18 replies to this topic

[DaveRob]

As I understand it....the throttle switch tells the ECU that the pedal has been pressed and that the ECU should recognise that the engine is now NOT idling..... Ergo...by disconnecting you should have MORE problems and not less, ( unless the switch is driven to open when the pedal is pressed). Personally I dont know if that switch is normally closed or normally open without the pedal pressed......sounds like it closd when idle and open when you put your foot down. By disconnecting the pedal Im guessing that maybe your engine idles a bit higher than normal...... but that is just a guess. If you have had the problem from the time you bought the car then just out of interest...what is the part number of the ECU that you have on the engine???.... Is it a 2 plug or a 1 plug...... Be aware that if you do a search you will find that Sprocket advised this back late last year and Im not gonna argue with DA MANNNnnnnnnnnnnnn

Can of worms mate!

If you have the 1992 cooper ECU and no throttle switch then the problem is most likely the throttle switch. Does it pop and fart as well?

Be warned, if the cat is still fitted, you WILL melt it, then the problems get worse as the exhaust is restricted.

I cant for the life of me remember if the throttle switch is normaly open or normaly closed, by the sounds of it its normaly open, so when you press the accelerator the switch is closed.


I too think you are dicing with the unknown by running it without the plug connected....to be honest....if you cleared the fault with the plug connected THEN AFTER PUTTING IT ALL BACK TOGETHER...the fault returned, I would start looking for shorted wires or something screwing up the switch.... The swich performs a function....its ment to be their...It tells the ECU how to adjust the fueling and when the engine comes out of idle...UNLESS SOMEONE FITTED A LATER ECU which doesnt have the switch in circuit...... I havent got a modle with the switch.... I advice by doing research and following the cuircuits I have and the collection of information I have on the SPi and the Rover MEMS, ( which grows daily cause I look and look and ask and ask...lol)..... Your problem is switch related... I think we can 90% say that now.....BUT.... dont run it disconnected UNLESS you have the right ECU....... At this point you need to advise

What ECU part number do you have....should start with MNE.....
2 plug or 1 plug ECU
What Engine number do you have......
exact model and best date of manufacture you can tell us
what mods have been done to the engine

And whill we are digesting this....go and look under the dash till you find where all the switch wires go..... and while your at it can you please advis eif the throttle switch is open WHEN THE PEDAL IS LEFT ALONE or iff its closed.....use a multimeter

Sorry if this sounds like a teacher...its not meant to... but you would be suprised at the amount of people who post a question....then dont include some vital spark of info that is critical to the diagnosis.....prvide as much detail as possible...and if you dont know how much to post then Ill start a new thread so people know where to start when they ask.

Thanks for listening, hope this helps

DaveRob

[Git]

Hi DaveRob,
Must say, you know your onions! I'm well impressed.
I don't know the answers to half your questions but I'll do my best to find them (at work at the mo)
Yes, the engine did idle a little higher for a bit, then died down to a more normal level.
Whilst I was fiddling with the wires and pumping the throttle there was the odd 'Pop and Fart'
I don't have a 'cat' fitted. (I thought I did, so I bought a link pipe to go in the cats place for more oomph. Just before the MOT I thought 'I know, I'll get this pipe fitted, I had a look under the car... what a spanner... no cat... anybody want one??) by the way emissions were fine for MOT.
I've got a guy that knows loads about minis, he did the work on Git for the MOT and the relay thing, 'Titch' is his name (Grasstrack racing is his bag at the moment, used to do a lot of drag racing... fantastic guy) well, he's coming over in the morning, I'll ask him if he can test wether the switch is open or closed etc. I'll try and find out the rest as I get the chance.. not working this weekend, have a look then,
Cheers.
Lee

[DaveRob]

OK... found a bit of time to make a reasoned and researched reply...

The switch fitted to the accellerator on pre 1993 injection minis was their for idle speed recognition and deceleration cut off... and is implemented during Idle condition and engine over run to improve economy and improve emmisions. The conditions for over run...according to the data I have is as follows

1...Throttle closed...in this case when you remove your foot from the accelerator the pedal switch contacts are CLOSED
2...Engine speed above 1500 RPM
3...Coolant temp above 80DegC
4...once engine speed drops below 1500RPM the injector cycle is turned back on

Untill 1993the throttle pedal switch indicated a closed throttle and so this is the way the ECU interpreted Idle condition or deceleration. From 1993 onwards this function was derived from the TPS signal at the throttle body

On pre 1993minis with the pedal mounted idle switch the engine SHOULD cough and f@rt if the engine speed is increased by moving the throttle lever directly ie under the bonnet. This is because the ECU links the idle switch closed condition with the RPM and goes into fuel deceleration cut off mode. Theirfore IT WILL ALSO DO THIS if the switch is fubar OR their is a short to earth from the ECU signal out line to the switch at term 2 on the pedal Theirfore the engine RPM should only be increased by the pedal ON THESE MODELS.....(assuming the swich works and no shorts)

If you disconnect the switch theirfore the ECU goes into a switch fault mode...it will appear to work fine BUT on deceleration YOU WILL BE RUNNING INJECTORS....and so chucking fuel down the bores and over the lambda and your cat...where fitted

The 2 wires on the pedal switch are earth and idle signal

With engine off but IGN onput a digital multimeter neg probe firmly to earth and the pos probe to term 2 on the switch...make sure its not the earth side.

it SHOULD READ zero volts

if it isnt then check the earth wire AND the switch resistance

if it is then by pressing the pedal you should get 5 volts

if its low or non existant check for shorts

if thats ok disconnect the switch connector and check you have 5 volts comming from the signal from the ECU

If you dont then trace the wiring back to the ECU and find the short or break.

Just my thoughts...but this is what I guess might be wrong with your Mini..... and by the way the ECU will have recognsed a switch fault and logged it in its Non volatile mem...so you need someone with an FCR to clear that bit.....it wont affect things if you fix it but might lead to confusion when you first connect a fault code reader later.

Just my thoughts and got me tin hat on if anyone shoots...lol

DaveRob

[Git]

Wow, like I said, 'You know your onions'
Thanks for explaining it in a way I can understand, I'm not the most technical minded bloke... I'll give things a go, and usually, once I've cocked it up beyond all recognition, I get someone in to fix my mistakes.
The plan was to get an old junker to strip down and rebuild, learning (hopefully) on the way so that when Git would go wrong, I'd be able to fix him... tipical he breaks before I can start!!! bl00dy car !!!!
Never sell him though.... tempting... how do you think he got his name... (he was going to be called Angus)
Thank again.
Lee