Engine Revving By Itself!! St2

[JD_ST215 1]

**INFORMATION/HELP NEEDED**

I have a problem with my ST2. When changing gear/dipping the clutch, usually in the higher gears 4/5/6 the engine revs by itself without me touching the accelerator. the revs climb to a certain point which is always exactly matched with the speed of a gear 1 or 2 below the one I'm currently in.

its been in the garage 3 times and they say theres no fault code. so I need to know what this could be because my nect port of call is an independent inspection but im not paying for one if they arent going to find a fault code either, because then I cant claim the costs back. no matter how much people tell me its normal, at the end of the day no car should rev by itself and ive been in other STs and they dont do it.

can anyone throw some ideas at me because I need to get some info together before I take it further. cheers

[Dan62 78]

A bad clutch pedal position switch maybe ?

[Andy.B1971 186]

A sticking throttle flap/idle control valve all in one these days on the newer cars, in need of live data I think via some adequate diagnostic equipment :D

[leicsguyuk 1]

I had this happen on diesel Golf a few years ago, It was sucking up oil that had found its way into the Intercooler, I took the intercooler off cleaned the oil out, it never happened again.

[Andy.B1971 186]

if oil on a diesel is over filled the engine will hunt up and down as the extra oil is used as fuel.

too much oil in a modern petrol car can cause all sorts of nasty things to happen.

like I say I think you need the live data to be read for values . :D

[JD_ST215 1]

thanks for all the comments folks, its a bit of ammunition to go back to arnold clark with at least!

I've ordered myself an OBD2 reader so I can get soke readouts and see what's going on.

any more info welcomed obviously. the more ideas about what this is the better...

[jeebowhite 5,104]

definately worth checking the oil level and drain it as necessary.

how bady is it hunting? are we talking minor fluctuations, or are we talking about a rev needle swinging from one side of the tree to the other?

[JD_ST215 1]

I honestly dont think it will be oil. it seems too clinical and predictable for that.

when the engine revs,it revs to a very particular point, because the revs are trying to match the gear below the one im in. its almost as if its trying to anticipate me downshifting even though im shifting up

[jeebowhite 5,104]

does the hunting occur whilst idle?

[JD_ST215 1]

no, only when im travelling along, its usually as im shifting from 4th-5th and 5th-6th.

say for example im doing 35 in 4th @ 1700rpm roughly... I dip the clutch to change into 5th gear, and instead of dropping, the revs climb to say... 3000 or around that, as if anticipating that im shifting down and not up.

ive tested this, and instead of shifting into 5th like I intended, I went down a gear, and the revs were PERFECTLY matched with 3rd gear. seamless change. its like the synchromesh is broken and its just picking a random gear to sync....

but theres no error codes showing on the ecu? surely this isnt normal behaviour for a engine.

[JD_ST215 1]

in some cases it has tried to match 2nd gear when ive been in 5th... its revved up to about 4500 . theres no way anybody can tell me that's supposed to happen

[jeebowhite 5,104]

hmmmmm, very perculiar, I beginning to wonder if a software update is necessary. It seems like its doing what an auto would, as the autos are more inclined to try to match revs....

If that fails, I would say you probably need to check the likes of the MAF sensor is clean, and a basic service such as air filter may be in order?