mk3 Golf technical help.

patch

My golf is revving by itself just after startup. I've had the coil and the whole fuel pump assembly changed. Now my mechanic wants to change the ECU -which costs a feckin' fortune.

Anyways, while it's revving up and down on its own, I can hear a rapid clicking, same sound as the indictor relay going on and off, only faster.

I'm thinking there might be a feul pump relay I can replace, before deciding on spending loads of cash.

Does anybody have any ideas? Or know if I'd find a wiring diagram from a Haynes manual online?

Cheers.

kayos

check out the forums on http://www.vage.ie and I am sure someone will point you in the right direction. I really doubt you have to replace your ECU for a rough idle problem...

patch

Cheers for that, I'll check it out.

It's not a rough idle problem, the engine revs up VERY high. If I'm not VERY careful, it floods really badly leaving me stranded.

I had to remove the plugs and burn off the petrol to dry them out.

If I were to turn off the engine while it's playing up, I'm stranded. If I don't turn the key straight away when starting, it's flooded really badly.

As well as that, once it let NO petrol through, which is worse as that's a lot harder to remedy!

Hence I'm hoping tis a faulty relay.

BrianD3

Could be something like a dodgy coolant temperature sensor. The sensor could be giving an artifically low temp reading to the ECU which will then tell the engine to run richer than necessary. Maybe you could mention this to your mechanic ansd see what he says.

BrianD3

kayos

@BrianD3 Yup sounds like that alright I had the same problem on my cupra. The ECU though it was -40 and was litterly just dumping in loads of petrol when trying to start up. If it is this thats causing your problem you should have noticed your temp guage falling below half way when driving or not moving at all. Anyone with VAG Com should be able to see if this is the problem by looking at the correct data blocks. The good news is the sensor is only a cheap wee part to buy. This is also a common enough problem on the VAG cars.

BrianD3

If it is this thats causing your problem you should have noticed your temp guage falling below half way when driving or not moving at all.

Dunno about VW group cars, but on the cars i'm familiar with (renaults) the coolant temp sensor and the temp gauge sensor are two separate devices. So a faulty coolant temp sensor would have no effect on the operation of the temperature gauge, only on the running of the car. Anyhow, I agree with the point about bringing it to a VW dealer who will run some diagnostics on it and should find the problem pretty quickly. Don't know how much dealers charge for running these tests but it'd certainly be chepear than letting his mechanic replace the ECU without knowing for sure whether it was the source of the problem

BrianD3

patch

Thanks guys. Funnily enough, I have noticed the temp gauge hanging back a bit.

It's most likely a sensor somewhere playing up, but it does it when the car is warmed up too.

Thats why I'm trying to get a diagram of the system from a haynes manual.

The guy is going to borrow an ECU from a mate of his and swap them so we can rule it out.

I've seen mention on the net of a fuel pump sensor, so seen as I can clearly hear the relay popping away, I thought I'd switch that first. At least then I could figure which sensor was faulty leading to it, if changing the relay didn't sort it.