§torm

Hi all,

So I parked my S4 up for the winter back in September, and all was well. I fired her up, and took her out for a drive at the weekend, and on first start, it was immediately high idling around 1700-1800rpm. I left her to warm up for a bit and it dropped slightly but only down to about 1500rpm and no more.

I can also feel her pulling waaay more than normal when shifting into Drive, or Reverse, so she's not running quite right, although when i do drive it, she seems to drive just fine (no misfire etc), unless i come to a stop, and then she doesn't idle properly again.

Obviously something has happened whilst standing. Can anyone suggest likely cause and fix for this, or what to check etc?

Thanks for any advice!

Adk46

I know only enough to suggest that the idle stabilization valve is implicated. It is a spool valve, which might get sticky when ... idle. Some carb cleaner sprayed down a particular hose may free it - it is unreachable without removing the intake manifold.

Someone with more experience will chime in with the exact procedure, but take heart.

The hard shifting is probably just from the high idle.

giddyupp

sounds like it may be your ISV (idle control valve) - that can get stuck. try actuating the accelerator cable by hand, you should here a click almost immediately it moves away from the stop. it should click in both directions as the cable moves away and back to idle. If you do not hear the click, its possible that its stuck. before buying a new one, you can try squirting WD40 down the vacuum hose that goes into it. I believe it is recommended to squirt for approx. 30 seconds. (i.e. quite a lot)

FredR

At 1500 rpm you are not too far away from the stall speed of the torque converter [2k rpm] so no surprises about the fact that it is "pulling".

There is no logical reason why something should have failed mechanically over the last few months if it has just been sat there- the usual suspect for a high idle is a broken/cracked line somewhere in the intake system- some of this plumbing can be seen under the bonnet but the part of the system under the inlet manifold is difficult to see directly. You can try to listen and see if you can hear any unusual hissing noises. Not the ind of thing one might expect given it was sat there doing nothing but...?

Not sure if a temp 2 sensor failure can cause something like this- this sensor has a variable resistance output that basically tells the control system the operating temperature and thus it adjusts the speed/fuel mix according running faster and richer when colder. Is it difficult to start either when cold or when warm?

This does not sound like an LH failure but then strange things can also happen with this unit- has John Speake checked your LH unit at all recently? - is it the original unit?

Just noted the comments on the ISV- if the engine speed is hunting that would be more likely to be the ISV as the computer tries to apply more signal when the rpm's do not modulate as it expects. If the ISV is not working at all it still has a static gap that approximates to the required opening when the engine is warm but that does not cause the motor to race in my experience- just a bit funny until things warm up and you have to gas it a bit to compensate. On the other hand if the ISV shuttle has stuck [jammed] open the chaps have this covered but not sure I would like to squirt WD40 in there- if it works then fair enough.


Rgds

Fred

Tom in Austin

prob a large vacuum leak ... check all the vac hoses particularly the ones that connect the ISV under the manifold.

§torm

Thanks for the points so far guys. I will take an investigative look at the weekend!