12 replies to this topic

[heathcliffe]

I have a 94 cooper and its recently started to rev on its own when i take it out of gear ( even whilst changing gears) after about 30 mins+ driving. It can reach up 5000 if iv been driving a while, traffic lights are quite scary and you get some really funny looks !! Stops doiing it if i turn the engine off and on but then starts again aroun 10-30 mins later.

I thought it may be the throttle cable getting stuck but it seems fine and if it was that wouldn't it be doing it all the time and not just after 30 mins.


Thanks in advance if anyone can help!

[nicksuth]

Have you touched the Throttle Sensor, Throttle Cable Connection or Throttle Body Spindle?

I recently fitted new Throttle Body with TP Sensor and a K&N Cone Filter which involves fitting a new Throttle Cable Bracket and had similar problems.

Throttle Body instructions were to make sure Throttle Cable was adjsuted correctly (letting Butterfly close completely), then switch ignition to position 2, press pedal 5 x times to bottom, then turn off and wait 15 seconds. This should reset (zero) the TP Sensor.

It appears to work for me, although does occaisionally sit at 1500rpm for a second before returning to normal?

[Sprocket]

Have you touched the Throttle Sensor, Throttle Cable Connection or Throttle Body Spindle?

I recently fitted new Throttle Body with TP Sensor and a K&N Cone Filter which involves fitting a new Throttle Cable Bracket and had similar problems.

Throttle Body instructions were to make sure Throttle Cable was adjsuted correctly (letting Butterfly close completely), then switch ignition to position 2, press pedal 5 x times to bottom, then turn off and wait 15 seconds. This should reset (zero) the TP Sensor.

It appears to work for me, although does occaisionally sit at 1500rpm for a second before returning to normal?

Dude, are you describing an MPi?

[heathcliffe]

Haven't touched either but i will check that thanks

[Sprocket]

I have a 94 cooper and its recently started to rev on its own when i take it out of gear ( even whilst changing gears) after about 30 mins+ driving. It can reach up 5000 if iv been driving a while, traffic lights are quite scary and you get some really funny looks !! Stops doiing it if i turn the engine off and on but then starts again aroun 10-30 mins later.

I thought it may be the throttle cable getting stuck but it seems fine and if it was that wouldn't it be doing it all the time and not just after 30 mins.


Thanks in advance if anyone can help!

This has something to do with the stepper motor, im sure. It might be that one of the windings in the motor itself may be playing up. what happens then is the stepper gets lost. Turning off and back on again resets the stepper, where it takes another 10 minuits driving to get totaly lost again.

I suggest a diagnostic test for this one, but before you do, remove the stepper motor from its housing, and re solder the wire connections on the motor itself. I have found in the past one or two dry joints which could cause this problem.

Other than this, make sure the throttle cable is correctly adjusted. It is described in the haynes manual how to do this, and you may well find several toics describing it also.

One thing to point out. If the small screw that the stepper mottow bears against on the throttle linkage, has been adjusted, you will need a diagnostic unit to reset the correct stepper position at idle. This is something else that can cause high idle speeds but not for the reasons most think.

[nicksuth]

oops forget everything I said.

[Sprocket]

Oh, there are no magic sequencies to reset anything on the SPi. I cannot comment on the MPi but there is nothing in the workshop manual that states these 'reset' methods, so I would be more inclined to think that any magic procedure is simply a placebo.

[heathcliffe]

oops forget everything I said.

No Worries

[heathcliffe]

This has something to do with the stepper motor, im sure. It might be that one of the windings in the motor itself may be playing up. what happens then is the stepper gets lost. Turning off and back on again resets the stepper, where it takes another 10 minuits driving to get totaly lost again.

I suggest a diagnostic test for this one, but before you do, remove the stepper motor from its housing, and re solder the wire connections on the motor itself. I have found in the past one or two dry joints which could cause this problem.

Other than this, make sure the throttle cable is correctly adjusted. It is described in the haynes manual how to do this, and you may well find several toics describing it also.

One thing to point out. If the small screw that the stepper mottow bears against on the throttle linkage, has been adjusted, you will need a diagnostic unit to reset the correct stepper position at idle. This is something else that can cause high idle speeds but not for the reasons most think.
[/quote]

Righty o then i have some stuff to do tommorrow, thanks alot for that mate i hope it sorts it been driving me crazy.

Is there stuff in the haynes about the stepper motor too? will look at it when i get off this.

Cheers

[heathcliffe]

Looked in haynes i take it its a full day job with the 3 page spread?

[Sprocket]

The haynes doesnt describe much about the stepper.

So

remove the air cleaner, remove the screws holding the injector housing to the throttle boddy, loosen the fuel pipe clamp to the right of the throttle body, move the injector housing out of the way with the fuel pipes still attached. now you can remopve the screws on the top of the stepper motor housing. This is the bit where the throttle linkage is attached on top. Obviously the throttle linkage needs to be moved out of the way also. leave the three large philips head screws alone, the stepper motor and the top of the housing will all come out in one go

[heathcliffe]

Ahh you get even better dude thanks. the haynes always seems to be very vague when it comes to injection models iv always found.

you think its probably water damage then on some components because iv recently had a flip front put on and i wasn't very pleased with the work, it seems a little half arsed. iv had lots of problems mostly electricle since the bad weather started so im thinking it could be the body work letting in too much water???

[heathcliffe]

thought i'd try the cable out first seen as it was easier to get to, it was abit loose so i tightened it up and adjusted it according to the haynes and it seems to have done the trick. Just been out for half hour and it idling at like 800-900.
I'm gonna keep an eye out on it for abit to make sure.

Thanks again!!