Drove off to the sports centre tonight - no problems.

Got in the car for the return journey and it was really difficult to start, and when it did it was running really poorly on light throttles. It was OK on bigger throttles, no misfiring but not much power either.

When I hooked up a friends ODBC scanner I got the following:

17972 : Throttle Valve Adjuster - J338 Low Voltage with Basic Setting P1564 Intermittent

17705 : Turbo / Throttle Valve Connection Pressure Loss P1297

16684 : Misfire Recognised P0300

16685 : Cylinder 1 Misfires Detected P0301

16687 : Cylinder 3 Misfires Detected P0303

16686 : Cylinder 2 Misfires Detected P0302

16514 : Bank 1 - Sensor -1 Electrical Problem

There have been other regular problems with the cars perfomance, but am worried that the extra info might actually muddy the waters.

When I cleared the codes, the car suddenly ran perfectly!!!

What the h*ll is going on with this flipping car???

worth checking the engine loom earth wires down by the battery for corrosion first i recon

Earths would be a good place to start, as said above.

High resistance joints can cause all sorts of problems.

The 17705 code means there is a leak between the turbo and the intercooler (sensor on top), could be related to the eary, but I doubt it. Check all the pipes are securely fastened, expecially the one behind the driver side fron wheel. They're famous for breaking!

Thanks. I'll check the connections as best as I can (as suggested).

I'm still confused how reseting fault codes could sort out the poor running - its not like I'd actually made any physical changes!!!

How can this be possible?

I'm still confused how reseting fault codes could sort out the poor running - its not like I'd actually made any physical changes!!!

How can this be possible?

If the car logs a fault code to do with the engine the ECU will adjust the fueling and ignition timing to cope with the fault, so the car is still able to run, it just doesn't run right. If the faulty part (eg. a valve or a pipe) is replaced or repaired the code needs to be cleared so the car goes back to using the values it should be.

So in this case one of two things happened:

1. An electrical problem caused a whole load of spurious signals that the ECU (wrongly) believed and adjusted itself for.

2. Since the signals were nonsense then so too were the adjustments

3. Poor running resulted which was fixed when the ECU was reset.

OR.

1. A induction leak caused a whole load of out of range signals that the ECU adjusted for.

2. The adjustments gave bigger problems than the leak itself.

3. Reseting the ECU wiped the rubbish adjustments and fixed the majority of the running problems

4. The leak must still exist, so driving the car under boost will lead to another set of fault codes.

hmmmmm, its probably the first scenario isn't it?

Probably the first scenario. As the others have said, check the wiring, especially earthing connections

Edited 22 July, 201015 yr by chicken_eyebrow

If those codes don't come back within the next week then don't worry it's sorted, they will soon be back if the fault is there still

Dreaded17705 code usually puts the car into limp mode until you restart the engine or clear the fault. Some of the other codes could of been there for some time. When I bought my VRS a few weeks ago the 1st thing I did when i got it home was hook up vagcom, & there was a huge list of codes, probably the cars entire history in there! Cleared them & none of them came back.

I've had a lot of issues with this car - and have regularly had to clear down the codes. So I think they are all related.

I've just checked the earths. If this is what was meant....

They were all showing virtually zero ohms resistance, but I took em apart and cleaned them up anyways.

So I don't think that that was the problem...

If it is electrical then what else could be the problem?

I've now checked the intercooler pipe in front of the drivers front wheel....

Everything looks OK there too!!!

aaarggghhhh!

Are the codes back yet ??

Noop.

Just been out for a drive in it. Absolutely fine.

I wouldn't start poking around until the light comes back on if ever, but there again I am lazy

Have you had and cleared these codes before ???

I've just found this as I was poking around.

It was hidden under the drivers seat.

The other thing is that the door-open warning light is pretty much always illuminated - when the car has been opened up on the central locking and even when the engine is running.

Snatching at straws now.

Latest theory is that because the door open warning light was flickering on the night the car failed, that some electrical noise from that upset the ECU.

So, I've searched out the cause of the door open warning light problem - and it seems to be the tailgate. When I disconnect this wire, the light goes out.

So I'll replace that switch, but also still would love to know what the wire under the seat was for....

It was probably for the seatbelt warning chime. A lot of people disconnect it so it thinks the seatbelt is plugged in, and therefore doesn't nag you to put it on.

On the last two pics:

Underneath that heatshield pad thingy, is the boost connection which usually comes loose.

A thread shamelessly stoeln from uk-mkiv's My linkhttp://uk-mkivs.net/forums/p/196315/1288037.aspx

It gives a bit of a better idea what I mean.

Might be worth replacing those jubilee clips while you're at it, looks like it'll be a struggle to get them off if they rust any more!