2 replies to this topic

[jonjo]

IF I stall my 1993 1.3i cooper or start it touching a pedal the revs go up to 3 or 4. If I'm driving while this is happening then revs are at 4, 5 or 6. It revs high more so when I press the clutch to change gear. Sometimes it will just do it anyway!!!!!!! I have to turn it off, take out of gear, give it a minute then re-start and hope it has gone back to normal, not good when I stall in traffic!!! My revs are also erratic, I've had them looked at but its made no difference. Any ideas what could be happening????

[bluedragon]

A quick possibility - you might have a sticky throttle pedal or cable. When the car is in neutral or clutch depressed, and the engine is revving high - put your toe under the throttle pedal and lift upwards (forcing it into the minimum throttle position.)

If this brings the revs down to normal idle, then the problem is somewhere along the pedal to throttle body connection (could be sticky or worn out pedal shaft, a weak or stretched throttle pedal spring, a sticky cable, a cable that's stretched and needs adjustment, or a warped throttle body that is binding when trying to return to closed (minimum) position.) I think the SPI has a throttle body? Not sure.

[spiguy]

A quick possibility - you might have a sticky throttle pedal or cable. When the car is in neutral or clutch depressed, and the engine is revving high - put your toe under the throttle pedal and lift upwards (forcing it into the minimum throttle position.)

If this brings the revs down to normal idle, then the problem is somewhere along the pedal to throttle body connection (could be sticky or worn out pedal shaft, a weak or stretched throttle pedal spring, a sticky cable, a cable that's stretched and needs adjustment, or a warped throttle body that is binding when trying to return to closed (minimum) position.) I think the SPI has a throttle body? Not sure.

most likely to be your stepper motor is failing / failed. Had the exact same problem. For ages, the revs would randomly 'stick' - like your driving along and you notice the car is driving itself, so you dip the clutch and the revs are at maybe 3k. Give it a blip and they go up to 4k, etc etc.. Switch off and maybe it clears.

Eventually though, mine stuck at about 3k and wouldnt come down. Discovered that the stepper motor had failed and so the pin which comes out of it and pushes the throttle had stuck in that position and was holding the throttle on. The problem was caused by broken solder joints on the circuit board inside the stepper motor housing. Re-soldered them and that sorted it.

To check if its your stepper motor, when you switch the car off you should hear it click a few times as it resets. Also, with the ignition in position 2, if you go under the bonnet and operate the throtlle linkage to full throttle and back 5 times, it will reset it position (easier this way sometimes so you can hear it). With the car running, you can also see the pin moving if you blip the throttle (again done from under the bonnet while you look in sideways at the throttle area). It should come out to 'catch' the throttle so that it can take it back down to idle in a controlled way.

If its not working, then apart from checking the connector / cable for anything obvious, you will need to take it apart for a look. Not too hard to do, think its just a case of throttle cable off the ball end at the throttle linkage, then 3 bolts to remove the motor in its housing, then a few screws to take the cover off.

Keep us posted.