Dismantling the Stepper Motor
Discussion
When cleaning the stepper motor, I cant move the plunger in or out, it’s presently extended showing about 6mm of spring. I’ve bathed it in WD40, waggled and pulled it, just wont budge.
When wired up and with the ignition cycled, it still doesn’t move, but the motor buzz’s for a few seconds on switch off, which I think is normal.
I’ve read somewhere that it can be dismantled and have tried pushing in the three pins on the hex flat’s, but they wont go in far enough to release the connector. Do they just need a bit more persuasion ? or should leave this and try more push and pull with WD40.
Cheers,
Simon.
When wired up and with the ignition cycled, it still doesn’t move, but the motor buzz’s for a few seconds on switch off, which I think is normal.
I’ve read somewhere that it can be dismantled and have tried pushing in the three pins on the hex flat’s, but they wont go in far enough to release the connector. Do they just need a bit more persuasion ? or should leave this and try more push and pull with WD40.
Cheers,
Simon.
Just done mine and I pulled it out with some pliers, it comes out very very slowly, I thought mine wasnt going to come out. To put it back in you push it in as far as it will go and then, without screwing the whole unit back in, turn the ignition on and off about 3 or 4 times till it goes back in.
Hi,
There are two stages to cleaning the stepper,the first is what you have already done.T
The next step is to dismantle the inner rod,it will probably be very tight because it will be gummed up with carbon.
Place the cone on a piece of rubber or similsr and push until you release the inner plunger from the internal keyway.
Give the internal spring and arm a very good clean and reassemble,it is awkward to locate at first but once you've done it a couple of times then it get's easier.
cheers
John
There are two stages to cleaning the stepper,the first is what you have already done.T
The next step is to dismantle the inner rod,it will probably be very tight because it will be gummed up with carbon.
Place the cone on a piece of rubber or similsr and push until you release the inner plunger from the internal keyway.
Give the internal spring and arm a very good clean and reassemble,it is awkward to locate at first but once you've done it a couple of times then it get's easier.
cheers
John
blitzracing said:
10p !!!!! When i have some time i will be reading all that 
Wow thanks Mark that make’s very interesting reading.
My Griff runs but not properly, it all started with a dodgy Coil (major misfire, complete power loss) which has been replaced (intermotor cheap fixed the problem but wasn’t quite right), twice (second coil a Bosch much better power but still not right when hot), along with a new Ignition Amp (new Lucas item). I've checked the Lambda's (both the same but the range was from 1.12v to 0.02v could be my digital meter not settling quickly enough) and the Coolant Sensor is OK.
Starting, tick over and cold to warm running is fine (checked the stepper any way, which came apart fine after an overnight soak in WD40). Temp gauge is normal and when hot with the fans on override the temp comes down, but she still missing slightly and is a little down on power.
Not checked the fuel temp sensor, don’t suppose anybody knows the range.
I have now arranged for the loan of a fault code reader which I should get mid next week so we’ll see what the ECU says is wrong.
Cheers,
Simon.
My Griff runs but not properly, it all started with a dodgy Coil (major misfire, complete power loss) which has been replaced (intermotor cheap fixed the problem but wasn’t quite right), twice (second coil a Bosch much better power but still not right when hot), along with a new Ignition Amp (new Lucas item). I've checked the Lambda's (both the same but the range was from 1.12v to 0.02v could be my digital meter not settling quickly enough) and the Coolant Sensor is OK.
Starting, tick over and cold to warm running is fine (checked the stepper any way, which came apart fine after an overnight soak in WD40). Temp gauge is normal and when hot with the fans on override the temp comes down, but she still missing slightly and is a little down on power.
Not checked the fuel temp sensor, don’t suppose anybody knows the range.
I have now arranged for the loan of a fault code reader which I should get mid next week so we’ll see what the ECU says is wrong.
Cheers,
Simon.
Simon.b said:
I've checked the Lambda's (both the same but the range was from 1.12v to 0.02v could be my digital meter not settling quickly enough) and the Coolant Sensor is OK.
Starting, tick over and cold to warm running is fine (checked the stepper any way, which came apart fine after an overnight soak in WD40). Temp gauge is normal and when hot with the fans on override the temp comes down, but she still missing slightly and is a little down on power.
Not checked the fuel temp sensor, don’t suppose anybody knows the range.
I have now arranged for the loan of a fault code reader which I should get mid next week so we’ll see what the ECU says is wrong.
Cheers,
Simon.
The bit about the probe voltages are interesting. In an ideal world the ECU will hold the fueling close enough to the .2-.7 volt range. The problem occurs with a mis fire, there is a lot of residual oxygen in the exhaust gas, so the lambda probe picks this up as a lean mixture, so the ecu richens the mixture when its not needed so it can over richen the mixture to compensate. This can cause the voltage to swing above the 1.2 volts but having said that, just about every car Ive looked at does glitch above .7 volts, so it may just be inherent in the breed as they say. If you lambdas are switching as you say, I doubt you will get a fault code from the ECU, as it wont trip a fault code for minor glitches, and it takes quite a few seconds of a fault condition to register, so dont expect to much. If you are measuring the lambda probes, its worth extening your meter cables so it can be read in the cabin by a passenger, and try it under load. It should keep switching up to about 3400 rpm,(at less than 3/4 throttle) then hold at over .7 volts up to full rpm.Starting, tick over and cold to warm running is fine (checked the stepper any way, which came apart fine after an overnight soak in WD40). Temp gauge is normal and when hot with the fans on override the temp comes down, but she still missing slightly and is a little down on power.
Not checked the fuel temp sensor, don’t suppose anybody knows the range.
I have now arranged for the loan of a fault code reader which I should get mid next week so we’ll see what the ECU says is wrong.
Cheers,
Simon.
Temp probe.
40'c 1.1k-1.3k
60' 500-700 ohms
80' 300-400 ohms
Mark
Checked the fuel temp sensor and that was OK.
The lambda, under load, whilst driving did lock out at 3400, but it was reading between .8 and .9 volts with various runs in 3rd and 4th gear. When back in the garage I did a short stationary burst at 4000 rpm and then it locked out at .65 volts.
As before up until she got warm all was well, though I think she felt a bit snatchy on the throttle, not as smooth a drive as before the problems started, though this may just be me getting paranoid.
Cheers,
Simon.
The lambda, under load, whilst driving did lock out at 3400, but it was reading between .8 and .9 volts with various runs in 3rd and 4th gear. When back in the garage I did a short stationary burst at 4000 rpm and then it locked out at .65 volts.
As before up until she got warm all was well, though I think she felt a bit snatchy on the throttle, not as smooth a drive as before the problems started, though this may just be me getting paranoid.
Cheers,
Simon.
Errm ok so just exactly what does one do?
In the bible it just says remove it and clean it - nothing more.
Simon says grab your cone with pliers and pull hard
John says push your cone onto rubber to release the rod from the keyway.
One says push it back in presumably with pliers again and another says operate the ignition several times to draw it back in.
I just know I'd make a hash of this so now can some one please tell me in detail what is the correct way to remove the rod/cone/spring AND reassemble it? Then I'll have a go at it.
Thanks
In the bible it just says remove it and clean it - nothing more.
Simon says grab your cone with pliers and pull hard
John says push your cone onto rubber to release the rod from the keyway.
One says push it back in presumably with pliers again and another says operate the ignition several times to draw it back in.
I just know I'd make a hash of this so now can some one please tell me in detail what is the correct way to remove the rod/cone/spring AND reassemble it? Then I'll have a go at it.
Thanks
davidindevon said:
Errm ok so just exactly what does one do?
In the bible it just says remove it and clean it - nothing more.
Simon says grab your cone with pliers and pull hard
John says push your cone onto rubber to release the rod from the keyway.
One says push it back in presumably with pliers again and another says operate the ignition several times to draw it back in.
I just know I'd make a hash of this so now can some one please tell me in detail what is the correct way to remove the rod/cone/spring AND reassemble it? Then I'll have a go at it.
Thanks
Basically its a faily simple mechanism, simply a motor with a course screw thread that the plunger moves back and forth on. If you pull it with plyers or a vice, the thread needs to be free enough to allow the motor to spin, by the action of pulling the plunger on the thread, which is not always possible. It is possible to fool the ecu into winding the cone further out, by loosening the stepper thread right off and then starting the engine, which will now over rev, so the ecu now has to compensate for the extra distance by winding the cone further out. This may be enough to expose enough of the plunger rod out side its normal range of travel to allow you to clean the keyway where its sticking. When you put it back in, you need to align the plunger with a keyway. You can twist it back in so far before you reach the keyway, get it aligned, and then let the ignition cycle pull it back to its home position. You just need to be a bit careful but there is simply no "official way" to service the motor.In the bible it just says remove it and clean it - nothing more.
Simon says grab your cone with pliers and pull hard
John says push your cone onto rubber to release the rod from the keyway.
One says push it back in presumably with pliers again and another says operate the ignition several times to draw it back in.
I just know I'd make a hash of this so now can some one please tell me in detail what is the correct way to remove the rod/cone/spring AND reassemble it? Then I'll have a go at it.
Thanks
Mark
Oh Hello Mark,
Thanks for that.
I've had the stepper off the back of the plenum and can see the rod and spring clearly but I can't see down to it's connection with the motor.
I understand what you are saying - allowing some air leakage to push the cone forward slightly. However, it won't pull out any further. There must be an order of assembling the stepper and I thought reversing this would be easy (ish)
Do you know if the earlier post about pushing the cone onto a rubber pad will completely release the rod so that I can clean it along the whole of it's length? (which is what I would like to do as it clearly hasn't been done for a long time) I can't see how pushing cone onto something would release it though after reading your reply.
David
Thanks for that.
I've had the stepper off the back of the plenum and can see the rod and spring clearly but I can't see down to it's connection with the motor.
I understand what you are saying - allowing some air leakage to push the cone forward slightly. However, it won't pull out any further. There must be an order of assembling the stepper and I thought reversing this would be easy (ish)
Do you know if the earlier post about pushing the cone onto a rubber pad will completely release the rod so that I can clean it along the whole of it's length? (which is what I would like to do as it clearly hasn't been done for a long time) I can't see how pushing cone onto something would release it though after reading your reply.
David
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