Hard starting audi a4

I own a 1997 Audi A4 Quattro with about 131,000 miles. Recent problem. Intermittent- engine cranks but car will not start. Fuel pump, fuel filter, and relay replaced. My mechanics are stumped. Problem seems to appear when car is driven at highway speed for about 10 mi. and then left to sit for about 45min. Bouncing the rear and front of car SEEMS to help and will start roughly after three or four tries. There is no gas smell but quite a by of exhaust one time when it happened. It also idles roughly for a bit once it starts. My mechanic has been working on German cars for a long time, but he is stumped. John

You Could Have One Or More Fuel Injectors That May Be Stuck Open.


Thanks. I will see if that’s something my mechanic investigated. He just replaced the cam shaft sensor. Don’t know yet if that was successful or not.