My daughter e mailed me with this problem. She said she filled the car and after several miles started running terrible and the check eng. light is on. I`m assuming crappy gas..water / debris. I had her change the fuel filter out and pump the gas out and re fill. Now assuming her husband has done all this correctly, she says the car still runs bad. I`m overseas and have no access to the car. I`m thinking maybe a fouled plug are bad injector. Is there anything else that could be checked? Thanks for the replies

 

Sounds like my CLK anytime I use Chevron gas. It hates it.

 

A 'Check engine ' light can be triggered by a loose gas cap but after all the other things you did this sounds unlikely unless she damaged it
In my ancient past, I owned a Saab that picked up a similar problem when I filled up a near empty tank. Rust in the bottom of the tank passed the filter and clogged the injectors and left me stranded. The gas tank, in my case, had to be replaced and the injectors cleaned. Gas today is much cleaner.Rust can sometimes occur in a tank from condensation that occurs if cold gas stored underground is pumped into a hot tank or vice versa when relatively hot underground gas is pumped into a severely cold tank. In either case condensate can occur, creating water which can rust a tank.