 lean codes so I turned around and sent it back to the dealer. They had the car for a week and eventually said they found an intake vacuum leak. All good, so I thought. A few months later, I get the same codes set. This time, I purchased the Bluedriver scanner. Had to educate myself on fuel trims and how to interpret what I was seeing. What I found was my car was running lean on both banks between 18 and 23% LTFT. Not enough to reset the code every time but I knew I had a problem. Based on my data, I knew I was not dealing with a vacuum leak so I focused on my fuel system. Rented a fuel test kit and had a steady 62PSI. Cleaned my injectors with no improvement. I had to rule out the MAF. I thought this was the culprit because the Barometric pressure was making step changes that coincided with an increase in LTFT. After installing a new MAF the Bar press was steady but I was still seeing the same increase in LTFT as RPM and speed increased. I then stumbled on an old post from another owner of an 08 that talked about a gap between a panel located in front of the air inlet filter that can trigger P0171,174 codes. Sure enough I had a 1/2" gap. The cover actually hung down a bit and acted like a scoop drawing in air through the front grill. It was as easy as a $5 purchase of 2 new push type plastic retainers along with some industrial aluminum duct tape to cover the many holes on the front panel before the air intake filter. LTFT's are now within 6%. I have a feeling this car had been driving lean for a long time. If not for a scanner and the great info. people put up on these boards I would be pulling my hair out trying to figure this one out. Much Thanks to all those who post!!!
Last edited by gvonn; Feb 27, 2016 at 09:49 PM.
Team Owner
Joined: Sep 2005
Posts: 20,352
Likes: 568
From: Ventura County, Calif
Good info, thanks for sharing. Similar, but different, stories have been reported before about that intake system. Glad you figured it out and now you're smarter as a result of the journey too. 
