Stepper Motor?
Discussion
I appreciate this has probably been posted a million times before but the search facililty doesn't appear to be working.
Decided to get the Chim out today for its weekly drive and noticed the idle is different from usual when temp is reading 90+ degrees. The symptoms are that when coming to a standstill at a junction/lights etc and depressing the clutch the revs rise to about 1400rpm then after 5 secs fall to regular idle.
Guessing this is most likely to be the stepper motor but according to the service schedule it was cleaned about a fortnight ago when I took it to Fernhurst. Assuming it was actually cleaned.
Called Fernhurst but all the technicians had gone home.
I've looked at the guide which Davetherave sent me and it looks relatively simple to remove/clean although the photos are so small it isn't totally crystal also not helped by me being mechanically inept and with very limited tools.
Does anyone fancy giving me a hand tomorrow, Saturday 13th, to take it out and give it a clean. Alternatively I'll call Leven and see whether they're open and get a diagnosis of the problem, although I'm guessing they won't be around on a Saturday.
Any help welcomed in exchange for beer tokens!
Decided to get the Chim out today for its weekly drive and noticed the idle is different from usual when temp is reading 90+ degrees. The symptoms are that when coming to a standstill at a junction/lights etc and depressing the clutch the revs rise to about 1400rpm then after 5 secs fall to regular idle.
Guessing this is most likely to be the stepper motor but according to the service schedule it was cleaned about a fortnight ago when I took it to Fernhurst. Assuming it was actually cleaned.
Called Fernhurst but all the technicians had gone home.
I've looked at the guide which Davetherave sent me and it looks relatively simple to remove/clean although the photos are so small it isn't totally crystal also not helped by me being mechanically inept and with very limited tools.
Does anyone fancy giving me a hand tomorrow, Saturday 13th, to take it out and give it a clean. Alternatively I'll call Leven and see whether they're open and get a diagnosis of the problem, although I'm guessing they won't be around on a Saturday.
Any help welcomed in exchange for beer tokens!
Edited by Alex L on Friday 12th June 19:26
It's really easy, you'll be fine doing it by yourself IMHO. Remove wiring connector, unscrew stepper (you'll need a pair of grips to do this normally). Clean up (bit of petrol on a rag would be my approach, or some brake cleaner. Screw back in GENTLY, NOT TOO TIGHT or you'll risk cracking the plenum. Reconnect wiring.
Or, get the car idling nicely, then just unplug the stepper. I ran mine for months without the stepper connected and never had a single idle problem.
Or, get the car idling nicely, then just unplug the stepper. I ran mine for months without the stepper connected and never had a single idle problem.
Managed to undo it by hand, gave it a clean with white spirit and stuck it back in, haven't driven it yet as I need to shuffle some other cars around to get it out of the garage, hopefully all back to normal.
Does this look like it was cleaned a couple of weeks ago when the car was serviced?
This is the after shot
Does this look like it was cleaned a couple of weeks ago when the car was serviced?
This is the after shot
Edited by Alex L on Saturday 13th June 12:10
rigga said:
If you could undo it by hand that might be your problem..... not sealing properly and letting air past thus affecting the idle speed.....
It would have to be very loose to let enough air to affect the idle IMO. I had to clean mine (took mine out by hand) I tried it on just 1 thread and it didn't draw air.
However its probably not part of the service unless you asked for it to be cleaned. I used PTFE tape and with very little torque on the spanner managed to sheer the threaded part of the stepper from the rest of the body, so I wouldnt use it unless the sealing washer is completely US. I now tighten mine by hand then apply a miniscule of spanner torque afterwards.
This irratic idle problem is one of most common problems on the Chimaera there are a number of things that can cause it. The stepper is certainly a good place to start.
Mike
This irratic idle problem is one of most common problems on the Chimaera there are a number of things that can cause it. The stepper is certainly a good place to start.
Mike
Could do a full job (thanks to Mark @ blitzracing.co.uk) - worked fine for me (and that was single handed) ...
I have now perfected a way of getting them to bits to clean, without damage:
1) Get the car warm
2) Remove the stepper from the plenum and reconnect it. Block the hole where the stepper was with some sort of bung or strong tape to prevent air ingress.
3) Hold the stepper in your hand, so you can catch the central cone and spring when it comes out.
4) Get someone to start the car. Without the stepper in place it will rev at around 2k- 2.5k (This is noisey!!), but the ECU will try to slow it down by powering the stepper motor and pushing cone outwards. It will do this in a series of pulses, a few seconds apart, until the cone and spring drop out. (assuming they are not completely stuck). It may take a bit of manual help to get the cone to fully release. Now stop the engine and let it cool.
6) Clean all the muck of the shaft, and lightly lubricate the screw thread inside the motor.
7) To reassemble, wind the shaft back into the motor so far, but align the slot in the shaft with the plastic keyway as best you can by rotating the shaft in its screw thread
8)With the engine cool, then reconnect the stepper motor. Power cycle the ignition on and off, (don't start) and the ECU will try to pull the shaft back in each time the ignition is turned OFF. This is the slightly tricky bit, as if the keyway and shaft are not quite aligned it wont pull home, so you may need a few attempts.
I have now perfected a way of getting them to bits to clean, without damage:
1) Get the car warm
2) Remove the stepper from the plenum and reconnect it. Block the hole where the stepper was with some sort of bung or strong tape to prevent air ingress.
3) Hold the stepper in your hand, so you can catch the central cone and spring when it comes out.
4) Get someone to start the car. Without the stepper in place it will rev at around 2k- 2.5k (This is noisey!!), but the ECU will try to slow it down by powering the stepper motor and pushing cone outwards. It will do this in a series of pulses, a few seconds apart, until the cone and spring drop out. (assuming they are not completely stuck). It may take a bit of manual help to get the cone to fully release. Now stop the engine and let it cool.
6) Clean all the muck of the shaft, and lightly lubricate the screw thread inside the motor.
7) To reassemble, wind the shaft back into the motor so far, but align the slot in the shaft with the plastic keyway as best you can by rotating the shaft in its screw thread
8)With the engine cool, then reconnect the stepper motor. Power cycle the ignition on and off, (don't start) and the ECU will try to pull the shaft back in each time the ignition is turned OFF. This is the slightly tricky bit, as if the keyway and shaft are not quite aligned it wont pull home, so you may need a few attempts.
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