revs dying

[bumperblue]

Hi everyone,

Little issue with my S2.Happens hot or cold.

Driving along, come to a situation where you dip the clutch and off the throttle and obviously the revs drop. They drop to 400 and almost immediately you can feel the computer, I guess, immediately pull the revs back to 800. But, there is a noticeable lag in this. It idles fine at a steady 850-900 no problems.

I am assuming what is supposed to happen is the revs should drop to 850 and be held there, not go below to be pulled back.

Any body got any ideas?

Ian

 

[BlackMagic]

Check out the throttle position switch.

 

[alwigley]

DME temp sensor could be giving trouble, caused my early model to not hold the revs, whereas I think the later ECU's have a 'get home' function that keeps the engine running in this eventuality. Disconnect the sensor with the engine running and see if the engine surges as a result, as it can be fiddly to tset the sensor right across the temperature range, and they can give troubles at different points in the range.

 

[sawood12]

As well as checking out the throttle position micro-switch try cleaning out the Idle Stabalisation Valve with a squirt of carb cleaner. Also, not sure if the speed and reference sensor is the same arrangement as it is on the turbo, but try waggling the bracket your speed sensor attaches to. If loose you can nip it up with a socket. Of course it could be your speed sensor on its way out, but best to try other things first just in case.

 

[DivineE]

My bet is on the throttle position sensor. Or air flow meter. Clean the throttle body and the 'barn door' flap inside the AFM to make sure nothing is sticking and I reckon you'll have a free cure[]

 

[sawood12]

AFM is not being used in idle position - assuming that the throttle position microswitch is working of course, but worth checking all the same.

 

[DivineE]

I wondered about it sticking (sealing) shut with dirt for a second when the clutch is depressed and it swings back, then pulling itself open again as the engine sucks through it. Causing a momentary drop in revs. I saw that they can stick shut on an old lux my friend owned once.

 

[peanut]

also check you haven't got a leak somewhere in the vacumn system particularly the hoses either end of the aux air valve

 

[Alexw]

Mine does this, but only for about... 1min after start up. Almost like its about to stall and needs a bit of throttle. I CBA to sort it though as its always gone away before the end of my road.