I have an 04 2.7 with 60k on the clock. brought it to the dealer for a surging problem on deceleration. (almost feels like warped rotors even though I'm not on the brakes). they checked for codes(none) and road tested the car. They asked what kind of gas I use, I admitted to using 87 on occasion. Tech said there's your problem and recommend 93. This is my 1st. Audi, are these cars really that sensitive? Has anyone else had problems because of fuel?

 

Wilkommen to the forums.

The 2.7T is pretty sensitive to octane. they come tuned from the factory for 91 (IIRC). ECU should compensate for knock from 87 but it comes at a cost (running rich). That may cause your surging problem but I'm a little suspicious. You say "they checked the codes and road tested the car". who exactly is "they". Was this at an Audi dealer or a used car dealer? Is this the dealer that you purchased the car from? Do you have an Audi or European specialist near you that you can take it to? You should at least have it checked out by an independent shop (if you haven't already).

Them blaming the gas, to me, is them admitting that there is a problem. Try some high test and see if it helps.

good luck.


*for future posts you may find more help in the model specific sub-forums.
keep us updated.

 

Thank you for your reply. It was an Audi dealer in my area. It was checked by an Audi tech and the service writer. I'm going to use 93 from now on. I'll post if that was actually the problem.

 

Well I've been using 93 since my last post and unfortunately no change. Car is surging at speed while coasting. It's driving my crazy! I've replaced the plugs, air filter, fuel filter, checked for vac leaks, removed and cleaned the tb. Car runs perfect otherwise. Plenty of power no hesitation. Just a pulsing in the engine while coasting to a stop. 200 rpms or so. Audi said they cannot duplicate the problem. And there are no codes. Any thoughts? Can this be a maf sensor going bad?

 

I also checked both dv's. I'm at a loss.

 

could be the MAF but it would probably throw a code (you did check right?). Fuel pressure regulator? Throttle body boot? fuel pump/filter? sticky valves?

does it seem to wobulate when sitting at idle or only when decelerating to a stop? Auto or manual trans?

 

It's only surging during decel. Idle is smooth and acceleration is smooth. I did unplug my maf and it ran the same. I expected a large difference in performance with no maf. If it was fuel related wouldn't I have problems under wot? Today i removed and inspected the tb boot, no cracks or wear It's an automatic btw, sorry for not posting that.

 

I took it for a ride today for a little test. Surging is in drive, sport and tip modes. Starts at around 3,000 rpms and continues until about 1200. Just a subtle bounce of the tach that gets worse as the car slows. I was trying to rule out a tc problem.

 

i'm racking my brain and not coming up with much.

the TC problem that gets mentioned on a regular basis is an '01 and earlier issue. not saying it isn't possible on your '04 but not the first thing that comes to mind.

you're right, most of the hesitation, shuddering problems that people report are under heavy throttle. I haven't come across a lot of information about it happening during deceleration.

I'll give it some more thought and research and see if I can come up with more ideas.

good luck

-not an expert just an enthusiast

 

Thank you so much... I cleaned the maf sensor tonight, no change. Ive been reading the Bosch sensors are problematic and are replaced on a regular basis. I'm leaning toward putting in a new one. The car runs exactly the same with the maf plugged in or unplugged (except for the stability control light being on). I appreciate your help.. I'm becoming obsessed with figuring this out!!!