I bought this low mileage (85,000) C4 in the spring and everything seemed fine. Now that summer is here, if the temp goes above 230, it will run OK at a steady throttle but does not like to accelerate, either from a stop or to change lanes, etc.

At a stop sign the car idles fine but when you push the throttle down (in gear or in neutral) the bucks, jumping between "I want to accelerate" and "I want to die".

Giving it 100% throttle does not help but as soon as you go back to steady speed it seems OK. I've only heard what sounded like a backfire one time.

It seems to average about 19MPG, I'm not sure if that is normal or not.

And like i said, below 225 it seems to run fine. I'm going to stop by a friends shop tomorrow and see if there are any codes stored.

Any suggestions on where I should be looking?

 

Welcome to the forum.

The first thing I would do is check the fuel pressure. 230° does sound a little bit warm. Have you check the cooling system such as thermostat , lower radiator hose, etc.