My audi 6 quattro 2.8 1998, when the temperature touch 90c the engine get stop and wondt start for start till become cool.

SOURCE: Audi 80e 1991 hard starting when cold

I've owned the same car. Check that the fuel relay 'primes' the system before you start the car. When you turn the key to the on position (all you dash lights, ready to start) you should hear the fuel pump run for a second or two. If it doesn't run you can replace the relay for about $30. If the relay is not the problem, it may be a check valve within the fuel line to the engine. This valve keeps fuel from draining back to the tank when the car is sitting. That way, there is fuel close to the motor when it's time to start. The temp senor was not a bad shot, they were thinking it was bad sensor not telling the cold start injector to run. Obviously not the case. However, the injector itself may be faulty in some way. As long as the car always starts, it's one of these problems, assuming the ignition system and engine mechanicals are in running order.  good luck. JK

SOURCE: 1994 Audi Quattro 90 engine wiring harness to TPS

If you want a good selection id try a parts locator. One place that can find you a good short or long block for a [URL="http://www.texas-junkyards.com"]Audi A4 engine[/URL] is [url=http://www.texas-junkyards.com]TEXAS Junkyards[/url], Junk Yards in TEXAS TX salvage recycler. They have a link somehow to multiples of thousands of recycling centers and will locate the best one for you.

SOURCE: problems with my 1995 Audi A6 QUATTRO

replace the coil pack, sounds like it is over heating.

SOURCE: start and stop audi

check your crank position sensor for resistance and check if the resistance comes out to what it suppose to be.if not then you need a new one...i think the range would be 2200 to 3000ohms but i would refer that you check the specified resistance before you check it. i hope that would solve your problem

SOURCE: Will These Spark Plug Wires Work for My Audi?

No. I would go with the cheaper set.