Help - Audi A4 juddering/loss of power/EPC light on..

aftershxck · 24 Apr 2008 at 21:40

Hi, I need some help with my mum's Audi A4 please!

On Sunday night I was revving it quite high in 1st/2nd gear (3/4k RPM) and I think this somehow 'triggered' the problem, but I've often done this so I don't see it being that bad of a thing.

At idle, the car now sometimes judders, then when doing speeds of 80+ on the motorway, it judders quite a bit and sometimes it feels like the car is giving some resistance. Acceleration also often stops working on the motorway and even if I press all the way down on the accelerator there is nothing - zilch. It also doesn't feel as powerful in 3rd/4th gears.

Then today the symptons reached their peak - just joined the motorway and then at round 80MPH the EPC light came on and lost ALL power... luckily the services at J21 were a couple of hundred meters away so could get into the station easy enough - restarting the engine and the EPC light had gone and the car was fine all the way to work (25 miles).

Now I've done some googling using words like Audi A4/juddering/EPC light and so on and this seems to be a well documented problem amongst VW group cars, I've scribbled down some summarised notes on what it 'could' be as follows:

Someone with a 2001 Audi A4 had same problem - turned out to be crank sensor which was cutting the acceleration
Something about the 'coil pack' ? or ignition coil ?
Could be anything to do with spark plugs/ignition coils/fuel injector rings/valve cover gasket ?
Need to ideally scan the chip in the car to get the codes, using VAG-COM (?)
Could be an electronic pedal fault ?

Now I'm no car expert so most of the above makes no sense to me - my mum and I visited her mechanic friend who said that, as mentioned in the list, the car error codes need to be read using a VAG-COM device - however he said the error will only show when the EPC light is on.

Is this right? Because the EPC light has only come on the once (today) but didn't stay on - surely any previous errors are logged on this chip?

What would you suggest I do? I was considering some options and I don't want to have to start replacing everything when it could just be something simple - and theres no point going to a garage with VAG COM to check the car if the checks can only be done when the EPC light are on!

I was considering just running the car as usual (sticking to max 70 on the motorway and in the 1st lane so I can get on the hard shoulder if needed - I have full RAC membership so this would cover me somewhat).

Please help!

Defcon5 · 24 Apr 2008 at 21:43

EPC is electronic pedal control. Id change the coil pack first

Firestar_3x · 24 Apr 2008 at 21:44

I've got a 1.8T and i've recently had the EPC / ABS & ESP light come on, its a sensor issue loged by the throttle body.

EPC stands for Electronic Pedal Control, basically its a motor in the Throttle Body instead of a cable.

Clear the fault codes, either disconnect the battery for 20 mins or get someone with Vagcom to do it.

Mine poped up by driving in 3rd dropping it to second and booting it.

A coil pack issue is easy to identify, he would have issues getting up to 80mph.

MagicBoy · 24 Apr 2008 at 21:49

Which engine?

g60dubster · 24 Apr 2008 at 21:50

The best bet is to get it scanned. Faults stay in the memory until erased, so even if it's intermittent it'll show up.
With Vag-com, every error is assigned a code, you can then use the Ross-Tech Wiki to look up the common faults and solutions to it.

As a wildcard, if this is a B5 chassis A4 it could be water getting in past the ECU box seals and dripping onto the electronic throttle pedal...... it's pretty common if the scuttle drain plugs are blocked up with crud.

aftershxck · 24 Apr 2008 at 21:50

Defcon5 said:
EPC is electronic pedal control. Id change the coil pack first

I see - thanks, but I really want to make sure I know what it is before replacing part x first, then part y second, then part z third (yes, I finally realise the value of money now that I work

).

Firestar_3x said:
I've got a 1.8T and i've recently had the EPC / ABS & ESP light come on, its a sensor issue loged by the throttle body.

EPC stands for Electronic Pedal Control, basically its a motor in the Throttle Body instead of a cable.

Clear the fault codes, either disconnect the battery for 20 mins or get someone with Vagcom to do it.

Mine poped up by driving in 3rd dropping it to second and booting it.

A coil pack issue is easy to identify, he would have issues getting up to 80mph.

Just to elaborate a little further, the reason I was booting it in 1st/2nd was because on Saturday night I left the cabin light on and had a dead battery come sunday - friend lent me his charger but by that time in the evening I only charged it for 3 hours so thought I'd drive it a round a bit with high revs to make sure I had enough power for work on Monday!.

Do you mean clear the fault codes - and I attain this by disconnecting the battery for 20 minutes? Or are you suggesting three separate solutions there?

Thanks

aftershxck · 24 Apr 2008 at 21:51

Car info: T reg B5 chassis 1.8 (not turbo)

Edit: will check the oil and water tomorrow just to be certain about that...

Firestar_3x · 24 Apr 2008 at 21:51

g60dubster said:
As a wildcard, if this is a B5 chassis A4 it could be water getting in past the ECU box seals and dripping onto the electronic throttle pedal...... it's pretty common if the scuttle drain plugs are blocked up with crud.

Depending how bad the leak he should also be getting CCM issues....

Firestar_3x · 24 Apr 2008 at 21:52

aftershxck said:
Do you mean clear the fault codes - and I attain this by disconnecting the battery for 20 minutes? Or are you suggesting three separate solutions there?

Thanks

It is possible to clear some fault codes by disconnecting the battery (but not all), worth a shot, check you have the radio code first

aftershxck · 24 Apr 2008 at 21:53

g60dubster said:
The best bet is to get it scanned. Faults stay in the memory until erased, so even if it's intermittent it'll show up.
With Vag-com, every error is assigned a code, you can then use the Ross-Tech Wiki to look up the common faults and solutions to it.

As a wildcard, if this is a B5 chassis A4 it could be water getting in past the ECU box seals and dripping onto the electronic throttle pedal...... it's pretty common if the scuttle drain plugs are blocked up with crud.

Last time the car was serviced/looked at, my mum was told that water was being lost from the car (I don't know how) so that would have be topped up more than usual, I guess this could be a link (or not?)

Edit: also, thanks for confirming the faults are logged in memory until erased, if the problem is intermittent - guess my next step at least is to get the fault codes checked!

Thanks

Firestar_3x · 24 Apr 2008 at 21:58

Yep the fault codes can be read at any time, the fault doesn't have to be happening when they read the codes

g60dubster · 24 Apr 2008 at 22:13

aftershxck said:
Last time the car was serviced/looked at, my mum was told that water was being lost from the car (I don't know how) so that would have be topped up more than usual, I guess this could be a link (or not?)

Edit: also, thanks for confirming the faults are logged in memory until erased, if the problem is intermittent - guess my next step at least is to get the fault codes checked!

Thanks

Nah, water as in rainwater building up in the scuttle area as it has nowhere to go if the drain plugs are blocked up. Can get high enough to come into the passenger cell through the ECU seals or the airbox for the heater system.

This porblem is common to all A4/A6/passats of that age/model

How-to:

http://www.weirdlittlebiscuit.com/passat/leak/