Engine died twice...

[Lloyd]

OK, so I've got a new problem and would appreciate advice to help get it fixed.
Yesterday, I was driving along at 70mph steady cruise and the engine cut out on me, it wouldn't bump start, dash clocks off apart from red battery light. Got to hard shoulder, turned ignition off and on and it started first time, no problems.

70 miles later, same thing happened, but this time I quickly turned ignition off and on whist still moving and it bumped itself alive.

I'm off to Spa and the Ring in 2 weeks so gotta get this fixed. Haven't checked fault codes as yet, will do so ASAP. Anyone got any ideas? Thanks to those who've already given me some pointers.

[A80Avant]

check the earths of the ECU to the Inlet manifold. They are under the manifold above the PCV valves.

check all earths for that matter!

[Lloyd]

Thanks - I will check them. (how many are there?)

[irishs2]

Exact same thing happened mine. Turn ignition off, and on and on it starts right up. My error codes where showing intermittent short to ground on G40 (camshaft sensor). I have just changed it today and hopefully it sorts it.

[Lloyd]

Exact same thing happened mine. Turn ignition off, and on and on it starts right up. My error codes where showing intermittent short to ground on G40 (camshaft sensor). I have just changed it today and hopefully it sorts it.

OK, that's the Hall sensor right? Someone else suggested that was to blame. Hmmm...
Trouble is, I struggle to follow the logic; With the engine is running, you can disconnect the Hall sensor and the engine will not stop. So, by that thinking even an intermittent error on that sensor 'shouldn't' cause the ECU to shut down the engine. Right? Wrong?

[macspring]

I would tend to agree with you re the G40 sensor, but for peace of mind maybe change it, (depending what others suggest), given the trip ahead ?

Maybe not, but could it be your ignition switch, not too dear to replace ?

Hope you definitely nail it.

Keen to see what it turns out to be.

Best wishes.

[GT500]

Ignition switch. Changed quite a few over the years.

[UrS4boy]

Trouble is, I struggle to follow the logic; With the engine is running, you can disconnect the Hall sensor and the engine will not stop. So, by that thinking even an intermittent error on that sensor 'shouldn't' cause the ECU to shut down the engine. Right? Wrong?

In theory, you are correct about the G40 Hall Sensor not being required once the engine is running. However, on my side of the pond there has been at least one case of intermittent engine stalling that was *eventually* cured by a new G40. *IF* you want to try it, here is some G40 info, including a hyperlink to a very detailed DIY replacement procedure:
http://forums.quattroworld.com/s4s6/msgs/22580.phtml

All that said, I would also suspect your ignition coil therm fuse. Lately there have been a couple of cases of the same symptoms as yours that were cured by replacing the thermo fuse with a normal 15A spade fuse. For an AAN, this fuse is the S64, shown below.

Or it could just be a bad ignition switch. I would start with the ignition switch because even if it is good now, it will likely fail soon anyway.

[Lloyd]

Ignition switch. Changed quite a few over the years.

Thanks - any tips on how to change the ignition switch? Does this mean needing new keys?

[UrS4boy]

Thanks - any tips on how to change the ignition switch? Does this mean needing new keys?

It is just the electrical portion that needs changing, not the key portion. You need Item 5 not Item 3. (Check the PN, it might be USA not UK)

[Jas11n]

Another vote for ignition switch.

Remove steering wheel (if airbag type, get your head down under drivers parcel shelf and see the little square access flap, open it and disconnect the connector clipped on the back - this disconnects power to airbag - no faffing with battery)

Remove lower and upper column shrouds, remove two screws holding in instrument cluster, wiggle it out of dash and disconnect plugs on the rear (pull coloured tabs up on the connectors before pulling them out. You'll now be able to see ignition switch on the back of the barrel.
Get a small flat head jewelers screwdriver and remove the paint Audi applied over the two tiny screws holding the ignition switch to the barrel. Undo the two tiny screws (being VERY careful not to drop them down into the mess of wiring) Pull ignition switch out and reverse to put it all back.

** The connector under the drivers parcel shelf is exactly what it's for - powering down the airbag for removal.**

Of course you can do this without removing the steering wheel, it's just a lot easier getting in and seeing what you are doing with it out of the way.

HTH's
Jase..

[UrS4boy]

C4 UrS Ignition Switch DIY pdf

Thanks - any tips on how to change the ignition switch? Does this mean needing new keys?

To complement Jas11n's words, here is a pdf for a C4 UrS ignition switch DIY that might help as well (the photos will be similar for a B4 (I think))

http://12v.org/urs/IgnitionSwitchReplacementDIY.pdf

[Lloyd]

Thanks everyone! I will get this switch changed and keep my fingers crossed.

[prj]

Did not even think of the ignition switch.
I agree, that's probably where the problem is.

Good luck mate, and let us know if it solves it.

[Lloyd]

Did not even think of the ignition switch.
I agree, that's probably where the problem is.

Good luck mate, and let us know if it solves it.

Time for an update. I changed the ignition switch last week and although have only covered 20 miles since, the car has already cut out and died on me once. As before, just a quick off/on with the keys and the car bumps itself alive again.

I'm back the drawing board and although it sounds unlikely, as more than one forum member has suggested it, I'm wondering about the hall sensor. It was changed last year during the cam belt service but hey, maybe it could the fault?

I suppose it could also be either of the flywheel sensors? TDC and speed. Are these easy to get at and change?

As I'm scratching my head again, and have only two days before a big road trip to Spa and the Nordschliefe I'm all ears for more suggestions and analysis