Clutch Switch..... what does it do??

[GingerMagic]

Hi, new forum user here - just been reading posts and I am surprised how complicated the Hdi is.

Quick question - when I bought my 52 plate Hdi90 a few years ago, it was very lame indeed. My friendly Hdi mechanic looked under the bonnet and took up the slack in the throttle cable ( I was only ever using half throttle! ) which made quite a difference.

However, when I rested my foot ever so lightly on the clutch pedal - maybe an inch or so - the car picked up and almost performed like it should. Upon inspection I found the clutch switch and simply unplugged it. Now all is okay with the car, albeit still juddery at 1500 rpm, but I am not sure what the switch does and should I keep it plugged in but loose the perkiness of the engine??

MPG is varied from 38 to 45, depending on driving style, and up to 55 on a gentle run. Can this be improved as I am a phenominal tight arse...

I have found a few ideas here which have helped other aspects of my trusty steed, so thanks to all contributors. I am sure there will be many more questions.

[lozz]

Clutch switch, the ecu cuts the fuel when you dip the clutch,
its also there as part of some cruise control set ups,

[GingerMagic]

Okay, thanks. Should I replace it with a new one so I can plug the lead back in? As it runs better unplugged does this mean its faulty?
I guess no damage is being done but I suppose that a working one should be there. ...

[Doggy]

I understand it's there to disengage cruise control when you dip the clutch, to avoid over-revving the engine. As a 'side issue', ecu software programmers seem to have adopted the notion that if the clutch is pressed, the engine isn't 'driving' the car so fuel should be limited, cos you're just blipping the throttle for the hell of it........

This could explain lethargic performance if the ecu 'thinks' the clutch is pressed, but doesn't really explain the behaviour you and others have described, where it goes better with the clutch pressed a bit, (unless it's simply a switch adjustment problem)?

[Bailes1992]

My 406 also does this.
I have plugged in PP2000 and it didn't even have the clutch switch switched on

Rich's also does this too.

[Bailes1992]

Just had a look at my clutch switch and unplugged it myself.
Looking at it, there is about an inch adjustment on the clutch switch. If it works I will wind the clutch switch out a little.

[Bailes1992]

What the holy hell

Throttle is much more progressive, the 'inch' flat spot at the start of the throttle has totally dissapeered and the car seems to go a little bit better

[GingerMagic]

I just tried to adjust my clutch switch so I can plug it back in and it just spins round and round.....
I did also spot that it is attached to another wire that plugs in to a black plug behind centre console, that is still plugged in.
If I can remove the clutch switch then I will replace it and see what happens. Hacksaw might do it..!
Glad this post has made other 406s go better......

[grasmere59]

I think the switch is just clipped in when you push it in the hole,when i bought my car the switch was just dangling on the wire and i just pushed it back in the hole,i thought i had pushed it to far in so i just pulled it back a couple of notches,funnily enough my car went better when the switch was in place and not when it was dangling on the wire (eg dipped clutch),when back in position the cruise control started working again.

[mjb]

Might have to have a peek in the estate's footwell now!!!

[Bailes1992]

Is your 90 a siemens?

This seems to only effect siemens cars.

[rwb]

Here it is, seen through the flap underneath the steering wheel.


And close-up:


Noticeable effects:
(1) The speeding up when clutch pressed lightly thing has gone.
(2) Revs do not fall as quickly between changing gears (in certain situations). I found this made matching revs and thus changing gear smoothly to be easier.

[rwb]

Questions:
(A) What is it supposed to do? Does it provide additional features for cars with cruise?
(B) Does it exist on other models? Does it depend on diesel/petrol? Pre- part- or full-MUX?

[GingerMagic]

The story so far, unplugged clutch pedal switch 2 years ago to improve performance and perkiness, which worked a treat. This made the car a bit stuttery changing gear and sometimes stalled on cold mornings but learned to live with it and changed my driving style to suit.
After reading the responses to my original post, I have plugged it back in but removed the switch from the pedal ( just pulled it out ) so it hangs free. This way the ECU knows it is there and working so goes well, but the little button on the switch is not pressed in when driving so the car performs better and has smoother gear changes.... Everyones a winner!!
If you don't have cruise control, it seems that pulling this switch from the pedal but keeping it plugged in, improves driveability and responsiveness. Not sure Peugeot would agree though.
Mine is a Siemens model, by the way. 2002 Hdi 90 GLX Estate, in a state. 172,000 miles so there was nothing left to loose....

[GingerMagic]

Ignore that last post, unplugged it again but pushed it back in place as this was the best alrounder for performance and smooth gearchange....