I purchased my 2007 Tahoe LT with 110000 miles on it last Friday. Over the weekend, I filled the fuel up then made a 150 mile trip cruising at 70mph the entire way. I averaged 15mpg and felt a vibration in the gas pedal while in V4 mode. I also have a vibration in the steering wheel while sitting still in park(obviously), and neutral both idleing at 700rpms. When I shift into Drive and remain still, the rpms go down to 500 then flutters up to about 550. This is when i feel the vibration the worst. I was told by a certified GM mechanic that it is idleing 200 rpms too low and that the idle control sensor needed to be repaired, about $1800 worth. So on my drive back to the dealership(Carmax) this morning where I bought the Tahoe, about a 40 mile trip, I was late for my appointment and was alone so I reset my avg mpgs in the computer and then proceded to cruise at 85 the entire way. I average 18mpg!!!! WTF!! I have been searching on here for a dealer diagnosis on this issue but have not found one. My dealer told me that the vibration was normal and that the AFM was fine so nothing could be done. I found a GM bulletin about the issue and presented it to the dealer but no help there. Also, the still vibration, dealer tells me the spark plugs are causing the vibration and are going to replace them. I have read about installing aftermarket computer chips and having luck with improvement of gas mileage and also some that have had no luck going this way. Anyone have any answers or help with these issues? Thanks.

 

Welcome to the forum.

Spark plugs should be replaced at 100K or earlier.

 

I assumed that they had been replaced due to the fact that they were included in the 100 plus point inspection. Wondering what else was missed?

 

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I'm sorry to hear of the frustration with your Tahoe vehicle. There are several possible causes for the issue you've described. It may be due to a power steering hose, debris in the transmission mount or it may be ring and pinion related. These are just suggestions, they are not meant as a diagnosis.

I encourage you to take the advice of your certified technician. They are in the best position for diagnosing the problem after a physical inspection.

Please keep us posted.

If you have any additional questions, please feel free to contact me.

Louis
GM Customer Service

 

Just picked up my Tahoe. The dealer took it to a certified GM Dealership. They recognized the rough idle. Paperwork said it was hooked up to the computer to 'relearn idle' but no change noted. The vibration in V4, they gave me a GM bulletin #06-06-05-001C which recognizes a change in exhaust note. No mention of a vibration in the bulletin. Carmax told me the idle was fixed but nothing to do about the vibration in V4 mode. I understand all tahoes come with a little vibration in V4 mode so maybe mine is normal. All of my passengers noted the vibration too. I guess I will take it to a 3rd party dealer and see what they say. I did some more searching last night about rough idle. My 07 came from California so maybe the air/fuel mixture is throwing things off being in Alabama at 600 feet above sea level. Either way, I love my new Tahoe! So much nicer than my 2001 Tahoe!