Throttle hang and the Idle Stepper Table
Typically when the stepper values or desired idle RPM values have little or no effect, its due to the setting of the BISS (the base idle set screw)
Base idle should be around 750rpm or so, then the stepper does its work from there. This was a trick to raise idle speed before there was access to the settings in the ECU, or if the base idle is too low or too high and needs minor adjustment. What ends up happening is you open the BISS, and the stepper ends up completely closed in an attempt to adjust idle quality and speed, or other stepper values, and basically unable to do anything.
Base idle should be around 750rpm or so, then the stepper does its work from there. This was a trick to raise idle speed before there was access to the settings in the ECU, or if the base idle is too low or too high and needs minor adjustment. What ends up happening is you open the BISS, and the stepper ends up completely closed in an attempt to adjust idle quality and speed, or other stepper values, and basically unable to do anything.
Both Evoscan and Mitsulogger have the ability to send custom codes, but in order for the actuator codes to work, you have to send them once to enable the test, and again to turn it off. I can add this feature in the next full release but I would like to know what all of the actuator/solenoid test codes are so I could put them all in. I actually am in the process of purchasing a MUT so I can go through and get all of the tests and other communications on my bench.
Addressing the hot/cold temps and Stepper, the stepper table is the lookup reference for temp and RPM, In raising the desired idle speed, you are altering the stepper's home location. If you find it still does that, try adjusting your BISS lower as thats probably why it happens when cold and not when hot.
Addressing the hot/cold temps and Stepper, the stepper table is the lookup reference for temp and RPM, In raising the desired idle speed, you are altering the stepper's home location. If you find it still does that, try adjusting your BISS lower as thats probably why it happens when cold and not when hot.
The problem is in fact soley ECU related. I can recreate this throttle hang very consistantly. When ever I am above 3500 rpm and esspecially partial throttle it will happen. I know it is ONLY ECU related because when I slide my car out of gear without touching the clutch, the rpm's hang exactly where I left them. They will stay their forever even if I am at a complete stop. The only way to get the rpm's to come back down was to push in the clutch. I furthur looked into this by adjusting the upper clutch switch to the point of it not comming in contact with the cluth at all so that there was no activation of this switch. Sure enough when I went back out on the road, the rpm's would hang there all day even if I was using the clutch. Very frustrating indeed. Anyway, try to re-create this yourself and I guarentee you will have the same result
The problem is in fact soley ECU related. I can recreate this throttle hang very consistantly. When ever I am above 3500 rpm and esspecially partial throttle it will happen. I know it is ONLY ECU related because when I slide my car out of gear without touching the clutch, the rpm's hang exactly where I left them. They will stay their forever even if I am at a complete stop. The only way to get the rpm's to come back down was to push in the clutch. I furthur looked into this by adjusting the upper clutch switch to the point of it not comming in contact with the cluth at all so that there was no activation of this switch. Sure enough when I went back out on the road, the rpm's would hang there all day even if I was using the clutch. Very frustrating indeed. Anyway, try to re-create this yourself and I guarentee you will have the same result
It has got to be some off throttle fuel table of some sort...
The problem is in fact soley ECU related. I can recreate this throttle hang very consistantly. When ever I am above 3500 rpm and esspecially partial throttle it will happen. I know it is ONLY ECU related because when I slide my car out of gear without touching the clutch, the rpm's hang exactly where I left them. They will stay their forever even if I am at a complete stop. The only way to get the rpm's to come back down was to push in the clutch. I furthur looked into this by adjusting the upper clutch switch to the point of it not comming in contact with the cluth at all so that there was no activation of this switch. Sure enough when I went back out on the road, the rpm's would hang there all day even if I was using the clutch. Very frustrating indeed. Anyway, try to re-create this yourself and I guarentee you will have the same result
The TPS reads zero as it should, but the fuel is not being cut. It does not depend on boost pressure, i can take it up to about 3500rpm in vacuum and let off the throttle and it will have the same behavior, very repeatable, and not boost related.
It has got to be some off throttle fuel table of some sort...
It has got to be some off throttle fuel table of some sort...
I sort of have had a problem like this.
The other day while coming to a stop I heel-toe'd kinda funky and ended up just taking the car out of gear instead.. and my rpms were locked in at 4000 rpms while I was on the brakes only. It wouldn't stop until I tapped the gas.. not sure what happened. But its done this twice so far :|
The other day while coming to a stop I heel-toe'd kinda funky and ended up just taking the car out of gear instead.. and my rpms were locked in at 4000 rpms while I was on the brakes only. It wouldn't stop until I tapped the gas.. not sure what happened. But its done this twice so far :|
I am going out on a limb here so its just a guess.
Ever have a car that had a heavy stock flywheel?
Ever install a lightened flywheel on that same car?
Ever notice that the car would stall when coming off the throttle or the RPM would dip way below the normal idle speed?
I assume thats because the ISCV can react fast enough to stabilize the idle. Since the ISCV is essentially a controlled vacuum leak, it could come into effect at any point.
Mitsu used a light flywheel in the EVO from the get go. I wonder if they purposely made the ISCV operate just quick enough to prevent stalling but not quick enough to prevent the throttle hang?
Its just a guess, so feel free to correct me.
Ever have a car that had a heavy stock flywheel?
Ever install a lightened flywheel on that same car?
Ever notice that the car would stall when coming off the throttle or the RPM would dip way below the normal idle speed?
I assume thats because the ISCV can react fast enough to stabilize the idle. Since the ISCV is essentially a controlled vacuum leak, it could come into effect at any point.
Mitsu used a light flywheel in the EVO from the get go. I wonder if they purposely made the ISCV operate just quick enough to prevent stalling but not quick enough to prevent the throttle hang?
Its just a guess, so feel free to correct me.
I am going out on a limb here so its just a guess.
Ever have a car that had a heavy stock flywheel?
Ever install a lightened flywheel on that same car?
Ever notice that the car would stall when coming off the throttle or the RPM would dip way below the normal idle speed?
I assume thats because the ISCV can react fast enough to stabilize the idle. Since the ISCV is essentially a controlled vacuum leak, it could come into effect at any point.
Mitsu used a light flywheel in the EVO from the get go. I wonder if they purposely made the ISCV operate just quick enough to prevent stalling but not quick enough to prevent the throttle hang?
Its just a guess, so feel free to correct me.
Ever have a car that had a heavy stock flywheel?
Ever install a lightened flywheel on that same car?
Ever notice that the car would stall when coming off the throttle or the RPM would dip way below the normal idle speed?
I assume thats because the ISCV can react fast enough to stabilize the idle. Since the ISCV is essentially a controlled vacuum leak, it could come into effect at any point.
Mitsu used a light flywheel in the EVO from the get go. I wonder if they purposely made the ISCV operate just quick enough to prevent stalling but not quick enough to prevent the throttle hang?
Its just a guess, so feel free to correct me.
On the topic of lightened flywheels though... I had the rpm hang problem with the stock clutch as well as with the exedy twin hd that I have in now.
The idle stepper generally tries to find a home position under the conditions your describing, I have seen this happen when the BISS is open too much to compensate for idle adjustment PRIOR to our ability to adjust the Idle speed and stepper tables in the ECU.
I don't know why I find I have to repeat this particular bit of information, but has anyone checked their BISS settings, turned it down and then set it for 750rpm?
I also had a friend with an actual damaged idle stepper, it was actually bizzarre and we decided to check it for the hell of it and discovered that theres a "Plunger" type assembly that the stepper rotates inside, and the plunger moves in and out, its indexed with a slot to keep it from rotating, on his there was only one piece of the slot left, and when the motor closed all the way, it would periodically get jammed no matter how much it turned, it wouldn't do anything..
Although I'm inclined to believe that the clutch switch, and other settings contribute to throttle hang, its abnormal and not "Typical" for a car. Just because a few people see it, just leads me to believe that maybe the BISS needs to be adjusted properly.
Fast idle is the result of additional air allowed to pass into the engine.. There are only a few places where this can happen, the BISS, Idle Stepper Motor, or a Vacuum leak at the throttle body.
The conditions that people keep describing are something that reminds me of some sort of fast idle setting, obviously if it can be consistently reproduced on ALL cars of a particular year then it could be ECU settings related, but it doesnt appear to happen to everyone, just a few people.
I don't know why I find I have to repeat this particular bit of information, but has anyone checked their BISS settings, turned it down and then set it for 750rpm?
I also had a friend with an actual damaged idle stepper, it was actually bizzarre and we decided to check it for the hell of it and discovered that theres a "Plunger" type assembly that the stepper rotates inside, and the plunger moves in and out, its indexed with a slot to keep it from rotating, on his there was only one piece of the slot left, and when the motor closed all the way, it would periodically get jammed no matter how much it turned, it wouldn't do anything..
Although I'm inclined to believe that the clutch switch, and other settings contribute to throttle hang, its abnormal and not "Typical" for a car. Just because a few people see it, just leads me to believe that maybe the BISS needs to be adjusted properly.
Fast idle is the result of additional air allowed to pass into the engine.. There are only a few places where this can happen, the BISS, Idle Stepper Motor, or a Vacuum leak at the throttle body.
The conditions that people keep describing are something that reminds me of some sort of fast idle setting, obviously if it can be consistently reproduced on ALL cars of a particular year then it could be ECU settings related, but it doesnt appear to happen to everyone, just a few people.
The idle stepper generally tries to find a home position under the conditions your describing, I have seen this happen when the BISS is open too much to compensate for idle adjustment PRIOR to our ability to adjust the Idle speed and stepper tables in the ECU.
I don't know why I find I have to repeat this particular bit of information, but has anyone checked their BISS settings, turned it down and then set it for 750rpm?
I also had a friend with an actual damaged idle stepper, it was actually bizzarre and we decided to check it for the hell of it and discovered that theres a "Plunger" type assembly that the stepper rotates inside, and the plunger moves in and out, its indexed with a slot to keep it from rotating, on his there was only one piece of the slot left, and when the motor closed all the way, it would periodically get jammed no matter how much it turned, it wouldn't do anything..
Although I'm inclined to believe that the clutch switch, and other settings contribute to throttle hang, its abnormal and not "Typical" for a car. Just because a few people see it, just leads me to believe that maybe the BISS needs to be adjusted properly.
Fast idle is the result of additional air allowed to pass into the engine.. There are only a few places where this can happen, the BISS, Idle Stepper Motor, or a Vacuum leak at the throttle body.
The conditions that people keep describing are something that reminds me of some sort of fast idle setting, obviously if it can be consistently reproduced on ALL cars of a particular year then it could be ECU settings related, but it doesnt appear to happen to everyone, just a few people.
I don't know why I find I have to repeat this particular bit of information, but has anyone checked their BISS settings, turned it down and then set it for 750rpm?
I also had a friend with an actual damaged idle stepper, it was actually bizzarre and we decided to check it for the hell of it and discovered that theres a "Plunger" type assembly that the stepper rotates inside, and the plunger moves in and out, its indexed with a slot to keep it from rotating, on his there was only one piece of the slot left, and when the motor closed all the way, it would periodically get jammed no matter how much it turned, it wouldn't do anything..
Although I'm inclined to believe that the clutch switch, and other settings contribute to throttle hang, its abnormal and not "Typical" for a car. Just because a few people see it, just leads me to believe that maybe the BISS needs to be adjusted properly.
Fast idle is the result of additional air allowed to pass into the engine.. There are only a few places where this can happen, the BISS, Idle Stepper Motor, or a Vacuum leak at the throttle body.
The conditions that people keep describing are something that reminds me of some sort of fast idle setting, obviously if it can be consistently reproduced on ALL cars of a particular year then it could be ECU settings related, but it doesnt appear to happen to everyone, just a few people.
As far as i can tell it happens on all IX's. I have two other friends with them and they both have the same issue. It happened on mine when it was brand new <10 miles on the odo. I know that not everything brand new is without blemish, but the repeatablility is staggering. I don't really want to vta, but if that will solve it, i would. Perhaps I will set up a poll for peeps to vote on it and see what cars they have and what mods...stay tuned...