fast idle, engine over-rev on start and dodgy temp gauge !

[scottj]

Please help,

We have a model year 2000 alhambra 1.9 Tdi, (110bhp I think!) and everytime after starting the engine, the glow plug dashboard light stays lit for about 10 to 15 secs and then when I turn the ignition, the car revs all by it's own up to about 2500rpm (really load and embarrassing) and then settles back into a fast idle, at 1000rpm. This happens when the engine is warm, ie, first thing in the morning, car starts as normal, if we then park up and then restart the car soon after stopping, the above symptoms occurr. It's as if the ecu is not getting the message that the engine is already warm and thus too much fuel must be being injected and causes the over-revs.

Also, our coolant temp gauge has not worked correctly for years now, ie most of the time it does not move, but very rarely it does move up and shows a reading, then the needle drops down to zero degrees C again !

I suspect the coolant temperature sender has failed, but does anyone agree? also, where is this sensor on the engine please?

 

[fredt]

possible the one in the coolant hose on the engine? the failure of this sensor has been known to cause odd running and high tick over for the reasons you state

 

[goble]

coolant light is flashing due to a fault in the system which i suspect is down to start advance on injectors/ecu which could be but havent seen it before causing it a coolant temp sensor fault

 

[fredt]

surely the glow plug light stays on as the ecu is getting a false signal that the engine is cold and hence their operation is call for, the over reving and high tick over again due to the ecu getting the wrong info and over fueling to aid the sopposed cold start?

 

[goble]

nope

 

[fredt]

so why does the vehicle start fine when it's cold and only play up when the engine is warm? and where does the op say that the coolant light is flashing?

 

[scottj]

There are NO warning lights on the dash when this fault occurs.

I have purchased a new coolant temp sender from seat, it comes with a rubber O ring and a plastic wishbone type clip. Does any know where this fits on the car? There is a fat pipe (approx 30mm dia) coming from ( I think) the coolant expansion tank in the rear right hand side of the engine bay as I look at the engine. This pipe terminates onto some metal device on the upper right hand side of the engine block, with lots of smaller diameter pipes ( say 10mm ) connecting to it. it is held in place by the typical metal spring compression clip, pliers requirred to open the clip!.

I think I will unclip this pipe and see if the sender is connected
to the end of it.

All I really wanted from you guys is confirmation of where the sender is connected to on the engine !!

 

[fredt]

the sensor is locate in a hose not in the end of a hose, it has to be in the flow not in a stagnant section on hose, IIRC it's top hose from the rad?
not having ever had the misfortune of owning a TDI I think 'the metal device on the upper right hand side of the engine block' your on about maybe the oil cooler?

just a though take a look on http://www.vagcat.com/ and see ifyou can see the part you have?