ok i have some questions to ask. i have a 04 a4 1.8tq with 73k on it. recently my car has been driving weird and other members on here told me it is my DV valve. but this was a month ago and i still haven't gotten it fixed because of money issues. so im driving it today and my cel light comes on and i assume its the DV valve because i haven't gotten it fixed yet. so my question is how come it took so long for the light to come on? would the DV valve make the cel light come on? if you wait longer to get it fixed what problems can it lead to? and since i haven't fixed it yet can it mess up my turbo or something? any help would be appreciated thanks!!!

 

so what exactly is wrong with the car?

 

when i drive it normal or without pushing on the pedal real hard it drives fine. but when i drive it rough or floor it my car starts to drive weird. it only does it when the turbo kicks in. say if u were stepping on the gas and then taking your foot off the gas but doing that repeatedly. thats what it does. someone else told me it was a diverter valve.

 

hmm, well sounds like it , trully i have no clue . but i would definitely cough up 150$ and get a new dv, like tomorrow

 

anyone else have anything to say

 

I would try to take the car to a local parts store and have them see what code you are getting. That way you know for sure if it is the DV giving you the cel. Also, you want to change the DV as soon as you can, since if it is acting the way you say, its causing a lot of extra wear on the turbo.

 

As to why it took so long to through a code, assuming you have a bad DV, the ecm will try as much as it can to correct itself before throuwing a code. It's like if you are stuck on a project and you wait until you exhausted all possibilities before you call for help.

 

There is no code that is specific to your DV or would tell you if you DV is operating at all, its not connected to the ECU. I would still get the car scanned and my guess is that its going to tell you there is an overboost condition. If you know someone with ross-tech it would be best. The DV can cause some funny things with the performance of boost and yours if it has never been replaced or upgraded is likely bad but I doubt that its the cause of your "problem". I would recommend scanning the car with ross-tech and possibly doing some logging. The problems with can actually be a number and or combination of events.
First, when did you notice this starting to occur?
Had you recently done any mods prior to this occuring?
Had the temperature started to drop as we approach winter?
That being said let me say that based off your initial description, it sounds like the engine/boost is reacting funny when you drive it hard, foot to the floor? The engine is acting like you are fluctuating the throttle? Like your relatively quickly applying and then releasing your foot off the accelerator? That sounds to me, possibly(and I mean possibly) like your throttle plate is opening and closing on you do to an overboost condition(soft limp). This is a safety feature built into the cars to protect the engine when the ECU determines that their is too much air flow/pressure. When this is determined the ecu restricts/cuts the throttle(even though your foot has the pedal to the floor)because these cars are DBW(drive by wire),which means the throttle plate rather than being controlled by a cable or other physical mechanism which connects the accelerator pedal to the throttle body, is controlled and operated electronically. So ultimately it's the ECU, not the driver, that determines the angle the throttle plate is opened relative to the accelerator pedal. (I would guess your revs fluctuate pretty quickly between 4000-5500 rpms).
This would tend to become more prevalent in colder temperatures because at cooler temperatures air is more dense. Higher density air = Higher boost pressure = Too much Boost for what the ECU is expecting and/or can compensate for = ECU restricting throttle = the condition you are experiencing.
I believe your MAP sensor is the main culprit in causing this condition and alerting the ECU to the overboost condition. I'm not saying your MAP is bad, with the cooler temps it's sounds like it's doing it's job.
I would check your DV and replace it if its necessary. Check is real easy to do. Remove it take a 8-12mm socket or what ever else place it in the nipple that makes sense and press down on the valve, with valve compressed place thumb on top of small nipple to seal and then release the pressure on the valve. If valve immediately returns to its original position DV is certainly bad. If the valve takes a moment or two to return and your thumb which has remained on the small nipple to seal it has suction to the nipple DV is most likely ok. Sorry about the novel not sure of your level of experience/knowledge and would rather attempt to be clear from the start. Good luck.

 

thanks i really appreciate your help. i just got back from the shop. i like that place because they don't charge for the diagnose. its called ingolstadt west check them out if you near Canoga park, ca. but it turns out to be the diverter valve. for the part and the labor it came out to be $164.07

 

Well it definitely sounds like there is "something" kicking in and out as you floor it. Most likely it's a valve but it could be your fuel system or something else in the intake system.

Good luck!!!