Stepper motor.... idle position
Discussion
Anyone know what might be amiss if the stepper is not returning promptly to 'idle'?... After some electrical gremlins associated with main fuse failure, I'm stuck with a 2k idle at junctions for maybe 10-15 secs while the thing sorts itself out. I'm assuming this might be to do with the ECU seeing a voltae drop and perhaps 'resetting' (not done a disconnect yet as that usually screws up running for a while on mine).
Another notch closer to an Emerald/Omex/Megasquirt or whatever
Another notch closer to an Emerald/Omex/Megasquirt or whatever
Stepper-motor that's the name I couldn't think of at yesterday's lunch
As usual I can only offer my experience
When I had my Griff (for three and a half years) and my mates had their Chims stepper-motor problems were not unknown altho' the cause was (my problems were worst of course, as always)
Intermitent problems with mine were at idle and sticking at about 1,500-2,000rpm no fun with a Rover V8 when slowing for bends/corners/stops/giveways
I paid for the stepper-motor to be looked at/cleaned that worked ok for a while, I then paid for a new stepper-motor to be fitted, I was told this would be a waste of time and money and it was
I never did solve the problem before I sold the car (I did advise the new owner, I tell everybody about all faults on my cars as you may have already seen on PH forums)
Hope you get yours sorted
Edited for spelling
As usual I can only offer my experience
When I had my Griff (for three and a half years) and my mates had their Chims stepper-motor problems were not unknown altho' the cause was (my problems were worst of course, as always)
Intermitent problems with mine were at idle and sticking at about 1,500-2,000rpm no fun with a Rover V8 when slowing for bends/corners/stops/giveways
I paid for the stepper-motor to be looked at/cleaned that worked ok for a while, I then paid for a new stepper-motor to be fitted, I was told this would be a waste of time and money and it was
I never did solve the problem before I sold the car (I did advise the new owner, I tell everybody about all faults on my cars as you may have already seen on PH forums)
Hope you get yours sorted
Edited for spelling
Edited by Sporting Bear on Monday 26th February 14:04
Noe sure what year your car is, but on mine (98) there is small box which is in the speedo circuit behind the dash. A little plastic thing about 3 inches by two by one.
When I had speedo problems I took this little box apart to find out what it did and if it was faulty.
It had a circuit for dividing down the pulses from the speed sensor which then went to the ECU. Do you have one of these on your car?
If you look in the bible it gives the pin out at the ECU for the speed sensor input, it might be worth checking you have a pulse train at the ECU with the car on jacks and in gear with the engine running.
I did have similar symptoms on my car when the speedo stopped working. Turned out to be the sensor and when replaced everything returned to normal.
I never did do a full investigation of the little black box however but I looked on t'internet for the IC fitted and it was a dividing IC. (I can't find the number now)
Hope its of some help.
Cheers
Paul
When I had speedo problems I took this little box apart to find out what it did and if it was faulty.
It had a circuit for dividing down the pulses from the speed sensor which then went to the ECU. Do you have one of these on your car?
If you look in the bible it gives the pin out at the ECU for the speed sensor input, it might be worth checking you have a pulse train at the ECU with the car on jacks and in gear with the engine running.
I did have similar symptoms on my car when the speedo stopped working. Turned out to be the sensor and when replaced everything returned to normal.
I never did do a full investigation of the little black box however but I looked on t'internet for the IC fitted and it was a dividing IC. (I can't find the number now)
Hope its of some help.
Cheers
Paul
GreenV8S said:
If you get the idle about right and then disconnect the stepper motor, does it eliminate the problem? That would confirm that it is caused by the stepper motor rather than e.g. leaky brake servo etc. It might also give you a hint for one possible way to address the problem.
Well, I did exactly what you're hinting at Pete, tonight. Thr bloody thing was sitting mostly at 2+k when just moving and until stopped for ages... so once it had settled to normal idle and with the motor still running I disconnected it and yep normal service resumed (as far as I can tell). Which leads me to ask, what the heck is the thing supposed to do anyway? My experience, in 5 + years of ownership, has been that it's just a pain... so what did the designer have in mind as its function, I assume there must have been one (anti-down change lock-up, blip on start-up etc)?
Anyone know what colour wires do what on it... seriously thinking about sticking a switch in circuit on an appropriate one to disable the thing? I assume just removing and blanking off will involve all sorts of other shenannigans to get the idle right?
pupp said:
what the heck is the thing supposed to do anyway? My experience, in 5 + years of ownership, has been that it's just a pain
Well I'm not telling you to take it off, but for what it's worth this is one of those things that I think is more trouble than it's worth - along with the slow return valve to the dizzy, and the hundred Amp random breakdown device. Disconnecting the plug is fine for a few hours or days to show you what it's like to drive. You will find that the idle speed goes up when the engine is hot and down when it's cold, and you might need to help it with the throttle for the first few minutes on cold days. I've never found that any great problem though.
If you plan to do away with it permanently I think you have two options. One is to remove the stepper motor and put a fixed adjuster in the hole to give you a constant air bypass flow. This can be a bit of a fiddle since the hole is rather big which makes it a big awkward to make up an adapter of your own. The other is to block off the bypass flow completely and wind the base idle up to give you the idle speed you want. You can do this either by putting a clamp on the hose (you can buy hose clamps for the job, intended for temporary use but they work fine long term too) or by shoving something inside one end of the hose - a blanking cap designed for ordinary 1/2" domestic copper pipe does the job nicely. Getting it out again would be a right fiddle so make sure you're sure before you do this. Alternatively remove the hose completely and just blank off the spigots on both ends, again you can get caps specifically designed for the job or make your own from a short bit of hose and a plug, another use for those plumbing bits.
GreenV8S said:
pupp said:
what the heck is the thing supposed to do anyway? My experience, in 5 + years of ownership, has been that it's just a pain
Well I'm not telling you to take it off, but for what it's worth this is one of those things that I think is more trouble than it's worth - along with the slow return valve to the dizzy, and the hundred Amp random breakdown device. Disconnecting the plug is fine for a few hours or days to show you what it's like to drive. You will find that the idle speed goes up when the engine is hot and down when it's cold, and you might need to help it with the throttle for the first few minutes on cold days. I've never found that any great problem though.
If you plan to do away with it permanently I think you have two options. One is to remove the stepper motor and put a fixed adjuster in the hole to give you a constant air bypass flow. This can be a bit of a fiddle since the hole is rather big which makes it a big awkward to make up an adapter of your own. The other is to block off the bypass flow completely and wind the base idle up to give you the idle speed you want. You can do this either by putting a clamp on the hose (you can buy hose clamps for the job, intended for temporary use but they work fine long term too) or by shoving something inside one end of the hose - a blanking cap designed for ordinary 1/2" domestic copper pipe does the job nicely. Getting it out again would be a right fiddle so make sure you're sure before you do this. Alternatively remove the hose completely and just blank off the spigots on both ends, again you can get caps specifically designed for the job or make your own from a short bit of hose and a plug, another use for those plumbing bits.
Right, having done without the thing for a bit, it's certainly 'better' without it whn up to temperature... really nice to have rock solid idle and the revs dropping straight to idle when off throttle. BUT it's pretty 'orrible on start up, when the stepper cleasrly does add benefit...
So..... I'm thinking I want to be able to switch it in and out of circuit. Anyone know how the feeds to the motor work? I think it's some sort of signal that's supplied rather than just a DC feed (anyone confirm?). Is it just as simple as installing a switch (maybe in the 'ground' assuming there's a 'positive' and a 'negative' signal for different travel directions on the motor. Plan is 'on' for cold start, then 'off' for normal running (or when it starts titting about). Or should I just skip the thing and ride the throttle for the first few mins (not great in the work multi storey)?
pupp said:
Anyone know how the feeds to the motor work? I think it's some sort of signal that's supplied rather than just a DC feed (anyone confirm?). Is it just as simple as installing a switch (maybe in the 'ground' assuming there's a 'positive' and a 'negative' signal for different travel directions on the motor. Plan is 'on' for cold start, then 'off' for normal running (or when it starts titting about).
None of you lot know then? Sheesh...
I know but if I tell you I'll have to kill you....
It is a four phase signal similar to that used on stepper motors where the combinations of the active signals on the wires will move the stepper motor round. To get the stepper motor to rotate, the phases are applied in a specific sequence so that the rotation is made up as a series on individual steps - hence stepper motor. Typically this sequence is provided by the ECU sending out the sequences.
No it is not a simple on-off switch.
It is a four phase signal similar to that used on stepper motors where the combinations of the active signals on the wires will move the stepper motor round. To get the stepper motor to rotate, the phases are applied in a specific sequence so that the rotation is made up as a series on individual steps - hence stepper motor. Typically this sequence is provided by the ECU sending out the sequences.
No it is not a simple on-off switch.
By far the biggest problems associated with poor idle stability is incorrectly set throtle pot.
Most people make the mistake of setting this with the engine off .. but as soon as you add inlet vacuum on the throttle plate then any spindle play moves the throttle pot away from the correct setting. unless you have the correct seting at idle you won't get correct operation of the stepper.
There seems to be a bit of differences in actual voltage settings on the throttle pot, but if you aim for a figure of 0.310-0.325volts at idle with engine running you'll be fine. Check this before doing anythin else .. if it turns out to be in spec then you'll have to think a bit laterally to get the idle you desire, but if it's out of spec then sort it and see what happens.
I even had a car in the other day which had got lots of nice induction stuff on it and an aftermarket throttle pot which was wired the wrong way around! the owner had put up with a poor idle for years because he thought that was how it was supposed to be. once corrected he had a properly working stepper for the first time!
Most people make the mistake of setting this with the engine off .. but as soon as you add inlet vacuum on the throttle plate then any spindle play moves the throttle pot away from the correct setting. unless you have the correct seting at idle you won't get correct operation of the stepper.
There seems to be a bit of differences in actual voltage settings on the throttle pot, but if you aim for a figure of 0.310-0.325volts at idle with engine running you'll be fine. Check this before doing anythin else .. if it turns out to be in spec then you'll have to think a bit laterally to get the idle you desire, but if it's out of spec then sort it and see what happens.
I even had a car in the other day which had got lots of nice induction stuff on it and an aftermarket throttle pot which was wired the wrong way around! the owner had put up with a poor idle for years because he thought that was how it was supposed to be. once corrected he had a properly working stepper for the first time!
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