Lumpy tickover dying !!!

[DB S3]

A little background first - driving home a couple of weeks ago and suffered a 'blow out' on the main cooling system pipe from the swan neck into the engine (the one that can easily get rubbed by the fan belt). The weird thing was, the pipe failed on the top side away from any moving parts, bends or joins. I put that down to age - 15 year old pipe going to perish at some stage i guess. Needless to say, I lost the majority of coolant in the system, had a temperature gauge heading north of 100 and shed loads of steam all over the engine bay.

Anyway, having fitted new pipe, I have suddenly developed a 'tick over' problem. Instead of sitting at 1000 rpm nicely, when stationary the revs start to drop. They tend to fall to about 750 , at which level the engine is spluttering and clearly not happy, but they can drop so far the engine will just stall itself altogether.

When driving along, the car is juddery (more so than usual !). Problem seems no different wether engine is warm or cold.

Have lined up some suspects - fuel pump on it's way out; throttle pot gone; air intake valve playing up.

From reading this forum, i decided to disconnect the throttle pot. Hey presto - engine ticking over at 1000, or sometimes marginally below, and no spluttering or choking.

Which leads me to my three questions -

1. Where is the best place to source a new TP ? And how much would you expect to pay ?

2. I have only had the car in the garage with the TP disconnected. Is it ok to drive around otherwise ?

3. If new TP fixes problem, would you conclude all is well again or could the blow out have impacted other things that may give similar symptoms ?

Any thoughts gratefully appreciated.

Thanks

David

[doddze]

this should help

www.pistonheads.co.uk/gassing/topic.asp?t=204183&f=11&h=0

[DB S3]

doddze

thanks for this mate - exactly what i was looking for.

will give tune parts a call on monday, in the meantime it looks like i'm fine to drive around as per normal (with engine running rich).

quick question though (forgive me, mechanics is new to me and steep learning curve !) -

did you just replace the bit that's bolted to the engine, or the plug that clips in there ? or both ?

edited to say : also had a look at the tune parts website, my tp looks nothing like the one in the photo - did yours ?

>> Edited by DB S3 on Saturday 1st October 20:58

[harry1972m]

I have had the same issues lately and after plugs / leads / dizzy / TP etc etc etc I ended up changing air flow metres which solved it only to then have the TP go on me in a matter of days.
I have a brand new spare TP which I carry around now and if it would help I will post it to you, you can fit it and see if it solves and then post it back to me - saves shelling out circa £45 just to eliminate it.

Mail me thro profile with address if you want to borrow it.
Cheers
Graham

[doddze]

the tp is actually the part bolted to the engine with two small bolts.

It unbolts ... new one in... reconnect clip. The fun may be with which TP you have on at the moment and which you replace it with. You may have to switch the outer two wires...

[numbnuts]

This might sound daft but are you sure you have got all the air out of the cooling system after you refilled it ,it could play havoc with the ecu temp switch which would in turn make it run rich/weak etc.
Just a thought

[mycroft]

Could be air flow meter, next time it runs lumpy and the revs are droping give the AFM a tap on the top, if its sticking the revs will correct them self. It will be obvious if thats the problem.

[harry1972m]

numbnuts,
Can you describe where I can locate the ECU temp switch, I don't think mine is operating properly.
Cheers
Graham

[DB S3]

Guys

Thanks for the suggestions.

Graham - YHM

If it's not the throttle pot, i'll move on to the air flow valve - that also took the brunt of a full out burst of steam !!!

Let you know how i get on.

David

[numbnuts]

harry1972m said:

numbnuts, Can you describe where I can locate the ECU temp switch, I don't think mine is operating properly. Cheers Graham

Hello mate, without looking at your engine its probably a bit difficult to tell you, having said that the switch is usually blue with a two pin multi plug on it probably situated on the inlet manifold.
If you have a multi meter take a resistance ohm reading from cold and then when engine is warm and you should see a difference in the reading,if you have no reading then it is probabley open circuit (knackered)