Blue temp sender

[matthg40]

I've just took the plug off the blue temp sender to adjust something and whilst pulling the plug off it made no difference to the engine tone or general running.now I no my revs used to drop when taking the plug off the sender so why isn't it doin anything and could this be causing my running problem many thanks matt

[G40supercharged]

Could be your problem. Your other post said the car stalled below 1000rpm. The ECU keeps the idle stable by adjusting the timing. It doesn't do this in 'service mode' when the blue temperature sensor is unplugged, so it sounds like it can't see the temperature sensor. I would get a new sensor anyway. If that doesn't help check the wiring to the connector in case there is a break in it.

You can check it by adjusting the idle screw on the throttle body to increase idle speed. Reconnect the blue sensor and idle speed should drop as ECU takes over. 

[matthg40]

Ah thanks for that mate that makes sense will check and get a new sensor

[matthg40]

I found 3 spare temp senders I had and I've tried them and it's made no difference I've ordered a new one but I can't understand why it doesn't make no difference when unplugged plus I've redone the wiring on the plug

[hayesey]

it's generally a sign that the ECU is not happy.  Unplugging the blue temp sensor while the engine is running tells the ECU to go into service mode (so it stops messing with ignition timing so you can set it and the idle speed), but if there is a problem then the ECU wont do it.  It's not necessarily the blue sensor itself that is at fault.   It can be any sensor (or sensors) being faulty somewhere, wiring to any sensor (or sensors) being broken, low voltage, bad earths, faulty ECU, dodgy chip, etc...etc...

There are literally 101 things it could be.  Best bet is to read the diagnosis posts in the FAQ sections, then read the vag-com/vwtool one and get hold of a vag-com lead and a multimeter and start testing things.

Failing this, take it to an automotive electrician and pay him lots of money.

[hayesey]

I spent ages trying to diagnose a general running issue on mine (revs not changing when the blue sensor was unplugged then).  Even as far as checking resistance in every wire of the wiring loom.  In the end turned out to be a faulty ECU and swapping it for a new one was the only fix.

[matthg40]

Thanks for that mate I was hoping to they and fix this myself as I know electricians are pricey.as for the fault reader I do not have the diagnostic wires for some reason and that's a worry as I don't quite know me next move

[hayesey]

there should be a post in the FAQ section about adding your own diagnostic wire if it's not there.  Have you looked at the FAQs?