Audi hesitates, back fires a little,or doesn't go at all!

I have a 2000 Audi A8 156000 miles 4.2 motor.

Hesitates when I step on the gas or does nothing all.Sometimes it will rev up and sound ok. Check engine light came on when it was going to stall then went off.Dealer tells me timing belt problem $2500.00,major tuneup $750.00,or $15,000 new motor.New motor isn’t going to happen. Do you think timing belt is the problem.What is involved to do this?

This does not sound like any of the things you’ve mentioned. A timing belt problem or a clogged fuel filter is not going to be an on and off affair such as you have.
Did no one scan the car for codes?
Offhand, I’m leaning towards a failing fuel pump. Running a fuel pressure and fuel volume test along with checking the fuel filter would be the first thing I would do other than pulling codes. A partially clogged fuel filter can allow the car to run fine but will eventually kill the fuel pump.

If this car has never had the timing belts changed then you’ve been on shaky ground for a while because it will be real expensive whey they do break.

That CEL (check engine light) is just a kid in class waving her hand trying to get you attention because she has the answer. You need to have the codes read. Some places will read them for FREE. Try Autozone or Advanced Auto Parts. Get the exact code (like P0123) not just their translation into English and post it back here.

Dealers are no better (or worse) than independent mechanics for almost anything you might need done on your car.  They will almost always charge more per hour and often more for parts and supplies.  They also tend to look at repairs a little different than the independent. 

A dealer may well recommend work that strictly may not be needed, but could be connected to the problem or maybe replace a part when a little repair would fix it ALMOST as good a new.  

There is no need to bring your car to the dealer for any service other than service that is going to be paid for by a recall or original warrantee.  During the warranty period be sure to document all maintenance work.

I suggest that most people would be better off finding a good independent (Not working for a chain) mechanic. 

[b] Timing belts should not be put off.  If they break they can cause very serious damage to your engine. [/b]

Are there any Euro import independent mechanics around? Visit one of those places.

The timing belt is likely unrelated but if it snaps and your engine is interference your get an instant upwards of $15000 bill for a possibly new engine. I think that is what the dealer may be telling you and not to ingore your timing belt.

How much?

Try another shop. I agree with others that it sounds more like a fuel delivery problem. But that shops prices sound awfully high to me.

Many thanks to all,your good advice is sending the car out to a import shop for an anwser to the problem.I need to get the problem solved first ,timing belt second.