Engine Cut out while driving (1.9 TDI)

[nocoordination]

Hi guys,

Please bear with me as I am new to this forum lark, so only just getting round to some of the terms used.

First of all, my Audi A3 has a recurring problem. It happens when it feels like it, so there's no pattern, and I do apologise if other people have posted something similar. If the answers are in their posts, point me to the right direction.

I can be driving down the road when the engine cuts out. Everything else is on (Stereo, Lights, heating etc), but I notice that when the engine cuts out, when I try to sart the engine again, the pre-heater light doesn't come on (I know that if the engine is already warm, there's no need for it, however it flickers on to say that it's tested itself).

When the Pre-heater light doesn't show, the engine won't start. I have to wait for the test of the pre-eater light to flicker on before starting the engine, and then every thing is fine (until it happens again).

There are no warning lights showing apart from on exactly three occassions (not in succession either), the oil light has shown with the warning, although this problem has happened at least a hundred times.

Now I've been to the garage - they tested the computer on it. A report came up stating that the alternator and the rear right ABS sensor was knacked. I've had the alternator replaced, and I've also had the battery reaplced (as the alternator was overcharging the battery - which stopped it working too).

However, still not solved. The other day the car cut out (although the pre-heater showed up straight away, and started straight away too), and earlier tonight the car wouldn't start (I went to someones house, stopped the car, posted something and then came back to it not starting with no pre-heater light again).

WHATS HAPPENING?!?!?!?!? I love my Audi A3 and don't want to scrap it at all. I just want it working without the problem of going through absolutely everything and paying a fortune.

In one forum thread, I found that it could be the Engine Management Relay (is this the same as the ECU? - Not very technical with cars!). If it is the Engine Management Relay, how much is it to be replaced?

Also what's VAG-COM? It this the same thing as what the computer at the garage did? I was told it brought up some error codes that told the lady what was knacked.

Cheers!!!

[S2AVANT]

VAG-COM is the software that allows a computer to talk to your ecu. It is used to find fault codes i.e what is knacked.
If you can get somone to run VAG-COM on your car you will see what the ECU thinks is wrong with it. This is the quickest and cheapest way of fault finding on cars that are equipped with the system, especially on an intermitent fault, as the ECU stores the faults until they are cleared.

[nocoordination]

Now I understand what VAG-COM is, I can tell you that this has already been done. If you read my original thread, you will see that the VAG-COM brought up the Rear Right ABS Sensor ad the Alternator as being faulty. These has both been replaced, and still the engine cuts out.

Is the ECU a separate component to the Engine Management Relay or are they one and the same thing?

Any help would be brilliant.

[adamss24]

Now I understand what VAG-COM is, I can tell you that this has already been done. If you read my original thread, you will see that the VAG-COM brought up the Rear Right ABS Sensor ad the Alternator as being faulty. These has both been replaced, and still the engine cuts out.

Is the ECU a separate component to the Engine Management Relay or are they one and the same thing?

Any help would be brilliant.

Replace relay 109, that's supllying power to the ECU(engine control module) and give the said symptoms because its craks internally and the ecu thinks that the engine has been shut with the ignition switch (hence no faults stored in the controler's memory). I would start with that as its cheap, really ! If it does not cures the problem, you will need a replacement ignition switch...much more pricey and the keys may need codding as well !

[devonutopia]

If the engine is still cutting out, vag com should have more faults to read. It wouldn't (I mean shouldn't ) cut out if there was no issue the ECU didn't pick up.

Just read Adam's post - sure hope it's not too major.

[nocoordination]

Replace relay 109, that's supllying power to the ECU(engine control module) and give the said symptoms because its craks internally and the ecu thinks that the engine has been shut with the ignition switch (hence no faults stored in the controler's memory). I would start with that as its cheap, really ! If it does not cures the problem, you will need a replacement ignition switch...much more pricey and the keys may need codding as well !

I'm taking it to an autoelectrician tomorrow so I'll get him to check it all out.

Hopefully I'll get it sorted by this week!

Just to comment though, I had it in the garage today, and the garage man had taken the car for a quick run and it cut out on him. To cut a long story short, he said that he checked the solenoid and that when the car cuts out, the power to the solenoid it cut, which is making it stop. So I presume this is what the ECU is doing (to preserve itself?)