the initial start may take 5-10 seconds, but after the start, the car does fine. after driving it for a few seconds, i can restart the car without any problems. the problem will come back if you let the car sit for 10 minutes. what could be causing this? i had the fuel pump,fuel filter,spark plugs/wires,air temperature sensor,smoke tests, fuel pump fuse,fuel pump regulator and vacuum test performed and all of those things are fine. the check engine light is on, and the codes read that both cat converters are bad. i had aftermarket converters put on and they were tested and it shows that they are running efficient. even before the converters went bad, the car still had the same starting problems. any help will be greatly appreciated.
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1999 Audi A6 Quattro Question: hard initial start
Answer #1dandd February 22, 2009, 16:04Master
I have seen reports where the EVAP purge valve sticks open and causes a vacuum leak, which causes a very hard start. It sits on top of the Air Cleaner. When the car is starting it should be closed and should not open until the car is running and is in a 'purge' mode. I have talked to techs who have pulled there hair out for weeks before finding this. Hope this sheds some light. You can bypass it for testing purposes and see if cahnges anything. It costs nothing for this test. Another thing to consider is to look at the fuel trim, especially Long Term. Audi's tend to wear out their Mass Air Flow Sensors pretty quickly. The Long Term Fuel trim will be over 12 percent. This creates a lean condition which can cause a hard start. It may also have wiped out your CATS. When the car is too lean, the CATS are flooded with HC's and NOx and they get over worked and fail. I hope these tips shed a little light.
Answer #2spyder February 25, 2009, 15:48Journeyman
If during the hard start episodes you are able to confirm that fuel pressure AND fuel volume are correct , that spark is available and sufficient and you have no air leaks plug the evap as suggested and try starting with the MAF sensor disconnected.
Incidentally is residual fuel pressure maintained after shut off ?? Sometimes necessary for starting after hot shut off.
Answer #3galaxyreflex March 03, 2012, 02:43Enthusiast
what codes did you get for the cat codes because i am wondering if I need to change my 02 sensor or my cat