Dave, sadly there’s no way I can answer the question you pose, but I did want to tell you I’m full of admiration for your incredible persistence chasing down a solution to this problem.
CB1100 Idle speed instability problem
- Thread starter ericlo69_imp
- Start date
max
Road warrior
Hi Dave, big learning curve by the sound of it, however you have made the journey into the forest, the way out should be easyer.
Q1; was the iacv disconnected when you removed it? picking it was connected.
q2; now that they are both out is there a difference in binding the threaded part i.o.w. does the old one run freely?
a1; position of the piston inside; it has worked fine before all the trouble started so unless the ecm has slowly dribbled out of position ( stuck during part of the travel and still counted the same amount of steps ) i expect it to be correct.
"There is something potentially wrong with the way the valve came out though. I expected the valve to have been positioned all the way to its "as-installed" location, which is the valve rotated clockwise the full length of its travel on the threaded shaft, (this is how the FSM instructs you to install the valve) but instead, it was about 1/3 of what I "estimate" to be its full travel in the opposite direction."
As far as i can work it out it chases a moving setpoint depending on air and engine temperatures so it should have a tendency to "shuffle"along the working part of the cylinder and resets to a pre- determined position every time the engine is started from cold.
In other words it automatically finds it's own spot.
The concern i had was if the piston was initially mounted too far into the barrel ( not wound back ) and the thread was compressed against the end of the barrel where it has a minimal amount of threads on initialisation.
I think the real answer is that you would need an obd2 tool to tell exactly where the piston is at any time, however we know that it is not in the target position if the engine idles badly, so you can reliably guess when it is too far open or closed.
( if you can see the shadow of a tree you know the tree is there otherwise what makes the shadow?)
a 2; if the iacv was connected and the bike idled ok prior to being switched off the iacv was indeed in the correct operating position for a warmed up engine, well done Dave.
Could it be that the valve was on an angle in the barrel? ( Minor scuff marks at the very end of the tip of the piston )
Can we have a look at pictures of both iacv's prior to mounting the new one?
Q1; was the iacv disconnected when you removed it? picking it was connected.
q2; now that they are both out is there a difference in binding the threaded part i.o.w. does the old one run freely?
a1; position of the piston inside; it has worked fine before all the trouble started so unless the ecm has slowly dribbled out of position ( stuck during part of the travel and still counted the same amount of steps ) i expect it to be correct.
"There is something potentially wrong with the way the valve came out though. I expected the valve to have been positioned all the way to its "as-installed" location, which is the valve rotated clockwise the full length of its travel on the threaded shaft, (this is how the FSM instructs you to install the valve) but instead, it was about 1/3 of what I "estimate" to be its full travel in the opposite direction."
As far as i can work it out it chases a moving setpoint depending on air and engine temperatures so it should have a tendency to "shuffle"along the working part of the cylinder and resets to a pre- determined position every time the engine is started from cold.
In other words it automatically finds it's own spot.
The concern i had was if the piston was initially mounted too far into the barrel ( not wound back ) and the thread was compressed against the end of the barrel where it has a minimal amount of threads on initialisation.
I think the real answer is that you would need an obd2 tool to tell exactly where the piston is at any time, however we know that it is not in the target position if the engine idles badly, so you can reliably guess when it is too far open or closed.
( if you can see the shadow of a tree you know the tree is there otherwise what makes the shadow?)
a 2; if the iacv was connected and the bike idled ok prior to being switched off the iacv was indeed in the correct operating position for a warmed up engine, well done Dave.
Could it be that the valve was on an angle in the barrel? ( Minor scuff marks at the very end of the tip of the piston )
Can we have a look at pictures of both iacv's prior to mounting the new one?
the Ferret
Road warrior
I can't imagine living anyplace where I would be in stop and go traffic for more than an hour. What a nightmare that must be.Dude_imp said:
Hi Cormanus, thank you very much. I have to thank all the great people on this forum who have encouraged and supported me the whole way. The job is only half way done now, and I am praying that the new IACV will cure this idle problem.Cormanus_imp said:
Q1; was the iacv disconnected when you removed it? picking it was connected.
It was disconnected for the last 50 miles I rode the bike, with slow idle on start-up, and perfect idle with the engine warmed up.
q2; now that they are both out is there a difference in binding the threaded part i.o.w. does the old one run freely?
No. Both valves thread very smoothly the full range of travel on the threaded shaft.
a1; position of the piston inside; it has worked fine before all the trouble started so unless the ecm has slowly dribbled out of position ( stuck during part of the travel and still counted the same amount of steps ) i expect it to be correct.
This is a possibility. I posted a while back that the sound I heard when I first turned the key on became noticeably louder on one occasion. It could have been the IACV noise, but then again it may have been the fuel pump.
As far as i can work it out it chases a moving setpoint depending on air and engine temperatures so it should have a tendency to "shuffle"along the working part of the cylinder and resets to a pre- determined position every time the engine is started from cold.
In other words it automatically finds it's own spot.
Question: If it finds its own spot, can it automatically compensate if it is installed incorrectly - ie, if the valve is not threaded completely to the bottom of the threads on installation?
The concern i had was if the piston was initially mounted too far into the barrel ( not wound back ) and the thread was compressed against the end of the barrel where it has a minimal amount of threads on initialisation.
I think the real answer is that you would need an obd2 tool to tell exactly where the piston is at any time, however we know that it is not in the target position if the engine idles badly, so you can reliably guess when it is too far open or closed.
( if you can see the shadow of a tree you know the tree is there otherwise what makes the shadow?)
a 2; if the iacv was connected and the bike idled ok prior to being switched off the iacv was indeed in the correct operating position for a warmed up engine, well done Dave.
The bike idled fine when warned-up, with the IACV disconnected (which it was for about the last 50 miles, and three around town trips). Do you think it's possible that the valve somehow moved (vibration?) during the 50 miles I traveled with it disconnected? I am guessing that it would not.
Could it be that the valve was on an angle in the barrel? ( Minor scuff marks at the very end of the tip of the piston )
I don't believe so. There is no visible indication of any kind f damage or scuff marks, and the valve removed effortlessly from the cylinder, indicating no binding at all.
Can we have a look at pictures of both iacv's prior to mounting the new one?
[/QUOTE]
I will provide pictures, but you won't see any difference between the two valves.
My next step will be to reinstall the battery and test both old and new IACVs side-by-side. I hope they will work - I have disconnected many wires that I don't know if this will have any effect. I did inspect the new IACV prior to any disassembly and it appeared to function properly (to the best of my knowledge, anyway). I can only compare the old to the new to see if there is a difference.
max
Road warrior
Nice going Dave, in order of appearance;
Disconnected in the running position and idling perfect for 50 miles, you stated it before but i like the sound of that!
a1; don't think it moved, which brings me to the first question; you know more about the iacv movement now, so can the shaft rotate when it is not electrically energized or is the shaft stuck or magnetically held in position ( moving but you can feel the magnetic poles hold the shaft ) when you try to rotate it?
My feeling is that the stepper motor was gradually having more difficulty in moving the shaft, reasons i can think of are;
piston not aligned with the barrel, thread binding ( i think you eliminated both of these ) pin that guides the piston too short or too long, bearings inside the stepper motor running low on lubrication, are the two stepper motors evenly strong or is one weaker? and lastly something inside the iacv motor that got in the way ( debris )
Is the piston made of plastic or metal?
can the piston unscrew completely from the shaft or is there a stop at the end and are the springs the same strength?
When you install the battery i think the iacv ( plugged in but not mounted so you can see what it is doing ) will cycle as normal, it will even do this in limp mode because it is part of the initialisation and the computer is not making a decision yet, it only sets the engine up for warm or cold start.
If you hold the piston with your fingers you can see it travel in or out ( forgot which way but it is not important for now ) .
The ecm does not know where the iacv piston is on startup, so the engineers have programmed a simple routine in the ecm by extending the travel a few steps more than required to get to one end ( either open or closed ) from there it knows the piston is at the end of travel and moves the piston in reverse----- by the amount of steps required for the operating temperature ect.----- and now the ecm knows that the piston is in the correct position to start the engine.
This always works ok on startup, every time, but something happens sometimes after some time that makes the ecm think the piston is in the right place but it dragged it's feet and is somewhere else.
I would listen to any noise that is different between old and new iacv, i am sure you have given us the clue with the different sound when it is not behaving but i cannot decode the hint for now.
If you switch on in the 30% ( warm running position in which you found it ) i think it will go to one end first and then move back some distance.
Thank you Dave.
Disconnected in the running position and idling perfect for 50 miles, you stated it before but i like the sound of that!
a1; don't think it moved, which brings me to the first question; you know more about the iacv movement now, so can the shaft rotate when it is not electrically energized or is the shaft stuck or magnetically held in position ( moving but you can feel the magnetic poles hold the shaft ) when you try to rotate it?
My feeling is that the stepper motor was gradually having more difficulty in moving the shaft, reasons i can think of are;
piston not aligned with the barrel, thread binding ( i think you eliminated both of these ) pin that guides the piston too short or too long, bearings inside the stepper motor running low on lubrication, are the two stepper motors evenly strong or is one weaker? and lastly something inside the iacv motor that got in the way ( debris )
Is the piston made of plastic or metal?
can the piston unscrew completely from the shaft or is there a stop at the end and are the springs the same strength?
When you install the battery i think the iacv ( plugged in but not mounted so you can see what it is doing ) will cycle as normal, it will even do this in limp mode because it is part of the initialisation and the computer is not making a decision yet, it only sets the engine up for warm or cold start.
If you hold the piston with your fingers you can see it travel in or out ( forgot which way but it is not important for now ) .
The ecm does not know where the iacv piston is on startup, so the engineers have programmed a simple routine in the ecm by extending the travel a few steps more than required to get to one end ( either open or closed ) from there it knows the piston is at the end of travel and moves the piston in reverse----- by the amount of steps required for the operating temperature ect.----- and now the ecm knows that the piston is in the correct position to start the engine.
This always works ok on startup, every time, but something happens sometimes after some time that makes the ecm think the piston is in the right place but it dragged it's feet and is somewhere else.
I would listen to any noise that is different between old and new iacv, i am sure you have given us the clue with the different sound when it is not behaving but i cannot decode the hint for now.
If you switch on in the 30% ( warm running position in which you found it ) i think it will go to one end first and then move back some distance.
Thank you Dave.
Is the piston made of plastic or metal?
It is not magnetic. I think it's aluminum (it's real light weight), but it is shiny in appearance. It's possible that it's a hard plastic, and I will have a closer look at this and get back with a better answer.
can the piston unscrew completely from the shaft or is there a stop at the end and are the springs the same strength?
The piston can be unthreaded from the shaft. What springs are you referring to?
The ecm does not know where the iacv piston is on startup, so the engineers have programmed a simple routine in the ecm by extending the travel a few steps more than required to get to one end ( either open or closed ) from there it knows the piston is at the end of travel and moves the piston in reverse----- by the amount of steps required for the operating temperature ect.----- and now the ecm knows that the piston is in the correct position to start the engine.
So does this mean that if the valve is not threaded down completely when it is installed (like mine was when I removed it) then the ECM will automatically compensate and send the proper signal to the motor to properly locate the valve?
I would listen to any noise that is different between old and new iacv, i am sure you have given us the clue with the different sound when it is not behaving but i cannot decode the hint for now.
I will operate both valves while holding them in my hand and report back my observations.
If you switch on in the 30% ( warm running position in which you found it ) i think it will go to one end first and then move back some distance.
So, then the fact that my valve was not threaded completely to the bottom of the threads when I removed it (the way it is supposed to be when installed) makes no difference? I was hoping that this was the root cause of my problem.
Thank you so much for your help Max. I don't think I'll be able to get back to the bike until this Saturday, but I will keep this thread updated as I progress.
It is not magnetic. I think it's aluminum (it's real light weight), but it is shiny in appearance. It's possible that it's a hard plastic, and I will have a closer look at this and get back with a better answer.
can the piston unscrew completely from the shaft or is there a stop at the end and are the springs the same strength?
The piston can be unthreaded from the shaft. What springs are you referring to?
The ecm does not know where the iacv piston is on startup, so the engineers have programmed a simple routine in the ecm by extending the travel a few steps more than required to get to one end ( either open or closed ) from there it knows the piston is at the end of travel and moves the piston in reverse----- by the amount of steps required for the operating temperature ect.----- and now the ecm knows that the piston is in the correct position to start the engine.
So does this mean that if the valve is not threaded down completely when it is installed (like mine was when I removed it) then the ECM will automatically compensate and send the proper signal to the motor to properly locate the valve?
I would listen to any noise that is different between old and new iacv, i am sure you have given us the clue with the different sound when it is not behaving but i cannot decode the hint for now.
I will operate both valves while holding them in my hand and report back my observations.
If you switch on in the 30% ( warm running position in which you found it ) i think it will go to one end first and then move back some distance.
So, then the fact that my valve was not threaded completely to the bottom of the threads when I removed it (the way it is supposed to be when installed) makes no difference? I was hoping that this was the root cause of my problem.
Thank you so much for your help Max. I don't think I'll be able to get back to the bike until this Saturday, but I will keep this thread updated as I progress.
Magnus_imp
First service completed
Dave,
If you run into any trouble I'm in San Diego as well and did the IACV a while ago as you probably know. I think I remember most of it. Sounds like you have a good hand on it and are taking it slow. But if you get truly stuck I'll be around this weekend. I could bring my CB so you can compare parts/wiring locations if you get lost. Eight Five Eight Nine 6 7 5 4 Eight 0
- John
If you run into any trouble I'm in San Diego as well and did the IACV a while ago as you probably know. I think I remember most of it. Sounds like you have a good hand on it and are taking it slow. But if you get truly stuck I'll be around this weekend. I could bring my CB so you can compare parts/wiring locations if you get lost. Eight Five Eight Nine 6 7 5 4 Eight 0
- John
I have to say, knowing of this just made my day--and I'm not even Dave.Magnus_imp said:
:beerchug:
Houtman_imp
Road warrior
I have to say, knowing of this just made my day--and I'm not even Dave.pdedse_imp said:I have to say, knowing of this just made my day--and I'm not even Dave.Magnus_imp said:
:beerchug:
:beerchug:
Plus One !!!
max
Road warrior
Thanks magnus, i hope Dave will take you up on that offer, you can't beat experience and Dave--- deserves--- all the assistance he can get, very few guys are as persistent as he is and i can't prase his efforts enough.
If the piston is made out of plastic it may be affected by heat somehow.
Here is the spring in front of the piston;
___So does this mean that if the valve is not threaded down completely when it is installed (like mine was when I removed it) then the ECM will automatically compensate and send the proper signal to the motor to properly locate the valve?
Depending on the forces involved it may be a reason for failure, although not likely, think the spring may be part of damage control or the problem depending exactly what it's function is.
___So, then the fact that my valve was not threaded completely to the bottom of the threads when I removed it (the way it is supposed to be when installed) makes no difference? I was hoping that this was the root cause of my problem.
It may be that the shaft has moved on the bearings and mis-aligned itself somehow but that is just speculation from me, hence the question for pictures ( magnus? ) because once the iacv is mounted the comparison is no longer possible, we know the iacv fails sometimes, we don't know how though, here is your opportunity to find out, all we know is the pictures magnus posted regarding his iacv replacement.
Thing to remember is that the engine ran fine for a long time when you got it, if the piston was mis-aligned ( position-wise ) it would have shown up very quickly, so something has changed some time later.
Q; does the shaft rotate freely?
If the piston is made out of plastic it may be affected by heat somehow.
Here is the spring in front of the piston;
___So does this mean that if the valve is not threaded down completely when it is installed (like mine was when I removed it) then the ECM will automatically compensate and send the proper signal to the motor to properly locate the valve?
Depending on the forces involved it may be a reason for failure, although not likely, think the spring may be part of damage control or the problem depending exactly what it's function is.
___So, then the fact that my valve was not threaded completely to the bottom of the threads when I removed it (the way it is supposed to be when installed) makes no difference? I was hoping that this was the root cause of my problem.
It may be that the shaft has moved on the bearings and mis-aligned itself somehow but that is just speculation from me, hence the question for pictures ( magnus? ) because once the iacv is mounted the comparison is no longer possible, we know the iacv fails sometimes, we don't know how though, here is your opportunity to find out, all we know is the pictures magnus posted regarding his iacv replacement.
Thing to remember is that the engine ran fine for a long time when you got it, if the piston was mis-aligned ( position-wise ) it would have shown up very quickly, so something has changed some time later.
Q; does the shaft rotate freely?
SportsterDoc
Road warrior
Two common methods of homing a stepper motor are:
1. Run to limit/end of travel switch
2. Monitor current, which will increase if run to a hard stop (see link)
Stepper Motor Sensor Less Homing
My experience is limited to industrial applications, hence the above link.
I do not know which method Honda employs.
With a 4 wire connection,1 is possible.
The schematic shows
IACV1A to ECM A6 (black/yellow)
IACV1B to ECM A7 (black/red)
IACV2A to ECM A17 (black/blue)
IACV2B to ECM A16 (black/orange)
Both circuits (black/yellow to black/red and black/blue to black/orange) have the same resistance parameters of 91-121 ohms at 77 F, so I am thinking 1 is not as likely as 2.
Does the FSM advise anything further (other than info on FSM pages 5-74, 5-75, 15-41 & 15-42)?
In possibility 1, if the switch has moved, damaged, etc., true home would be lost.
In possibility 2, if there is binding, there could be a premature higher current read.
Both of these could occur even if the stepper motor is functioning normal.
Kudos for the offer.
Dave
Did you find any carbon/crud/partial blockage in the port controlled by the IACV?
1. Run to limit/end of travel switch
2. Monitor current, which will increase if run to a hard stop (see link)
Stepper Motor Sensor Less Homing
My experience is limited to industrial applications, hence the above link.
I do not know which method Honda employs.
With a 4 wire connection,1 is possible.
The schematic shows
IACV1A to ECM A6 (black/yellow)
IACV1B to ECM A7 (black/red)
IACV2A to ECM A17 (black/blue)
IACV2B to ECM A16 (black/orange)
Both circuits (black/yellow to black/red and black/blue to black/orange) have the same resistance parameters of 91-121 ohms at 77 F, so I am thinking 1 is not as likely as 2.
Does the FSM advise anything further (other than info on FSM pages 5-74, 5-75, 15-41 & 15-42)?
In possibility 1, if the switch has moved, damaged, etc., true home would be lost.
In possibility 2, if there is binding, there could be a premature higher current read.
Both of these could occur even if the stepper motor is functioning normal.
My hat is off to you, John!Magnus_imp said:
Kudos for the offer.
Dave
Did you find any carbon/crud/partial blockage in the port controlled by the IACV?
First off, my sincere thank you to John for his very generous offer. Hopefully I will not have to call you, but it's nice to know that help is not far away. John - did you remove your rear wheel to get the fender out? Did you remove the entre throttle body assembly?
I reinstalled the battery last night and tested the old and new IACVs side-by-side. I must have cycled each one thirty times, alternating back and forth. In all honesty, I cannot detect any difference in the way they operate. But this test only checks what I believe to be only a small portion of the full operation of the IACV; I'm sure you guys who are much more knowledgeable on this topic would know how to perform a more thorough inspection.
The valve is metallic, so I assume it is aluminum. The port in the cylinder is completely clean and there is no obstruction.
My plan is to get the new IACV installed tomorrow. I will perform a valve clearance inspection while I have the tank off, but I don't know if I'll have time tomorrow to do all of this (other chores and responsibilities are calling).
Thanks again to all you guys for all of your support!
I reinstalled the battery last night and tested the old and new IACVs side-by-side. I must have cycled each one thirty times, alternating back and forth. In all honesty, I cannot detect any difference in the way they operate. But this test only checks what I believe to be only a small portion of the full operation of the IACV; I'm sure you guys who are much more knowledgeable on this topic would know how to perform a more thorough inspection.
The valve is metallic, so I assume it is aluminum. The port in the cylinder is completely clean and there is no obstruction.
My plan is to get the new IACV installed tomorrow. I will perform a valve clearance inspection while I have the tank off, but I don't know if I'll have time tomorrow to do all of this (other chores and responsibilities are calling).
Thanks again to all you guys for all of your support!
SportsterDoc
Road warrior
The FSM may not so mention, but I would be tempted to spray silicone lubricant on the IACV piston before installing.
Good luck, Dave. I will be off-line tomorrow (going to Laughlin, via Kingman and Oatman) but will log-on as soon as I get home, as I am anxious to know of your progress.
Good luck, Dave. I will be off-line tomorrow (going to Laughlin, via Kingman and Oatman) but will log-on as soon as I get home, as I am anxious to know of your progress.
Thank you Doc. I do not believe our bikes have a travel limit sensor switch, so your second option of measuring the current is probably how Honda does it. Maybe my valve got stuck at one time and this caused a higher than normal current flow that somehow disrupted the calibration (if there is a calibration) between the valve and the ECM?SportsterDoc_imp said:
I believe the FSM states to coat the valve with engine oil before installing it. What do you think about a very lite coat of grease? Would the grease potentially cause too much friction?
Magnus_imp
First service completed
I didn't have to remove the rear wheel. I kept the throttle body assembly attached. I think I posted a picture somewhere in this long, long thread.
Dave_imp said:
Lord Popgun
Road warrior
And here is Magnus’ post with the pic: CB1100 Idle speed instability problem
SportsterDoc
Road warrior
If it homes via current sensing, then getting stuck would give false feedback to the ECM. The ECM would think it did a full travel, instead of a partial travel, but we are just guessing, without knowing more about the actual ECM program.Dave_imp said:
The 4 wire, with two equal resistance circuits, indicate that the IACV uses two phase bi-polar windings: All About Stepper Motors.
Grease may be too low viscosity and my thinking is that silicone spray lubricant may last longer. Do as you are most comfortable. If silicone, then check material compatibility...some is fine with plastics, rubber, etc....some are not.Dave_imp said:
max
Road warrior
Thanks for the link popgun, looks pristene inside that throttle body.
That is something i had not considered doc, current sensing.
I think that can be simulated by holding the shaft and see if it the ecm stops prematurely on over current.
Something else that crossed my mind is; what would happen if two of the wires are reversed somehow?
remember some tail lights have the green and pink/blue wires the wrong way.
It may be a good idea to check the color of the wires in the 4 pole iacv connector and at the ecm if they are the right way around.
on the ecm;
black/yellow---a6----iacv1a
black/orange--a7----iacv2a
black/blue------a16--iacv1b
black/red--------a17--iacv2b
and on the iacv connector in the following order;
black/yellow
black/red
black/blue
black/orange
You can see that the inside pair is coil b and outside pair is coil a on the iacv.
It may well be that one side of the coils is connected to dc volts or ground and can be measured with a voltmeter for correct polarity at the disconnected iacv connector ( at any time ).
link for wiring diagram Electrical Gremlin - Clock/Trip Reset & No Blinkers and click on " here " at bottom of post.
Dave may know how much torque is produced by the stepper motor and if the shaft can rotate freely or is held in place if not energized?
If it was me i would not apply grease on the piston, dust may stick to it over time and probably too much friction inside the barrel when cold.
as far as i can tell it only makes contact in the groove of the piston so maybe a tiny amount of oil inside that groove only, remember it gets hot in there and any excess would run off, collect at the bottom of the barrel and just sit there collecting filtered dust.
And thanks for the check of the piston material Dave, when the iacv initialises does it move the piston away from the stepper motor ( out ) and then reverse toward it or the other way round?
At the end of the day Dave will have the only faulty iacv in captivity in the world.
That is something i had not considered doc, current sensing.
I think that can be simulated by holding the shaft and see if it the ecm stops prematurely on over current.
Something else that crossed my mind is; what would happen if two of the wires are reversed somehow?
remember some tail lights have the green and pink/blue wires the wrong way.
It may be a good idea to check the color of the wires in the 4 pole iacv connector and at the ecm if they are the right way around.
on the ecm;
black/yellow---a6----iacv1a
black/orange--a7----iacv2a
black/blue------a16--iacv1b
black/red--------a17--iacv2b
and on the iacv connector in the following order;
black/yellow
black/red
black/blue
black/orange
You can see that the inside pair is coil b and outside pair is coil a on the iacv.
It may well be that one side of the coils is connected to dc volts or ground and can be measured with a voltmeter for correct polarity at the disconnected iacv connector ( at any time ).
link for wiring diagram Electrical Gremlin - Clock/Trip Reset & No Blinkers and click on " here " at bottom of post.
Dave may know how much torque is produced by the stepper motor and if the shaft can rotate freely or is held in place if not energized?
If it was me i would not apply grease on the piston, dust may stick to it over time and probably too much friction inside the barrel when cold.
as far as i can tell it only makes contact in the groove of the piston so maybe a tiny amount of oil inside that groove only, remember it gets hot in there and any excess would run off, collect at the bottom of the barrel and just sit there collecting filtered dust.
And thanks for the check of the piston material Dave, when the iacv initialises does it move the piston away from the stepper motor ( out ) and then reverse toward it or the other way round?
At the end of the day Dave will have the only faulty iacv in captivity in the world.
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