embarrassing uncontable reving & swaping exhaust?

[tommy2decks]

when i pull up at junctions and lights sometimes my 88 8 valve revs constantly to 2,000 then nearly to 0 then back again. it stops (sometimes) when i switch off lights, heater, or unneeded electrical things wipers etc. but sometimes this is not possible as there is nothing switched on, any ideas what is causing this? its become embarrassing as 'old dear's' run across the road in fear then give me the evils, and mopeds think that i want to race them....as if (they only clog my air filter)

any ideas ?

also i was thinking of removing the straight section (stits under the tunnel)from my exhaust and replacing it with a straight through pipe of larger diameter, would this be detrimental to my engine?, i allready have a Ashley middle and back box off i presume a 16v as the bore diameter is bigger, would noise be the only issue?

[Gambit]

change the blue temp sensor. there is a guide in the maintenace section i think.

also, changing the exhaust to a larger bore and going to a straight through will usually reduce torque but show slight increase in top end bhp

therefore your car will feel slower in general day-to-day driving

and it will be LOUD i would say unbearably loud.

its been proven that OE VAG systems are very well flowed exhaust systems already and are in no way restrictive unless ur running big power

[tommy2decks]

thanks
will give the sensor swap ago, and leave the exhaust as it is, mabe swap the manifold and down pipe at some time in the future.

[tommy2decks]

bought a new sensor, £27.00 from the local dealer, fitted it amd no change.........

[Gambit]

need to work back then from the sensor along wiring etc checking for breaks/bad earths

[j_s]

I had this problem and still do but to a much lesser degree.
I have changed the blue sensor.
I have changed (tried 4) the idle stabilisation valve (isv) which went a long way to almost fixing it
I have replaced other bits and pieces as well
Checked the co and fueling which helped a little bit
Check for vaccum leaks as well by fiddling with the hoses near the isv

[rubjonny]

sounds to me like the idle switch, make sure it clicks with the throttle is closed and the wiring to the switches isn't broken.

The idle switch is underneath the throttle body & you have to take the inlet boot off to reach it, its fiddly to adjust but it needs to be set so it clicks just as the throttle is closed.  Make sure the throttle goers right up to the stop as well, if the throttle cable is too tight it can give you these symptoms as well.