Really need help with this problem

[kevwall]

For the last 8 weeks now ive had constant problems with starting my car and every so often it cutting out and not restarting back up, its been in and out the garage 3 times and they still find it a mystery what is up with it (bearing in mind this is an Audi specialist im taking it to), so ive took it to them again yesterday and theyve rang me saying my battery is flat and i need a new one, but still im not convinced this would cause my car to cut out when driving at 40/50 mph on a long straight road, fuel filters been changed, diagnostics have been put on the car and no one seems to know what this problem is, could anyone help or does anyone have ANY idea what the problem could be?

[phil miller]

hi mate what age, model, engine and mileage does your car have?

[kevwall]

It's 2006 Audi a3 2.0 TDI Auto DSG and mileage is 151000 , full audi service history too

[phil miller]

It's 2006 Audi a3 2.0 TDI Auto DSG and mileage is 151000 , full audi service history too

right ok, i had a feeling you were gonna say its a diesel, now when it cuts out and doesnt start have you noticed if the ECU light is on when you try and start the car? when its been plugged in to DIAG what codes have been in the ECU?

now ive had a few (3x 140 TDI's) that have had a problem similar to this, the first one i had would cut out just like yours take forever to start but had no codes in the ECU, BUT when trying to start it there wasnt an ECU light on when the IGN was turned on before cranking (hope that makes sense?) the other 2 at about 40 mph loss a little power and when slowing down cut out, after checking all the normal bits i got to the fuel lift pump in the tank, it was getting its feed but the pump wasnt pumping, replaced the pump both were sorted as for the first one after checking it thro and then checking for lives and earths at the ECU i decided to send the ECU away to be tested, had a phone call telling me the ECU was wet inside and they had to replace something, had it back, refitted it and hey presto it was spot on, now ive also had the ECU with water in it doing the same as yours on a mk5 1.9 TDI golf and cured that, the ECU is under the scuttle panel, under the wipers and is prone to getting wet, could be that mate, worth a check, as to is the lift pump

[kevwall]

No lights come on , but like you said at 40 mph it dies off then when I come upto a junction at low revs it cuts out al together, it cranks but doesn't start, I'm getting that annoyed with it that I'm ready to sell up and get something else!!! Going to tell the garage about the fuel lift pump and see what they say about it! How much are you looking at to replace that ?

[phil miller]

No lights come on , but like you said at 40 mph it dies off then when I come upto a junction at low revs it cuts out al together, it cranks but doesn't start, I'm getting that annoyed with it that I'm ready to sell up and get something else!!! Going to tell the garage about the fuel lift pump and see what they say about it! How much are you looking at to replace that ?

IIRC the lift pump is £120, best thing to do is when it cuts out check to see if you have diesel pumping out of the input to the fuel filter, if you do then its not the lift pump if you dont then its the pump, after the car has died on you if you turn the ign off and then on again does the ECU light come on?

[kevwall]

It only comes on for a few seconds like it does on every start up with all the other lights that usually come on, it's never came on and stayed on, strange !!

[NHN]

Has the fuel filter ever been changed?

Yeah the under seat pump is one to look at as mentioned, this is £160 new, tandem pumps are another, injector looms, injectors.

Is the alternator charging ok?

[kevwall]

Yeh fuel filters been changed 3 times since November , wouldn't an injector not show up on diagnostics though? And wouldn't it misfire ???

[NHN]

Not neccessarily no, had a 170 tdi just wouldnt start until I disconnected the injector at fault, showed a silly relay fault that wasnt even related.

[kevwall]

My car runs fine for a few days then it'll shudder as I'm driving then when I come upto a junction doing Low revs that's when it'll cut out, seems strange that everytime I take it back the cant pin point the problem!

[NHN]

Alternator charging issue, get this checked aswell.

[kevwall]

Thank you for your help I'll let you know how I get on !!

[Gomjaba]

Had this twice now (different Audis), once it was a problem with the power blocks, and the other time the lambda sensor. Bear in mind, mine were Petrol and I have NO idea about Diesel engines (well, engines, full stop).

[Mike Foster]

Injector wiring loom has also been known to cause this problem which does not show on diagnostics as far as I know.