AUTO MECHANIC PROBLEMS (AGAIN)

[Durian Fiend]

So while we're at it...

2008 Impala with 29k miles (not a misprint) and vehicle weight certified by a weigh station, running rough or misfiring both at idle and while running.  Seems to be worse when its warmed up.  No check engine light and no codes showing up on scanner.

A quick internet search doesn't narrow anything down for me.

Hi, I’m new to posting here and I hope I did the reply thing correctly. This was exactly the situation with my beloved but difficult VW van. It would "normal" at first but got worse as it warmed up and after it was warm the idle could get so choppy it would stall on me at a stop or starting back up after a brief stop. My son told me to change the fuel filter before looking into the more expensive/involved other suspects like the mass air flow sensor. It sounded odd but didn’t cost much to try that so I asked the mechanic to do that and sure enough it solved the issue. Might be worth a try especially if you can do it yourself.

I was curious and looked this one up.  According to my search, the filter is located inside the fuel tank along with the fuel pump.   That's a real fun job, especially if the tank has to be removed from the car.