sometimes it just won't start, then a couple hours later fires right up???

Could be a bad ignition module/pickup coil or ignition switch.

Does it have any Check engine lights or codes? If not, I would suspect the fuel system, or some sort of fault in your anti-theft keeping it from starting. I had it happen in my truck once. It would fire right up, then immediately shut itself off and be fine a little bit later.

This might help: I had the same problem a few months back. The car would turn over and not start. But, eventually the engine would fire up (and run forever). My fix was to replace the CAMSHAFT POSITION SENSOR. Although, the new part is very expensive, I picked one up from a seller on eBay who was breaking. It did the trick and the car is as good as ever. Fingers crossed for you!

Could also be the fuel filter. If this is the case, you should have a lean fuel mixture code stored.

When this happens are you seeing the tachometer working?if no there is a possibility of a Crankshaft position sensor,is the CEL on?scan and see what codes are stored?On the 2.7L would take a very close look at all of the small vacuum hoses for splits.When it starts does it run smooth or is it rough and clears itself up?There were some issues with fuel injectors on some models as well.

I have a 2007 Audi A6 with a 3.2 liter v6..... I changed the crank position sensor, and the problem still remained, it turns over and won't start. Sometimes it takes a minute or 2 but other times it takes a day.

I have the same problem, about to try the crankshaft position sensor

Hey roger_Rabbit1 i have that same car same problem did you ever find what the problem is?

Hello, I have the same issue. Audi A6 2007, very low mileage & does not start at all. Battery & fuses working. Just sent it to Audi & still they are not sure what is the problem. Any insights! Could this me a defect in the model! Anyone knows any problem as this seems to be a potential recall problem. Thanks!

Does the engine turn over?

The problem I had was the fuel relay! When the car was warm it wasn't starting. Another problem could be that the injectors were leaking, they had a recall with that, the injectors will leak and flood the cylinders, that'll cause it to turn over and not start.

for me, the ignition switch housing broke.. it's costing me $800 + to get it fixed. The original part is custom to a VIN and needs to be ordered from Germany.

i am facing same problem...what could be reason?

Audi A6 2.4 2001 starts fine and drives , then you turn off and it won't restart leave over night it starts , had new starter and cam sensor , crank sensor ,temperature sensor ,had alarm tested and that's fine ,any help

none of you bottom bois gave good answers, check vacuum lines at rear of engine, they may need to be replaced

I have a 2003 Audi A6 Quattro 3.0 motor I put new coils new spark plugs and a new throttle body and a crankshaft sensor bank number 2 in my alley still won't crank up

My 1997 Audi a6 will crank but not start at times, once it starts it runs forever. I have noticed an additional indication of the problem. When I turn the ignition switch forward to the accessory position and leave it their, I.E. windows up or down heat fan running, the GAS indicator doesn’t move or register any level. If I try again later and the GAS indicator starts to rise then it will start. So I can tell ahead of time whether or not it will start. Any ideas???

My answer. i just want to say guys thanks for asist us

I had exactly this issue on a 2007 A6 3.L Quattro - 4F model Sedan. 1st I ran Liquid Molly fuel additive engine cleaner. Start failure seemed less often but still occurred sometimes. I then suspected it was a temperature related issue based on when it did and did not start, but this I think was an incorrect guess based on circumstantial evidence. I replaced engine temperature sensor in the top radiator tube then the two cam shaft position sensors. Start success rate seemed to increase and I thought the problem was solved, but alas no. So then I bought a scan tool (Foxwell) and pulled engine fault codes 01378 & 01671. This relates to Relay J271 (in the front left relay/fusebox in engine bay - tricky to get to, wipers need to come off). 70W relay. There are two identical relays in this box with the ECU so I swapped both, original part 8E0 951 253 replaced with compatible new part 7M0 951 253 A (12v 80A relay). About USD$12 each. So for the engine fault code that would appear on a start failure (proven) it has not reappeared. New relays are the black ones marked with 100 on top (see photo). Not sure if this fuse box is on opposite in a LHD model, my car is RHD.

The problem I'm having with my 2001 a6 2.7 is it will start right up and run for about thirty minutes then just dies. About fifteen minutes later it starts right back up. New fuel pump and maf sensor. Any ideas?

My fix for the starting up problem was a new ignition switch. Hope this helps someone.

One I recently heard would not start, had a burnt ignition switch, havr learned this is an expensive part to replace.

Hello, I have the same issue. Audi A6 2007, very low mileage & does not start at all. Battery & fuses working. Just sent it to Audi & still they are not sure what is the problem. Any insights! Could this me a defect in the model! Anyone knows any problem as this seems to be a potential recall problem. Thanks!

I have Audi A6, 2005 3.2L Quattro. It start well but during driving suddenly shut off with a jerk and then auto start again without any trouble. It happen 1time daily during my way to office. Any idea, what will be the issue with my Audi.

I have the same problem with my car. 2009 audi a6 3.0l V6 Quattro. Car starts first time in the morning and drives perfectly. If I turn the car off, and try start again, engine turns but doesn't get to idle. Car will eventually start anywhere between 5 - 20min later with black smoke and uneven idle. Once the car is in motion and driving, drives great but again with black smoke. Any ideas are appreciated.

All you guys should look at the cam follower or vac lines. Pressure testing For boosted cars is a great way to find bad hoses and you can build your own easily. I think my A6 tranny is about to crap out, anyone have a spare? Fixmycar@allautotx.com

I have same issue it tells me to put clutch pedal in it's in and engages into every gear reverse even blinks and says it's in gear but it will not start and same if I leave it alone for a while it will start just fine but this is happened to me twice now one sitting at a stoplight and I had to push it to the side of the road and just this morning when I went to work left it idle in neutral with E-brake on to go clock in its died and then will not start

I have a 99 Audi A6 Quattro, recently has not been starting after driving it. It starts fine sometimes then sometimes it won't turn over at all even though I have power. If I leave it till morning it starts right up. Thought I could be the stater ir starter relay... Any Audi geniuses have any ideas?

Hi. I have a 2013 Audi a6 supercharged. Yesterday evening the engine started fine. Then when I jacked the car up to see were the coolant was leaking and then lowered it back done to move it to another place since I wanted to move the car to away from the puddle of coolant so I could get under the car. But then the car wouldn't start. When I took out the belt, the engine starts fine. Tye mechanic says something have gone into the supercharger, since the plastic hose from the air filter to the supercharger is cracked and covered with tape. Please help.

I had similar issue; it was one of the fuel pumps gone bad - there is a low pressure and a high pressure fuel pump in my 2012 Q5 3.2

My 2006 Audi A6 Quattro 3.0 TDI was fine until the old battery died. Unbeknownst to me, and every mechanic to date, you can't just replace the battery. Audi have a battery management system (BMS) calibrated to specific AGM batteries. When replacing the battery, the mechanic should reset the BMS. In my case, the idiots at Battery World just put in a battery. Even though it is fully charged, the computer thinks it is almost flat and then turns off all electrical components, even the ignition. A German mechanic might know about this but here in Australia, they look at me as if I'm a three-headed alien bringing them news of the impending destruction of planet Earth. Audi are also at fault because of their secretive approach to everything. They want you to go back to an authorized Audi mechanic for everything and pay a lot of money. But even here in Australia, Audi employ idiots that I had to educate on this matter. So, if your Audi has a BMS, make sure you have the correct battery installed and your BMS is reset.

Hey man have you ever found out what was the problem I got a 2006 Audi A6 Quattro that’s doing the same thing no dash lights no crank no head lights radio good but my window don’t work & seats good