Stepper motor stuck-in. What now?
Discussion
Hi all. I've had a problem for some time that the car starts and sometimes revs to 2K when stone cold and this continues until it's warm (5-10 mins drive).
I have cleaned the stepper motor but was not really dirty. Re-applied the PTFE tape and screwed back in by hand + nipped up tight.
Now though it is happening all the time. So I did what a lot of you have said and took a pair of mole grips and a rag and clamped off the air tube between the Plenum and the stepper motor.
Then removed the stepper motor, reconnected the electrical plug and put a rag in that hole as well.
Started the car and it ran at 500-600rpm I guess, but would just hold tick over.
So I then checked the position of the stepper motor and this had not moved at all. I'm assuming that it should come out a bit?
When I turn the car off I get the "burrrrrrr" as the stepper motor is retracting the pin. (but its already in)
So is the stepper fecked or what?
Can I get the stepper motor pin out?
Any advice welcome.
Simon
I have cleaned the stepper motor but was not really dirty. Re-applied the PTFE tape and screwed back in by hand + nipped up tight.
Now though it is happening all the time. So I did what a lot of you have said and took a pair of mole grips and a rag and clamped off the air tube between the Plenum and the stepper motor.
Then removed the stepper motor, reconnected the electrical plug and put a rag in that hole as well.
Started the car and it ran at 500-600rpm I guess, but would just hold tick over.
So I then checked the position of the stepper motor and this had not moved at all. I'm assuming that it should come out a bit?
When I turn the car off I get the "burrrrrrr" as the stepper motor is retracting the pin. (but its already in)
So is the stepper fecked or what?
Can I get the stepper motor pin out?
Any advice welcome.
Simon
Hi,
that sounds right to me, with clamped off bypass hose and blocked stepper hole the stepper motor will try and retract the spindle to allow more air in to the plenum to raise the idle. As its already fully retracted it can't move any further. If you unclamp the bypass hose and try again the stepper motor should extend the spindle to try and lower the idle speed. (Note, if your rag is stuffed too far in the stepper hole this may act like clamping the bypass hose and stop air entering the plenum from the bypass hose). If it works it will screw out the stepper spindle all the way, hold it to stop it flying apart when you try.
Ozstyle
that sounds right to me, with clamped off bypass hose and blocked stepper hole the stepper motor will try and retract the spindle to allow more air in to the plenum to raise the idle. As its already fully retracted it can't move any further. If you unclamp the bypass hose and try again the stepper motor should extend the spindle to try and lower the idle speed. (Note, if your rag is stuffed too far in the stepper hole this may act like clamping the bypass hose and stop air entering the plenum from the bypass hose). If it works it will screw out the stepper spindle all the way, hold it to stop it flying apart when you try.
Ozstyle
When the engine is hot, it should start with the stepper motor removed and all other connections the same. It will rev up past 3k rpm (mine did anyway). If you have the stepper motor connected to the loom when removed, the ECU will send a signal to drive the plunger out, attempting to reduce the air flow, and hence reduce the idle speed. Careful when you do this because the plunger will drive all the way out and off the end of the drive. It can be tricky to refit.
Many people do this deliberately in order to clean the stepper motor completely. I did it to check my system was working but turned off after only a couple of seconds to stop the plunger driving all the way off.
Many people do this deliberately in order to clean the stepper motor completely. I did it to check my system was working but turned off after only a couple of seconds to stop the plunger driving all the way off.
If you are, as it would seem, the hands on type then you need to get RoverGauge if you don't have it already.
Using RG you can wind the stepper in and out on command so you can both test it and also keep driving it until the plunger comes out at which point you can give it a really good clean. When clean you can pulse it (from RG) to get the plunger started on the thread and back into the stepper body.
Steve
Using RG you can wind the stepper in and out on command so you can both test it and also keep driving it until the plunger comes out at which point you can give it a really good clean. When clean you can pulse it (from RG) to get the plunger started on the thread and back into the stepper body.
Steve
Steve_D said:
If you are, as it would seem, the hands on type then you need to get RoverGauge if you don't have it already.
Using RG you can wind the stepper in and out on command so you can both test it and also keep driving it until the plunger comes out at which point you can give it a really good clean. When clean you can pulse it (from RG) to get the plunger started on the thread and back into the stepper body.
Steve
Yep Steve. I have got the RG. I will try it when I get the next chance.Using RG you can wind the stepper in and out on command so you can both test it and also keep driving it until the plunger comes out at which point you can give it a really good clean. When clean you can pulse it (from RG) to get the plunger started on the thread and back into the stepper body.
Steve
Thanks.
So to close this post:
I unscrewed the stepper motor and took it out, blocked the hole and clamped the bypass pipe.
Started the car (cold) just to let the oil circulate for a few seconds it runs then at 700-900 rpm.
Released the clamp and the rpm's went up (+/- 1500-1900), the stepper motor did not move!
So I gently pulled + twisted the pin with my hands for a good 10-20 seconds.
Then all of a sudden the pin moved out!!
I waited a bit longer and every 3-5 s the plunger would move further out (trying to regulate the air into the engine to bring the rpm's down).
So the pin came out and it was very dirty.(see photos below) I cleaned it up added a bit of copper grease and carefully put it back in.
Turned the ignition back on/off and the stepper motor tried to pull the pin back in.
I had a couple of attempts to align the pin in the hole correctly while turning the ignition on/off and then it slid back in.
N.B. The stepper motor only makes the wurrrrrr noise when the pin is fully home.
Simon
Dirty Stepper motor pin
Cleaned up and greased
I unscrewed the stepper motor and took it out, blocked the hole and clamped the bypass pipe.
Started the car (cold) just to let the oil circulate for a few seconds it runs then at 700-900 rpm.
Released the clamp and the rpm's went up (+/- 1500-1900), the stepper motor did not move!
So I gently pulled + twisted the pin with my hands for a good 10-20 seconds.
Then all of a sudden the pin moved out!!
I waited a bit longer and every 3-5 s the plunger would move further out (trying to regulate the air into the engine to bring the rpm's down).
So the pin came out and it was very dirty.(see photos below) I cleaned it up added a bit of copper grease and carefully put it back in.
Turned the ignition back on/off and the stepper motor tried to pull the pin back in.
I had a couple of attempts to align the pin in the hole correctly while turning the ignition on/off and then it slid back in.
N.B. The stepper motor only makes the wurrrrrr noise when the pin is fully home.
Simon
Dirty Stepper motor pin
Cleaned up and greased
Looks hopefull- you can use Rovergauge to move the stepper to check its working- typically adding or removing 30 steps is enough to cause a significant shift in idle. It does confuse the ECU somewhat when you do this as its not in control of the stepper, so it might cause the engine to die. Quite normal.
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