Hi All,I recently had the stepper motor replaced on my 1996 2Ltr petrol 406, and would like to know how it operates please. I know it has a plunger which I think protudes down in to the air flow,but am unsure as to what actually makes it go in and out. Is it the increase and de-increase of air passing over it, or is it moved up and down by an electrical signal. If I know for sure how it operates ,it would give me a better clue as to whether the fault lies in the SM itself or the signal from the ECU.
I am wondering if it is posssibe that the fault i have is down to a sticking SM or down to an intermittent software gliche /dry joint in the ECU,any ideas please.
The Master Tech at my Peugeot Dealer replaced the SM in order to cure a weird tickover problem i have, which causes the car to "jerk" as I lift off the throttle,and tickover at 1200 RPM if i engage neutral while the car is still rolling. Once the car comes to a standstill,the revs steady out at 950rpm. Other times the symptoms reverse and the car does not jerk at all, but when i engage neutral the engine tries to stall,and just catches itself before steadying at 950RPM. Then the car will run ABSOLUTELY PERFECT for several days at a time.
The Master Tech said that he suspected the SM of sticking intermittently,but I am still getting the same fault.So far he has changed the "MAP" sensor,"Oxygen" sensor,"Stepper Motor" and throttle cable,and reset the "Adaptives" several times.. The engine fault light comes on at all sorts of times several times a day,which records "Faulty Oxygen sensor"
How does the Stepper Motor work please.
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lakemaligne
- 1.8 16v
- Posts: 88
- Joined: Fri May 23, 2008 1:10 pm
- Location: Rugby, Warwickshire.
How does the Stepper Motor work please.
MK1 1996 2Ltr 16v Petrol LX, 167,000 miles,was aiming for 200,000.
Re: How does the Stepper Motor work please.
The stepper motor basically pushes the throttle open a little when instructed by the ECU in order to let air in so it can idle when your foot's not on the accelerator. If you're having idling issues with a new one, give the throttle body and butterfly a good clean inside with carb cleaner and a rag since the throttle failing to close properly at rest can interfere with airflow and cause the intake to behave other than how the ECU thinks it should.
Another part of this system, which you haven't mentioned is the throttle position sensor. It's quite possible yours has contaminants/corrosion inside. Only suggestion is to take it off and try to clean it using electrical contact cleaner, or source another one from a scrappy or the dealers. They're not cheap parts from the dealers though.
If the Peugeot diag tool says "Faulty oxygen sensor" then there's four possibilities I can think of in order of likelihood:
1) The sensor's faulty
2) The wiring to the sensor is faulty
3) The ECU thinks the engine is running very VERY badly (a faulty throttle pot can indirectly cause this!)
4) The ECU's faulty
The easiest way to determine which is to see the live data while the engine's running and the fault is triggered... but this will require use of the Peugeot diagnostic tool.
Another part of this system, which you haven't mentioned is the throttle position sensor. It's quite possible yours has contaminants/corrosion inside. Only suggestion is to take it off and try to clean it using electrical contact cleaner, or source another one from a scrappy or the dealers. They're not cheap parts from the dealers though.
If the Peugeot diag tool says "Faulty oxygen sensor" then there's four possibilities I can think of in order of likelihood:
1) The sensor's faulty
2) The wiring to the sensor is faulty
3) The ECU thinks the engine is running very VERY badly (a faulty throttle pot can indirectly cause this!)
4) The ECU's faulty
The easiest way to determine which is to see the live data while the engine's running and the fault is triggered... but this will require use of the Peugeot diagnostic tool.
<steve_earwig> I think this forum is more about keeping our cars going with minimal outlay than giving our cars more reason to go bang
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lakemaligne
- 1.8 16v
- Posts: 88
- Joined: Fri May 23, 2008 1:10 pm
- Location: Rugby, Warwickshire.
Re: How does the Stepper Motor work please.
Hello mjb,Thank you for replying to my thread and sorry this is a bit long.
When you say "throttle position sensor",do you mean "throttle Potentiometer",if so ,Sorry I forget to mention that I also had the Throttle Potentiometer renewed last summer,which made no difference .I cleaned the inside of the throttle and butterfly with carb cleaner last summer,but to be honest it was pretty clean and cleaning it made no difference either.It opens and closes fully and smoothly.There is a funny little orange ball just inside the throttle intake which resembles a capacitor,I am guessing its some kind of air flow sensor,am i right.
Regarding the "Oxygen sensor" ,this has been replaced by two seperate dealers,thinking the first one was faulty,but it made no difference.Its a long shot i know and i am grasping at straws here,but the oxygen sensor is plugged into the front end of the CAT,which is the original one which has covered 154,000 miles. Is it possible that the CAT is somehow upsetting the oxygen sensor in some way with contaminates.
My problem now and again manifests itself during the first stage of opening and closing the throttle,ie,if i pull off very gently,the car hesitates,like a flat spot until the throttle is pushed past the "bad bit". The car jerks as the power abruptly shuts off, just as the throttle is nearly closed.What is weird is why some times the engine revs at 1200-1600rpm if i engage neutral while the car is still rolling,and only calms down to 950 rpm as the car comes to a halt,or tries to stall. It cannot make its mind up what to do. Funnily enough ,this morning it must have been in a good mood and every thing was behaving perfect.!!!
I am a University Technician and work with electrical circuits at work,and can solder,etc, and I would like to take the ECU out the car and dismantle it to see if there are any dry joints or other obvious faults causing this intermttent series of faults. What would I have to do once its back in the car,ie,setting up etc. Would you advise me to have an authorised ECU repair place look at my car instead.
When you say "throttle position sensor",do you mean "throttle Potentiometer",if so ,Sorry I forget to mention that I also had the Throttle Potentiometer renewed last summer,which made no difference .I cleaned the inside of the throttle and butterfly with carb cleaner last summer,but to be honest it was pretty clean and cleaning it made no difference either.It opens and closes fully and smoothly.There is a funny little orange ball just inside the throttle intake which resembles a capacitor,I am guessing its some kind of air flow sensor,am i right.
Regarding the "Oxygen sensor" ,this has been replaced by two seperate dealers,thinking the first one was faulty,but it made no difference.Its a long shot i know and i am grasping at straws here,but the oxygen sensor is plugged into the front end of the CAT,which is the original one which has covered 154,000 miles. Is it possible that the CAT is somehow upsetting the oxygen sensor in some way with contaminates.
My problem now and again manifests itself during the first stage of opening and closing the throttle,ie,if i pull off very gently,the car hesitates,like a flat spot until the throttle is pushed past the "bad bit". The car jerks as the power abruptly shuts off, just as the throttle is nearly closed.What is weird is why some times the engine revs at 1200-1600rpm if i engage neutral while the car is still rolling,and only calms down to 950 rpm as the car comes to a halt,or tries to stall. It cannot make its mind up what to do. Funnily enough ,this morning it must have been in a good mood and every thing was behaving perfect.!!!
I am a University Technician and work with electrical circuits at work,and can solder,etc, and I would like to take the ECU out the car and dismantle it to see if there are any dry joints or other obvious faults causing this intermttent series of faults. What would I have to do once its back in the car,ie,setting up etc. Would you advise me to have an authorised ECU repair place look at my car instead.
MK1 1996 2Ltr 16v Petrol LX, 167,000 miles,was aiming for 200,000.
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Welly
- The moderator formally known as Welton
- Posts: 15033
- Joined: Tue Jan 10, 2006 12:52 pm
- Location: East Midlandfordshire
Re: How does the Stepper Motor work please.
Have you ever looked closely at the ECU's multi-pin plug itself? these can corrode and cause bad signals from the various sensors etc 
Cars in my care:
2021 Kia Spottage 1.6 Pez Turbo Dual Clutch Gearbox Trickery
2013 Renner Twingo - donkey work
2021 Kia Spottage 1.6 Pez Turbo Dual Clutch Gearbox Trickery
2013 Renner Twingo - donkey work
Re: How does the Stepper Motor work please.
I'd suggest checking out the following in order:
Coolant temperature sensor (located near the thermostat)
Ambient air temperature sensor (may be the orange ball you mentioned)
MAF/MAP sensor (dunno which yours has got)
It's also possible your cat has broken down internally and is restricting airflow at low revs. Remove the oxygen sensor to test this. It can cause issues at low revs but I can't see it causing high idle revs...
Coolant temperature sensor (located near the thermostat)
Ambient air temperature sensor (may be the orange ball you mentioned)
MAF/MAP sensor (dunno which yours has got)
It's also possible your cat has broken down internally and is restricting airflow at low revs. Remove the oxygen sensor to test this. It can cause issues at low revs but I can't see it causing high idle revs...
<steve_earwig> I think this forum is more about keeping our cars going with minimal outlay than giving our cars more reason to go bang
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lakemaligne
- 1.8 16v
- Posts: 88
- Joined: Fri May 23, 2008 1:10 pm
- Location: Rugby, Warwickshire.
Re: How does the Stepper Motor work please.
Hello Welly, do i need to disconnect the battery when i unplug the ECU cable.If so will this cause any problems when i recconnect the plug and battery.Will I have to reset throttle position memory or other things.
Hello mjb, my 406 has a MAP sensor which was renewed last year. How do i check out the coolant and air sensor.The waxstat was replaced last year and the temp gauge and the garage diag reads 82 degrees which is spot on,so dont think that is the problem.
What can i expect to happen when i disconnect the Oxygen sensor,and will doing so cause any damage to system.
The CAT does not rattle and passes the emissions test with flying colours.
Hello mjb, my 406 has a MAP sensor which was renewed last year. How do i check out the coolant and air sensor.The waxstat was replaced last year and the temp gauge and the garage diag reads 82 degrees which is spot on,so dont think that is the problem.
What can i expect to happen when i disconnect the Oxygen sensor,and will doing so cause any damage to system.
The CAT does not rattle and passes the emissions test with flying colours.
MK1 1996 2Ltr 16v Petrol LX, 167,000 miles,was aiming for 200,000.
Re: How does the Stepper Motor work please.
Hi
You poor thing you have been subjected to the bain of modern dealer techies - just plug the diagnostic in and hope for the best. Most have not a clue how to put the data together. The most important feature of diagnostics is the live data produced as MJB has told you. Some of the fault codes may not be directly related to the actual fault. Since you have had considerable hit and miss work done it is now more difficult to pin point. Since your car is not OBD2 you need to read the sensors with an oscilloscope or a dealer tool. There are,however, many things you can check with a digital multimeter. Before you go jumping around just check there may be a sleep mode on yours before you disconnect the battery. On later models there is a set procedure for this, not sure with yours. This won't stop you checking the Lamda, TPI and idle control stepper. If you do a google you will find the method of checking various types of Lamdas and be careful you identify the the correct one - later ones don't like resitance checks etc. One thing that has not been mentioned is the simple TDC hall effect sensor which does create the fault you mention. A good techy would have oscilloscoped this first. If for example something causes a misfire then that creates fault codes and one will be the Oxygen sensor (Lambda) since this measures the amount of oxygen left in the gasses after combustion. Leaving a misfire in place will ultimately lead to a dead CAT over a very short period - yet it may not be that sensor - it is just being overwhelmed and trying to react to one or more cylinder passing unburnt fuel in the exhaust when the real culprit is maybe a spark plug, timing sensor or coil.
If you just want to know how a stepper motor works then ok - it is a motor that has radial electromagnets that respond individually to a an electrical pulse, negative or positive, to determine which direction of rotation is required. The ECU sends these pulses when it reads other sensor inputs which suggest to it what amount of air is required when idling compared with the throttle position - simples.
Of course there may be other problems but don't go just changing stuff willy nilly.
Good Luck
You poor thing you have been subjected to the bain of modern dealer techies - just plug the diagnostic in and hope for the best. Most have not a clue how to put the data together. The most important feature of diagnostics is the live data produced as MJB has told you. Some of the fault codes may not be directly related to the actual fault. Since you have had considerable hit and miss work done it is now more difficult to pin point. Since your car is not OBD2 you need to read the sensors with an oscilloscope or a dealer tool. There are,however, many things you can check with a digital multimeter. Before you go jumping around just check there may be a sleep mode on yours before you disconnect the battery. On later models there is a set procedure for this, not sure with yours. This won't stop you checking the Lamda, TPI and idle control stepper. If you do a google you will find the method of checking various types of Lamdas and be careful you identify the the correct one - later ones don't like resitance checks etc. One thing that has not been mentioned is the simple TDC hall effect sensor which does create the fault you mention. A good techy would have oscilloscoped this first. If for example something causes a misfire then that creates fault codes and one will be the Oxygen sensor (Lambda) since this measures the amount of oxygen left in the gasses after combustion. Leaving a misfire in place will ultimately lead to a dead CAT over a very short period - yet it may not be that sensor - it is just being overwhelmed and trying to react to one or more cylinder passing unburnt fuel in the exhaust when the real culprit is maybe a spark plug, timing sensor or coil.
If you just want to know how a stepper motor works then ok - it is a motor that has radial electromagnets that respond individually to a an electrical pulse, negative or positive, to determine which direction of rotation is required. The ECU sends these pulses when it reads other sensor inputs which suggest to it what amount of air is required when idling compared with the throttle position - simples.
Of course there may be other problems but don't go just changing stuff willy nilly.
Good Luck
Re: How does the Stepper Motor work please.
lakemaligne wrote:Hi All,I recently had the stepper motor replaced on my 1996 2Ltr petrol 406, and would like to know how it operates please. I know it has a plunger which I think protudes down in to the air flow,but am unsure as to what actually makes it go in and out. Is it the increase and de-increase of air passing over it, or is it moved up and down by an electrical signal. If I know for sure how it operates ,it would give me a better clue as to whether the fault lies in the SM itself or the signal from the ECU.
I am wondering if it is posssibe that the fault i have is down to a sticking SM or down to an intermittent software gliche /dry joint in the ECU,any ideas please.
The Master Tech at my Peugeot Dealer replaced the SM in order to cure a weird tickover problem i have, which causes the car to "jerk" as I lift off the throttle,and tickover at 1200 RPM if i engage neutral while the car is still rolling. Once the car comes to a standstill,the revs steady out at 950rpm. Other times the symptoms reverse and the car does not jerk at all, but when i engage neutral the engine tries to stall,and just catches itself before steadying at 950RPM. Then the car will run ABSOLUTELY PERFECT for several days at a time.
The Master Tech said that he suspected the SM of sticking intermittently,but I am still getting the same fault.So far he has changed the "MAP" sensor,"Oxygen" sensor,"Stepper Motor" and throttle cable,and reset the "Adaptives" several times.. The engine fault light comes on at all sorts of times several times a day,which records "Faulty Oxygen sensor"
When you mention oxygen Faulty Oxygen Sensor, did you know that you could have 2 oxygen sensors? Most cars have more than one, eg, pre cat and post cat.
If your car was a Vauxhall, your symptons would lead me to a faulty EGR valve, it's a classic problem on those, however it aint a vauxhall
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lakemaligne
- 1.8 16v
- Posts: 88
- Joined: Fri May 23, 2008 1:10 pm
- Location: Rugby, Warwickshire.
Re: How does the Stepper Motor work please.
My car did something new this morning.It started fine ,then instead of ticking over at the usual 1100 -1200 rpm for the first couple of minutes until the engine settled down and started warming up,it started to rev up to 1500 rpm then down to 900 rpm ,then back up to 1200 rpm . It then cycled like this for quite a while ,then eased off to the normal rpm.Then once i had started driving the car it went into "nearly stalling " mode each time i stopped at a junction.
Little Lad,
Yes i agree i have been messed about by incompetent techies,naively believing that they would just plug in their magic box and sort it .Unfortunately I now suffer from very painful sciatica and cannot spend ages fault finding on cars like i used to in my youth.
When you refer to "sleep mode" are you refering to the residual voltage left in the system after the battery has been disconnected.I found an article on the web about "sleep mode" and telling me to press the horn push once the battery has been disconnected to completely discharge any voltage left in the system and wipe any previous memory settings.Would you advise me doing this,then afterwards re-teach the drive cycle again.
Little Lad,do you live any where near Rugby in the midlands by any chance,because if you do ,you sound like you know your way round 406's and fault finding and would'nt mind paying you to have a look at my 406. My car is worth spending money on someone who knows how to fault find properly as she has performed faultlessly and never broke down on me once since i bought her new in 1996,apart from this intermittent fault that is. (touch wood)
Little Lad,
Yes i agree i have been messed about by incompetent techies,naively believing that they would just plug in their magic box and sort it .Unfortunately I now suffer from very painful sciatica and cannot spend ages fault finding on cars like i used to in my youth.
When you refer to "sleep mode" are you refering to the residual voltage left in the system after the battery has been disconnected.I found an article on the web about "sleep mode" and telling me to press the horn push once the battery has been disconnected to completely discharge any voltage left in the system and wipe any previous memory settings.Would you advise me doing this,then afterwards re-teach the drive cycle again.
Little Lad,do you live any where near Rugby in the midlands by any chance,because if you do ,you sound like you know your way round 406's and fault finding and would'nt mind paying you to have a look at my 406. My car is worth spending money on someone who knows how to fault find properly as she has performed faultlessly and never broke down on me once since i bought her new in 1996,apart from this intermittent fault that is. (touch wood)
MK1 1996 2Ltr 16v Petrol LX, 167,000 miles,was aiming for 200,000.
Re: How does the Stepper Motor work please.
Hi
Sadly I'm in West yorkshire but my advise to you is first try and get hold of a second hand oscilloscope it will help you test all sensors easily and there are many samples of waveforms on the net - look at Pico ( I don't get commission) they are very good on this subject. I agree, peugeots are a great car spoilt by the rip off attitude of their dealers (Stealers). The PSA small diesels are arguably the best in the world and your petrol engine is as good. I'm from the old school of diagnostics and have grown with the changes in technology whilst retaining the values of traditional engineering. I have to say it has changed for the better but sadly has produced a mentality of plug and play and of monopoly. If you can afford it get hold of Lexia 3 or Generic scanner though the latter won't do anything for your current model. I have just had to reluctantly purchase a Lexia since it is getting an essential piece of kit because manufacturers are increasingly producing parts that require pairing. Just a cautionary note I cannot get mine to work at the moment (Chinese from Ebay) But they are trying to resolve the problem. Others have been quite successful so I may have a bad batch model. The main theme of this is to point out that if you had one and could connect it to your car I could look at the data file and better assess what your problem might be. Many people come onto forums and give misleading observations which is almost impossible to determine a fault - we can only give possibilities which is probably as bad as taking it to a stealer. We/I (not this forum)are working on a method of actually seeing live date via the internet just like the planet system does with their dealers. However, back to your motor. If you look up BBA Reman on the internet they have a procedure for putting the system to sleep on Peugeots. Basically you turn everything off (including anything in your cig lighter) open the window so you can get in to use the ignition etc (oh and lift your bonnet) then leave it alone for 3 mins so it goes to sleep. Then you can disconnect the battery. There is a procedure for also waking it back up again when you reconnect. The ECU will relearn things after any alteration automatically - for this to occur you must go for a run so that it can do this otherwise it may appear to be erratic just after any change - this has often thrown people into thinking they still have a fault. Because current systems use a BSI (Body systems Interface) to handle things other than engine controls on the VAN (vehicle Area Network) there is a constant communication between the ECU and the BSI and if you disturb this before it goes into rest you can disrupt the little chats they do and it can cause problems. The new systems are going on to CAN (Central Area Network) which offers more prioritising of controllers. Alas you do need to have some ability to understand how things work or all I have said will be double Dutch and I would simply hate to think you might end up chasing your tail. Incidentally - they have changed the way idle control stepper motors work so I'm not sure which yours is - they used to push on the Butterfly spindle but changed this to simply open a valve to allow air in to bypass the butterfly and this works very fast indeed and allows better monitoring of the TPI it can also cause a problem if it does stick open since it makes the mixture weak in the closed loop but should not affect it when accelerating hard since the system goes into open loop for this.
The symptom you just mentioned could well be attributed to the idlecontrol valve (if it is this type) there are three basic systems Bosch, Sagem and Mirreli, all basically the same. Again don't go jumping around before testing things and the wiring ,take a logical stance. You know, if all that stuff you just had changed was since new, you have done very well indeed.
Sadly I'm in West yorkshire but my advise to you is first try and get hold of a second hand oscilloscope it will help you test all sensors easily and there are many samples of waveforms on the net - look at Pico ( I don't get commission) they are very good on this subject. I agree, peugeots are a great car spoilt by the rip off attitude of their dealers (Stealers). The PSA small diesels are arguably the best in the world and your petrol engine is as good. I'm from the old school of diagnostics and have grown with the changes in technology whilst retaining the values of traditional engineering. I have to say it has changed for the better but sadly has produced a mentality of plug and play and of monopoly. If you can afford it get hold of Lexia 3 or Generic scanner though the latter won't do anything for your current model. I have just had to reluctantly purchase a Lexia since it is getting an essential piece of kit because manufacturers are increasingly producing parts that require pairing. Just a cautionary note I cannot get mine to work at the moment (Chinese from Ebay) But they are trying to resolve the problem. Others have been quite successful so I may have a bad batch model. The main theme of this is to point out that if you had one and could connect it to your car I could look at the data file and better assess what your problem might be. Many people come onto forums and give misleading observations which is almost impossible to determine a fault - we can only give possibilities which is probably as bad as taking it to a stealer. We/I (not this forum)are working on a method of actually seeing live date via the internet just like the planet system does with their dealers. However, back to your motor. If you look up BBA Reman on the internet they have a procedure for putting the system to sleep on Peugeots. Basically you turn everything off (including anything in your cig lighter) open the window so you can get in to use the ignition etc (oh and lift your bonnet) then leave it alone for 3 mins so it goes to sleep. Then you can disconnect the battery. There is a procedure for also waking it back up again when you reconnect. The ECU will relearn things after any alteration automatically - for this to occur you must go for a run so that it can do this otherwise it may appear to be erratic just after any change - this has often thrown people into thinking they still have a fault. Because current systems use a BSI (Body systems Interface) to handle things other than engine controls on the VAN (vehicle Area Network) there is a constant communication between the ECU and the BSI and if you disturb this before it goes into rest you can disrupt the little chats they do and it can cause problems. The new systems are going on to CAN (Central Area Network) which offers more prioritising of controllers. Alas you do need to have some ability to understand how things work or all I have said will be double Dutch and I would simply hate to think you might end up chasing your tail. Incidentally - they have changed the way idle control stepper motors work so I'm not sure which yours is - they used to push on the Butterfly spindle but changed this to simply open a valve to allow air in to bypass the butterfly and this works very fast indeed and allows better monitoring of the TPI it can also cause a problem if it does stick open since it makes the mixture weak in the closed loop but should not affect it when accelerating hard since the system goes into open loop for this.
The symptom you just mentioned could well be attributed to the idlecontrol valve (if it is this type) there are three basic systems Bosch, Sagem and Mirreli, all basically the same. Again don't go jumping around before testing things and the wiring ,take a logical stance. You know, if all that stuff you just had changed was since new, you have done very well indeed.
-
lakemaligne
- 1.8 16v
- Posts: 88
- Joined: Fri May 23, 2008 1:10 pm
- Location: Rugby, Warwickshire.
Re: How does the Stepper Motor work please.
Hello Little Lad,
That’s a shame , West Yorkshire is a bit far away for me to pop round. You sound like the sort of chap that could have sorted out my 406, with payment of course.
First of all , can I just add yet another symptom which I have just noticed which may help. While sitting at the traffic lights the other day ,hand brake on, engine ticking over at a smooth 950rpm, I let the car start to roll forward and noticed the revs start to rise steadily as the cars momentum increased.. The revs dropped down again the moment the car came to a halt. I may be wrong , but to me ,this seems like the ECU is getting its wires crossed and telling the SM to open up a wee bit when it shouldn’t. The symptoms manifest themselves after the car has been driven very slowly ,say in a traffic jam for a few minutes .
Regarding SM operation, mine is the later type which actuates an air by-pass valve. I think my system is Mirrelli.
I have pulled up the “Sleep procedure “ on the BBA Reman site you mentioned and printed it out.
The Lexia 3 scanner you mentioned looks a pricey piece of kit and is a bit out of my price range I am afraid for the amount of time I would use it. As I do not want to set my sciatica off, before I go crawling around under my car, I will first get a quote from a local ECU tester ,to see if they chuck up any faults on my ECU. If they are too pricey , I might get one from a scrap yard, making sure I get the code for the key pad which I believe is stored in the ECU. Would this present any problems do you know. If that fails, I will try to get hold of a scope and start looking at wave forms, etc.
The Master Tech who has been trying to fix my car,(he also owns a 406), has a very strong suspicion that the ECU is to blame, because I cannot see how the SM or other new sensors can be faulty one day ,then run fine for several days. Could my cars mileage (154,000) due to worn engine maybe, be causing excessive oil vapour to clog the SM now and then, just a thought.
Instead of relying on this forum to keep you up to date with my progress, would you mind if we used email.
That’s a shame , West Yorkshire is a bit far away for me to pop round. You sound like the sort of chap that could have sorted out my 406, with payment of course.
First of all , can I just add yet another symptom which I have just noticed which may help. While sitting at the traffic lights the other day ,hand brake on, engine ticking over at a smooth 950rpm, I let the car start to roll forward and noticed the revs start to rise steadily as the cars momentum increased.. The revs dropped down again the moment the car came to a halt. I may be wrong , but to me ,this seems like the ECU is getting its wires crossed and telling the SM to open up a wee bit when it shouldn’t. The symptoms manifest themselves after the car has been driven very slowly ,say in a traffic jam for a few minutes .
Regarding SM operation, mine is the later type which actuates an air by-pass valve. I think my system is Mirrelli.
I have pulled up the “Sleep procedure “ on the BBA Reman site you mentioned and printed it out.
The Lexia 3 scanner you mentioned looks a pricey piece of kit and is a bit out of my price range I am afraid for the amount of time I would use it. As I do not want to set my sciatica off, before I go crawling around under my car, I will first get a quote from a local ECU tester ,to see if they chuck up any faults on my ECU. If they are too pricey , I might get one from a scrap yard, making sure I get the code for the key pad which I believe is stored in the ECU. Would this present any problems do you know. If that fails, I will try to get hold of a scope and start looking at wave forms, etc.
The Master Tech who has been trying to fix my car,(he also owns a 406), has a very strong suspicion that the ECU is to blame, because I cannot see how the SM or other new sensors can be faulty one day ,then run fine for several days. Could my cars mileage (154,000) due to worn engine maybe, be causing excessive oil vapour to clog the SM now and then, just a thought.
Instead of relying on this forum to keep you up to date with my progress, would you mind if we used email.
MK1 1996 2Ltr 16v Petrol LX, 167,000 miles,was aiming for 200,000.
Re: How does the Stepper Motor work please.
Hi
Sorry for not responding earlier - I've been very busy. If you would like to send a PM to me that's oK by me - I would be very interested in the outcome. Intermitant faults are a nightmare and not helped by well meaning people offering tips of "what it could be". Possessing an oscilloscope is almost a required element with todays electronic gismos not just cars. Many technicians don't use them because they become complacent, once they get a particular fault on one make of car they assume it will be repeated - often they are right, however, there are so many combinations of faults that can exhibit the same symptom, it is crazy to just go changing stuff at £100 a plop. Injectors for example, offer a waveform that can illustrate the tiny intermittant fluctuations throughout the speed range and so without a scope how would you read that? Having said that manufactureres are not making it easier to use when they design systems that we cannot even get a probe on.
Good luck in your endeavers.
John
Sorry for not responding earlier - I've been very busy. If you would like to send a PM to me that's oK by me - I would be very interested in the outcome. Intermitant faults are a nightmare and not helped by well meaning people offering tips of "what it could be". Possessing an oscilloscope is almost a required element with todays electronic gismos not just cars. Many technicians don't use them because they become complacent, once they get a particular fault on one make of car they assume it will be repeated - often they are right, however, there are so many combinations of faults that can exhibit the same symptom, it is crazy to just go changing stuff at £100 a plop. Injectors for example, offer a waveform that can illustrate the tiny intermittant fluctuations throughout the speed range and so without a scope how would you read that? Having said that manufactureres are not making it easier to use when they design systems that we cannot even get a probe on.
Good luck in your endeavers.
John