MASTER_TECH

It's fastened to the top of the gearbox towards the rear, its easier to get from the nearside, there's three plug's there make sure you get the right one.

Dracoro

Oh right, not something I can see from opening the bonnet then!?! A jack/axle stand jobbie then.

m1bjr

My money's on a temperature sensor....
Sounds like its dropping in and out of 'coool runningz' man!

Mark, any other ecu input for water temperature other than the circuit feeding the dash gauge? An intermittent here wont always show on the dash, even digitals, if there is a programmed damping effect.

OP I'll bet (if it's this) that the car doesn't do it when cold, only when stopping hot?

Dracoro

It has only happened when hot. As I say, it hasn't happened often enough to ascertain any real pattern yet. i.e. it mostly runs perfectly well when hot as well.

m1bjr

Its not uncommon to find the sensor that effectively drives the temperature gauges on many cars also inputs water temperature data into the ECU.
This will be used by the ECU to ascertain if the engine is cold, and if it is the fuel enrichment program will be enabled.
Faulty wiring at the sensor or sensor itself (open circuiting) will give you the problems you are seeing once hot as the enrichment program kicks in and stalls a hot engine from then being too rich.
Obviously it won't be an issue if cold as the fault is masked anyhow.
This is a popular fault on VAG motors like earlier A3, A4 and Golfs.
It may not show on the dash temperature indicator as it can happen to fast for the display to react.
The older analogue temp guages as damped, like the fuel gauge so they are easy to read and stable.
It may even be on a totally different sensor to the dash driven as a separate ECU output.
Don't have that depth of knowledge on this car...
As Mark said there are other causes to investigate too.

MB

Hi Steve - yep the ECU does use the coolant temp to compensate for fuelling in its tables, along with intake temps etc.

It sounds like the car isn't going into idle mode when it should, when coming to rest.

A number of things control, and have input into the idle unfortunately - ISCV, Lambda, MAP, TPS.

Forst port of call is thinking what (if anything) has been done to the car lately. Any mods or servicing?

Then check for air leaks as this is the next basic step, then throttle cable etc etc.

It would be helpful if you (Drac) could go through the checks in my thread and post up in logical order what you have looked at.

Ta!

Dracoro

No mods.

No recent servicing.

Have you got a CEL?
NO

The ECU reset!
Will try this next. Waiting for the problem to happen again 1st.

1) Have you just had a service or added a modification to the car?
NO

2) Is the throttle cable taught?
Seems so, half inch or so of play

3) Is the air filter blocked?
NO

4) Is the car using a lot more fuel than normal?
Maybe a little, could be type of driving however. We're talking 26 rather than 28 mpg. that was only on last tank too. I'll fill up on way back tonight to see what mpg the last 120miles has been.

5) Injectors
Relevant in my case?

6) Plugs
Relevant in my case?

7) The MAP sensor...
MAP whack done, no effect.

8) Throttle butterfly / vac line cleaning
Will do but not sure if relevant?

9) Lots of weird CEL faults?
NO CEL and I don't have reader

10)Air leaks...
Not checked but will do.

02 sensor
Not sure how to locate, jack up car job?

TPS & IAT
Not something I can check as don't have equipment

Bibbs

I had this issue .. I took the MAP sensor off and used carb cleaner on it.
I then ran a LOT of carb cleaner through the engine.

Issue went away.

m1bjr

Sticky throttle body to add to the list...
You have no error codes so I doubt it's anything major.

Still sticking a wad on a temp sender

Good luck - annoying but educational and fun!!!

gaddafi

left field but worth checking, if the other usual suspects don't come up trumps:

tightness of battery terminals
battery securely fixed

looseness in either of the above can result in intermittent problems

very occasionally, it can be the alternator