So I've read a couple threads about this I have no codes but when I'm driving and I hit that 45 or 44 mile an hour the needle goes up and down and it sounds like the car's going idling rough and then when I pass it and hit 50 miles an hour the car is smooth as a bell so I don't know what's going on everything is connected it idles nicely I don't know if it's an injector I don't know if I should clean something has anyone done it and it fixed the problem let me know please

 

Idle speed should be around 850 rpm. I can't imagine you're anywhere near that at 45 mph. Which needle is fluctuating? Is this an automatic transmission?

 

Sounds like the torque converter lock up , surging

https://www.chevyhhr.net/forums/prob...problem-31305/

 

Do explain what you mean by idling. May not be the same thing as most people mean.