engine idea when put into gear

[metal matt]

Gents
I'm looking for a bit of info from anyone with an MX5 build. When I put my car into gear the revs go up from normal ideal. I've done some reading and looking on the MX5 forums and they all point to the clutch switch. I currently don't have one but My question is what have you guys done about yours, fitted the switch or bypassed it.

https://www.flickr.com/photos/124541083@N02/
https://haynes.co.uk/forums/showthread.php?t=13262

[Numplumb]

Hi my mx5 16 does the same when I depress the clutch pedal also when i press
The brake pedal I have the clutch switch fitted
Regards Mick.

[RichardH]

interesting to know the outcome of this, im starting on my loom shortly and was intending to bypass the clutch switch, seems it may be required?

[RichardH]

reading the saturn plans it says the switch make the engine take more fuel when the clutch is pressed therefore if bypassed it will overfuel all the time.

[metal matt]

I haven't had a chance to have a look yet but reading through things there is 2 switches on the clutch. The first is for (push the clutch in to start). I found out about this one when trying to start my engine for the first time.
The second switch is the clutch switch, which I believe from reading and looking on my wiring diagram go's to the cruse control (push clutch in turns off) if I'm right.

So my symptoms are when I put it into gear the revs go up. Reading about this it is not picking up on the Switch so the ESU is compensating for it thinking it is going to stall I think.

I did also read something about it over fuelling when they don't work.

I will try to bypass it to start with to see iv the revs change then if they don't I will have to try and squeeze down into the foot well and try and fit this switch. :eek:



https://www.flickr.com/photos/124541083@N02/
https://haynes.co.uk/forums/showthread.php?t=13262

[flyerncle]

Not had much to do with MX 5 but most engines that have sensors on to lift the revs when loaded ie power steering /ac etc either put air into the manifold or move the throttle body.

[metal matt]

Found this and a good bit of reading on the switches

http://forum.miata.net/vb/showthread.php?t=282088&page=6



https://www.flickr.com/photos/124541083@N02/
https://haynes.co.uk/forums/showthread.php?t=13262

[Numplumb]

Not had much to do with MX 5 but most engines that have sensors on to lift the revs when loaded ie power steering /ac etc either put air into the manifold or move the throttle body.

On mine the revs go up slightly when I put on the headlights

[garyt]

hi , now its running again went and tried mine, in neutral standing still it idles fine, clutch in still idles fine, put it in gear and without touching the throttle the revs rise.... not alarmingly enough to notice and as soon as I go to move its fine.
Its almost like an anti stall if there is such a thing. Its certainly not something for me to worry about... yet

[garyt]

mmmmmm
thinking about this . if sticking the clutch in makes no difference UNTILL its put in gear then it cant be a clutch switch as this would only see clutch in or clutch out . so there must be a sensor in the box as this is the only way any sort of signal can be sent to the ecu. as with the clutch in and no pressure ont throttle there is no other signal sent.
yes switching something on would cause a rev increase because you are putting a load electrical / mechanical on the engine so for example lights on = more currant drawn so revs rise to supply more alternator speed etc,

methinks some searching is in order mmmmmm

[garyt]

aha there IS a "neutral" switch / sensor on the gearbox violet / black wiring. along with the reverse switch and speed sensor
so this must be the culprit. sorry short of going outside and disconnecting it and seeing what happens... but it must sense when the car is NOT in neutral ie. when its put in gear, and sends a signal to the ecu = revs rise

[garyt]

from more learned people than me on mx5nutz ;-

It stops the ISCV from fighting against engine braking unless you are in neutral or have the clutch depressed.
Idle speed stabilisation in the ECU depends on several inputs (clutch, neutral, sidelights, air-con, blower motor, idle). There is a Switch Monitor diagnostic mode built into the ECU


The idle circuit is live in gear with no throttle so that the car doesn't stall and allow you to trickle in traffic

now how you stop it doing its thing I don't know :)

[metal matt]

So whiles it the garage today I had I little fiddle with this. So my symptoms are when the car is running it is ticking over nicley. I can push the clutch in and out with no change to the engine Revs. When I put it into gear the revs go up by about 300-400RPM. So I found the plug for the clutch switch and had a play I connected it up to earth and when I put it into gear the revs do not change so happy days. The thing is I am now going to have to find a permanent fix for it. Options are leave it connected up to earth and see if I get a code on the ECU or by a switch and try and fit it to the clutch. Or myby something else:confused: .

https://haynes.co.uk/forums/showthread.php?t=13262
https://www.flickr.com/photos/124541083@N02/

[garyt]

hi glad you found it I may try disconnecting the neutral wire and see if the same result... but its buried.... so we will see .
as far as I can work out both instigate the icvs (idle control valve system) which is basically an anti stall via the ecu.

[Numplumb]

The neutral switch and the clutch switch and cruise control are spliced together in the loom and go to the ecu.
I think the clutch switch is a push to break switch, not sure about neutral switch but probably is the same, the other side of both switches go to ground so they are holding something low until you change there state by pushing the clutch or putting it in gear.
I would think the clutch switch could be done away with but not the neutral switch.

Google the Miata King Mike he has a you tube video about the neutral switch jamming the gearbox in reverse.

[garyt]

just watched the video you recommend and it highlights a problem with the selector jumping inside the box, thus sticking in reverse, sorted by poking in the reverse switch hole.
he also highlights the other switch "neutral" and explains it is used for idle control and emissions via the ecu
. so with the other searching Ive done , yes your right that the different switches trigger the same icvs in the ecu. I guess I need to try it and see, my clutch switches are bypassed which only leaves bme with the neutral switch so when I push the clutch in = no change to the idle speed, however as the OP when I then put it into gear there is an approx. 300 rpm increase take it out and the revs fall back to a steady idle.
I guess it is a try and see one as no other car I have had has had this and they have all driven fine