so i went to test drive a 2007 audi a4 2.0t quattro and when I would accel hard it would hesitate and feel like the governor was kicking in at around 70 to 80mph then the check engine light came on. so i stopped and tried to accel hard again and same thing but this time is happened around 30 to 40mph i told the dealer and they said they put in regular gas instead of premium and that could be causing the issue any ideas car has 117k on it and the carfax doesnt show any work beside minor check ups

 

I would guess the diverter value is bad. Mine would do the same thing when it went bad. If I remember right it was an $80 part and if you are inclined you can change it yourself. I had the dealer change it and paid just under $200 total. Forgot to add this is a common issue with these cars. Once you replace the valve you get the updated model and shouldn't have to worry about it further.

No, I do not think regular gas would not cause that (I have put regular in mine before with no issues). If the CEL came on ask them to pull the codes.

**EDIT: Okay, I just read the above line and have no idea what it is saying. What I meant to say is that regualr gas should not cause the problem you are seeing.**

 

You really need the CEL code to diagnose it, but my guess is the diverter valve as well. Mine went bad (it's a diaphragm and ripped a tiny bit) and was fine until I got on the gas hard. Then, it throws P0299 Underboost.

 

So they told me it was the gas prrssire senser or something like that. Would that cause it to hesitate? If its just a sensor

 

I would think so. If the sensor tells the engine to increase or decrease fuel pressure that could cause a hesitation.