S4 just shuts off while driving
 

HELP!!! My 2001.5 S4 began to shudder every now and then which I know to be a misfire. There was no pattern (not during acceleration or bumps). Well I began my 6 hr drive home for Thanksgiving and I felt the shudder and the car turned off!! The misfire is occuring on ALL cylinders simultaneously. Some times it starts back up but about 4 times I had to pull off the high way and wait and try to start it. The EPC and CE light comes on when this happens. The most peculiar thing is that when the car shuts off (or will not start) I hear a clicking noise. The lights do not dim and the battery voltage remains above 12V. The clicking is underneath the TBB (Throttle body boot). I turn the key to "run" (not cranking) and it just clicks under there. When the clicking stops the car starts and runs fine. This happened at 9:30PM tonight so I have not had a chance to go and get the P codes. I will post them when I get them. So... What could it be? MAF, Ignition Control Module, ...??? Please HELP!

RE: S4 just shuts off while driving
 

What could it be. Good question. Could be alot of things such as fuel pump, ECU, bad ground. etc etc. Post those codes...

RE: S4 just shuts off while driving
 

More details... I was on my way to Advanced Auto to get my codes and the car died in the driveway. I still don't have the codes but I have more info.

The clicking is on the throlle butteryfly valve that the Throttle body boot attaches to. I unplugged it and it stopped clicking. More importantly there is a clicking behind the dash. I removed the fusebox and looked past it toward the front of the car and saw what I think to be relays. Is a relay involved when controlling the throttle valve? If so which one? Thanks in advanced!

RE: S4 just shuts off while driving
 

well im going for the alternator/battery because that exactly what happens when the battery is dead but if you leave it for a couple of mins it will start up and that's because the battery has cooled ( ALTERNATOR );)

RE: S4 just shuts off while driving
 

I once had a similar problem to this but not in my s4 I had it in my 98' M3 but it turned out to be loose wires in the ecu and rusted ends, IDK if it could be a mold issue or something around the clips to your ecu, but I'd check the ecu clips for water or rust. COuld fuck up everything in the ecu. But I also agree with techbod because I have read about a problem like this in euro tuner like that so could be a few things.

RE: S4 just shuts off while driving
 

Thanks guys. I will be checking the ECU next... I know it is not the battery or alternator.. it cranks just fine and lights/radio work fine.

I have some more details. I finally made it to advanced auto and I have NO faults so whatever is happening the ECU does not know it or record it. I know that if I remove relay 372 the clicking stops. I think whatever is controlling the 372 relay is at fault. I am also going to be checking the connections behind the relay. I also pulled the relay apart and cleaned the contact and checked the coil for spots. The relay looks fine. SO.. what controls the relay? Thanks.

RE: S4 just shuts off while driving
 

I have been reading more. Anyone have any experience with a failed ECU power relay? That would explain why there were no codes logged. Or.. could be a failure with the Immobiliser control unit which locks the ECU. Anyone have these failures before?

PS. It is definately not the battery or alternator.

RE: S4 just shuts off while driving
 

I would stop driving it, & get the codes! Start from there, then do some simple Vag-com test.

If it's not a simple voltage problems (battery & alt) then you might have a multiple other things going wrong.
When you turn the car on, but do not start it, what is the voltage gauge at? When you start the car what is it at?

There are so many place to start, it's not even funny, maf, CTS, plugs, TB, big boost leak, cam sensor, coil amps......

RE: S4 just shuts off while driving
 

There are no codes!!! I made it to Advanced Auto and had an old P1113 from an o2 sensor I have yet to replace but no others. I cleared this fault and confirmed no codes. Then I started it up and as luck would have it the car shut off and started its clicking. I then checked the codes and there were NONE. I unplugged the MAF which should force the car to use factory defined maps in the ECU and the car did not start (so not the MAF?). The voltage is reading a steady 11 V while it is not running. I am sure it is not battery or alternator issues. Since the ECU does not have any codes I am thinking the ECU supply power may be dipping too low. Maybe the relay which powers the ECU? The other thought is that the imobiliser is locking the ECU while driving. I have found an Audi Master mechanic at a local ford dealership so I have left the car with him. The next step will be for me to order VAG-Com and check the ECU supply voltage, fuel pressure, and coil voltages (if available). Thanks for your post.

RE: S4 just shuts off while driving
 

Good luck, I'm sure there are some stored codes that will pop up with a Vag-com.

There is no immobilizer with the US S4, just the ROW ones.