I've made this post to another forum, and will paste my 4-5 posts here. Any help will be greatly appreciated.

I just bought a brand new Tahoe 2008 - When I'm in idle (Park/Braked/Or moving under 3 mph) - The engine block shakes and causes the entire Tahoe to shake. You can feel it sitting in the car. It's somewhat subtle usually, but at other times it's very noticeable. I took it back to the dealership - they ran tests, hooked up their computer, and said nothing is wrong with it. Told me to drive it for a few weeks and if it still does this to bring it back.

When I got home, I opened the hood and you can literally see the engine block shake every few seconds sometimes heavier shakes than others, and clearly this is what is causing the car to shake. Does anybody have a solution for this? Or understand why a brand new 2008 tahoe would do this? Please help. I'm also not happy that the dealership did not acknowledge the problem. If the problem remains, they're going to have to deal with a very loud and unhappy customer.

----


Also,
Got in it today and noticed at 2-3000 rpm, the car still shakes. So it's not just in idle. Hope they figure this out, cause I like my Tahoe, it's got exactly what I wanted in features and looks, too bad the engine runs like crap.
One more thing - When I drove their demo , seemed much quicker in acceleration than mine. Both Tahoe's had the same engine, could this also be correlated to the fuel injection?

Klydel[/align][/align]-----[/align][/align]
[hr]

Thanks for all the advice, checked the spark plugs, seemed all snug and in place. I'm taking it back tomorrow (Monday) and telling them they have to fix this and won't accept it until they do. It bothers me because last time I was there they said they don't even feel it, which is just a lie. This seems like a good dealership too, that is why we dealt with them and why I am so surpised by this.

I'll be sure to use the following...
- Lemon Law - they have to fix it or replace the car
- Complain until they fix it.
- Check the injectors
- check individual pulse widths and the duty cycles on each injector with flow benches.[/align][/align]-----[/align][/align]
Well I dropped off the Tahoe last Thursday. The Service Tech said that if it's some kind of fuel injection issue, then they wouldn't be able to fix it. That the fuel injector is balanced by the intake and emission sensors (something like that), and that the computer on the car controls the balance of the pistons/injectors, etc. But that he would check it out by running tests. Also, he said it might help by repositioning the motor mounts just slightly to see if this helps.

Saturday, they called and said your car is fixed and ready to go! My response was, "It's fixed?". They said, "Yap, fixed and ready". I was very cautious that everything was better.

We went to get it, and of course, neither of the service tech's were in on Saturday, so I had nobody to talk to. I read the paperwork of what they did, and basically the repositioned the motor mounts slightly, and that's it. Didn't say anything about running tests.

The car still shakes, and worse of all, I think it shakes more!

I'm taking it to my personal mechanic on Monday to get his opinion. He's actually someone that I trust. Then it goes back to the dealership. If they can't fix this problem, then it sounds like I got a LEMON.

Please give me feedback, you guys are helping me tremendously.

Klydel[/align][/align][/align][/align][/align][/align]

 

Klydel, please search the forum for "rough idle". We have many posts addressing this issue. I have a 07 LS 4.8 with the same issue. I did go to dealer and tested other Tahoes. They also had rough idle. One was even worst than mine. Again please search this forum. You will find many good feedback from bright folks here.

 

Both my 07 Avalanche and 07 Silverado (both AFM 5.3L) have a rough idle. I bumped the idle up using a tuner to 750 rmps and it leveled out the rough idle. I think that the low idle RPM is the cause.

 

Klydel, the EGR valve is controlled my a solenoid and the computer, if one is not working correctly it will cause this.
A simple test for this simple problem is to pull off the vacuum hose to the EGR valve and test run it, cleared mine up on a Caprice.
If this does not work I am going to blow everyone away by my next suggestion.

 

Klydel- If mine gets worst I will take it to the dealer but right now it is so slight. Also what kind of gasoline grade are you using? When you are in idle and it shakeswhat are your RPMs?
I use 91 and my RPMs at idle are 500 and then bumps up to ~525 really quicklywhen it happens. Again when I have it happen it is very slight and I really have to pay attention to feel it.Lastly mine only happens when at a stop light.ZX on this board mentioning using Techron which I may try next as mentioned on this post https://chevroletforum.com/m_47911/tm.htm

 

I also forgot to mention that ZX mentioned our Tahoes are not tuned for the higher Grade of Gas. Therefore along with the Techron I may try a lower grade.

 

Techron is what im going to use on my next fill up...... My tahoe also idles at 500 rpm ....... very common (rough idle)

 

There is another thread on this. Try doing a search. Basically the very slight vibration is normal. The slight vibration/ rough idle has become non existant after 3000 miles.

 

Well,
I took it into a different chevy dealership to have them check it out, they ran pulse widths, and duty cycles - all came out within normal limits. They said it looked fine and that some of the V8's will tend to run a little rougher than others in idle. After looking at other message boards, this sounds like a common problem with Tahoes.
Some say that Techron fuel cleaner helps, putting on more miles helps (2500-3000mi) as well.
I'm going to drive it a little more and make a decision. How do you request a new car when it's such a light shake, intermittent, and all testing reveals that nothing is wrong.
Thanks for all the help, any more advice will be greatly appreciated.
Klydel

 

You don't.