07 2.0T randomly shutting off...HELP!

[rob53815]

Hey guys (and gals) so I've had an 07 A4 2.0 T now for about 6 years (CPO) and in that time it's been solid as a rock, given me no problems whatsoever and I've kept up with maintenance pretty well . Wednesday evening (2-5-14) leaving work I get in and turn the car on with no problem at all like i've done the 20,000 previous times before that lol... A few minutes later I make a pitstop and when I get back in the car and turn the key, the car DOES NOT START. I hear the starter motor doing its thing with no problem but the engine just isn't turning over, and I try it a few more times after that but nothing. I call up my friend to see if he can come give me a jump since I'm thinking weak battery or something and in the 25-30 mins i'm waiting for him to come through I decide to give it one last crank and boom it comes to life right as he's pulling into the parking lot. He works at Autozone and suggested I swap the battery out and see if that might be the culprit and eliminate that possibility since its still under warranty so I did that on Friday (2-7-14) and the car started up no problem at all. About 10-15 mins after we finished the transaction I go and start the car and it starts with no problems but when I start backing out of the parking lot... IT SHUT OFF ON ME AGAIN. We tried cranking it a couple of times and again the starter is turning and spinning but the motor wasn't turning over. There's no "check engine" lights or messages on the cluster but just for the hell of it we tried plugging up an OBD II scanner and to no surprise it revealed nothing to us. About 20 mins later after we've racked our brains thinking of what it could be he decides to turn the key and BOOM it came to life and I left the place and made it home 30 mins later with no drama. Does anyone have any ideas what causes this, what it could be, what's the fix? Is this a common thing with these 2.0 motors? I'm trying to avoid dealer or national service chains if I can. But we're both stumped on this one....HELP!!

[4rings5stars]

Few thoughts...

-Fuel pump
-Crank sensor
-VagCom scan tool for a more accurate diagnosis

Thats just off the top of my head this morning. Hopefully others will chime in.

[aluthman]

Few thoughts...

-Fuel pump
-Crank sensor
-VagCom scan tool for a more accurate diagnosis

Thats just off the top of my head this morning. Hopefully others will chime in.

I'd say crank sensor based on what I've read. I've never had one go out on my car though. I don't think this is incredibly common with these cars, but as they get older it may start to pop up more. Definitely get it scanned with a vagcom to see if there are any codes stored that aren't throwing a CEL.

[B7Joe]

Fuel delivery issues maybe? LPFP? Lots of experience with fuel issues here, so I'm sure these guys will chime in.

[rob53815]

Someone mentioned to me faulty or about to fail ignition coils. I'm under the impression that they'd trigger a CEL if they were faulty though. Does this sound familiar to anyone?

[4rings5stars]

I'd say crank sensor based on what I've read. I've never had one go out on my car though. I don't think this is incredibly common with these cars, but as they get older it may start to pop up more. Definitely get it scanned with a vagcom to see if there are any codes stored that aren't throwing a CEL.

Eh. About as commonplace as any other make. Which is to say not too often

Someone mentioned to me faulty or about to fail ignition coils. I'm under the impression that they'd trigger a CEL if they were faulty though. Does this sound familiar to anyone?

Not unless all of them simultaneously failed to give you a no-run condition

[ColoradoBob]

My B5 Passat (1.8t) was doing basically the same thing. It always recovered and didn't throw a code. Finally happened while running and it threw a code for intermittent loss of the crank sensor signal.

I'd bet you have a crank sensor failing

[Biged243]

You said you are hearing the starter but the engine isn't turning over, are you sure the engine isn't turning over because that sounds like a bad starter that isn't engaging. It will spin but the sprocket won't engage the tooth ring on your flex plate or flywheel don't know what you have.

[BenMTL]

100% one of the following, had similar issue in the previous;

-problem is electrical in nature
-low pressure fuel pump starting to go bad
-fuel pump control module starting to go bad (rear, try this first, cheapest fix)
-ground somewhere near the rear fuel pump

I replaced my rear fuel pump control module as it was making grounds intermittant (sometimes could start my car, sometimes cant, sometimes died automatically) before it completely died. ~$250 part and 2-3 hours worth of labour in a heated garage for 2 people.