Throttle hang and the Idle Stepper Table
Jan 14, 2007, 08:18 AM
#46
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Maybe what i am experienceing is a little different. After a WOT pull i may let of the gas at any given RPM. Usualy above say 4k, the car fells like the cruise control is on. I get no engine braking and it will just continue to cruse along at that RPM. Its defenetly not a stuck throttle cable BTW.
i get the same exact thing. i have found that when it happens if you push in the clutch peddle again it will make the revs drop to the normal level. try that and see if it works for you too. if thats the case it might have something to do with the clutch position sensor if we have one of those.
Jan 15, 2007, 08:17 AM
#47
Dont know if this is related but same symptom - When I was rigging stuff in order to get my DV holding solid to redline in between shifts it gets overloaded with air (especially at 26 psi). DV opens but not in time, so when I lift the throttle the air forces it back open and a good portion VTE's (vents to engine) making the rpm peg the rev limit between shifts durring high boost and cold days.
One little additional spring to the TB (two in there, added a third) was enough to overcome the additional air that pushed it beyond it's design. So now - no more involuntary RPM blips between shifts - I was starting to get so frustrated with it that I was going to give up the top end boost to make it quit.
Now the car is so much fun to drive I have to make excuses to my wife for grocery shopping so I can go to get to drive it.
One little additional spring to the TB (two in there, added a third) was enough to overcome the additional air that pushed it beyond it's design. So now - no more involuntary RPM blips between shifts - I was starting to get so frustrated with it that I was going to give up the top end boost to make it quit.
Now the car is so much fun to drive I have to make excuses to my wife for grocery shopping so I can go to get to drive it.
I think i may have to give this a shot! Do you have any pictures of where the springs are located. What else could hold the revs up right. It has to be air getting past the TB. Its not fly by wire ! The ecu cant open the throttle right?
Jan 15, 2007, 09:33 AM
#49
Dont know if this is related but same symptom - When I was rigging stuff in order to get my DV holding solid to redline in between shifts it gets overloaded with air (especially at 26 psi). DV opens but not in time, so when I lift the throttle the air forces it back open and a good portion VTE's (vents to engine) making the rpm peg the rev limit between shifts durring high boost and cold days.
One little additional spring to the TB (two in there, added a third) was enough to overcome the additional air that pushed it beyond it's design. So now - no more involuntary RPM blips between shifts - I was starting to get so frustrated with it that I was going to give up the top end boost to make it quit.
Now the car is so much fun to drive I have to make excuses to my wife for grocery shopping so I can go to get to drive it.
One little additional spring to the TB (two in there, added a third) was enough to overcome the additional air that pushed it beyond it's design. So now - no more involuntary RPM blips between shifts - I was starting to get so frustrated with it that I was going to give up the top end boost to make it quit.
Now the car is so much fun to drive I have to make excuses to my wife for grocery shopping so I can go to get to drive it.
Jan 17, 2007, 08:04 AM
#51
While some of the fixes here are probably valid on more modified cars with other issues, i have to disagree for the most part.
My car has tbe, mbc, reflash/custom tune diy. ('06 RS)
It has had this symptom since it was brand new - 7 miles on the odo.
It is very consistant and i can recreate it anytime.
Anytime i am on throttle and lift anywhere above 3500 rpms, it will continue to "hang" and not engine brake until it gets down below 3000-3500 rpms, then it will engine brake as it should. I do not believe it is a dv or bov or iacv or any of the aux valves, because there is still fuel being delivered in this situation.
Any of you that have wb's, check the afr's next time you have this issue, it will read 14.7:1. It should read 21:1 or however lean your wb will register.
So, basically, the ecu is delivering fuel. I figure there is only a few things that could make this happen:
Due to the fact that fuel is still being delivered is my main reason for blaming the ecu for this problem. Lets get it figured out so the next track day my brakes dont have to fight off throttle fuel delivery.
My car has tbe, mbc, reflash/custom tune diy. ('06 RS)
It has had this symptom since it was brand new - 7 miles on the odo.
It is very consistant and i can recreate it anytime.
Anytime i am on throttle and lift anywhere above 3500 rpms, it will continue to "hang" and not engine brake until it gets down below 3000-3500 rpms, then it will engine brake as it should. I do not believe it is a dv or bov or iacv or any of the aux valves, because there is still fuel being delivered in this situation.
Any of you that have wb's, check the afr's next time you have this issue, it will read 14.7:1. It should read 21:1 or however lean your wb will register.
So, basically, the ecu is delivering fuel. I figure there is only a few things that could make this happen:
Due to the fact that fuel is still being delivered is my main reason for blaming the ecu for this problem. Lets get it figured out so the next track day my brakes dont have to fight off throttle fuel delivery.
Jan 17, 2007, 08:14 AM
#52
In your case, have you ever replaced or removed the stock DV? I had several members mention some weird issues, I recall one or two had the RPM's rise between shifts, but never throttle hang, but the one thing I found fixed the issue on their stock cars was their factory DV was on backwards from the factory, basically it required significantly more vacuum to open the valve and would cause the RPM's to rise when the pressure would not vent properly and the addional pressurized air would sneak past the idle control or Biss.
This "hang" would make sense as the Stepper would be altering its settings by opening and closing to its set point, while there is still pressurized air going through there.
This "hang" would make sense as the Stepper would be altering its settings by opening and closing to its set point, while there is still pressurized air going through there.
Jan 17, 2007, 08:25 AM
#53
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Interesting. I'm going to check my DV position right now. I would have never expected it to be installed backwards from the factory. I have the same issue with my '06 RS. Even standing still, if I hit the throttle, the rpms take forever to drop. Never had an issue with my '03. It does seem to drop quicker with the clutch pushed in.
Jan 17, 2007, 09:10 AM
#55
While some of the fixes here are probably valid on more modified cars with other issues, i have to disagree for the most part.
My car has tbe, mbc, reflash/custom tune diy. ('06 RS)
It has had this symptom since it was brand new - 7 miles on the odo.
It is very consistant and i can recreate it anytime.
Anytime i am on throttle and lift anywhere above 3500 rpms, it will continue to "hang" and not engine brake until it gets down below 3000-3500 rpms, then it will engine brake as it should. I do not believe it is a dv or bov or iacv or any of the aux valves, because there is still fuel being delivered in this situation.
Any of you that have wb's, check the afr's next time you have this issue, it will read 14.7:1. It should read 21:1 or however lean your wb will register.
So, basically, the ecu is delivering fuel. I figure there is only a few things that could make this happen:
Due to the fact that fuel is still being delivered is my main reason for blaming the ecu for this problem. Lets get it figured out so the next track day my brakes dont have to fight off throttle fuel delivery.
My car has tbe, mbc, reflash/custom tune diy. ('06 RS)
It has had this symptom since it was brand new - 7 miles on the odo.
It is very consistant and i can recreate it anytime.
Anytime i am on throttle and lift anywhere above 3500 rpms, it will continue to "hang" and not engine brake until it gets down below 3000-3500 rpms, then it will engine brake as it should. I do not believe it is a dv or bov or iacv or any of the aux valves, because there is still fuel being delivered in this situation.
Any of you that have wb's, check the afr's next time you have this issue, it will read 14.7:1. It should read 21:1 or however lean your wb will register.
So, basically, the ecu is delivering fuel. I figure there is only a few things that could make this happen:
Due to the fact that fuel is still being delivered is my main reason for blaming the ecu for this problem. Lets get it figured out so the next track day my brakes dont have to fight off throttle fuel delivery.
This is exactly what i am experiencing!
Jan 17, 2007, 01:56 PM
#57
Sorry people for time lapse.
Here's the scoop, in my case at least. In order for me to push the boost holding of the DV to the max I rigged a contraption that basically vents the air underneath DV diaghram through an internal port I added.
The solenoid which basically closes the port between shifts is not openeing fast enough so there is about a 0.5 sec lag in time. The air is trapped on the charge assembly long enough to overcome the TB springs. Even though foot is off throttle the forward direction of air is felt at the MAF as if it was floored.
I have a spare intake manifold/TB assy with all the attached solenoids (garbage for some, my treasure
) laying around and I cannibalized one of the two TB springs and I managed to retrofit it to the two existing springs.
My original attemp on this fix was for troubleshooting purposes only and even though I'm totally satisfied with it as is, I'm going to have to eventually come up with a more technically sound and permanent fix to the spring tension, like a thicker guage spring. Nonetheless, the car is so much more fun to drive.
Just a caution: Keep in mind that adding a spring to that area can cause the throttle to stick wide open if it's intalled in such away that it may get stuck, and it's not really a fix as yet - just a diagnosis
Also keep in mind that throttle hang can be caused by other things other than what I was experiencing with my highly rigged and modestly modified stock turbo evo at 27 psi boost. The 2005 evo's were known to have a between shift rpm maintaining system built into it for some insane reason. So make sure it isnt that first
Here's the scoop, in my case at least. In order for me to push the boost holding of the DV to the max I rigged a contraption that basically vents the air underneath DV diaghram through an internal port I added.
The solenoid which basically closes the port between shifts is not openeing fast enough so there is about a 0.5 sec lag in time. The air is trapped on the charge assembly long enough to overcome the TB springs. Even though foot is off throttle the forward direction of air is felt at the MAF as if it was floored.
I have a spare intake manifold/TB assy with all the attached solenoids (garbage for some, my treasure
) laying around and I cannibalized one of the two TB springs and I managed to retrofit it to the two existing springs.My original attemp on this fix was for troubleshooting purposes only and even though I'm totally satisfied with it as is, I'm going to have to eventually come up with a more technically sound and permanent fix to the spring tension, like a thicker guage spring. Nonetheless, the car is so much more fun to drive.
Just a caution: Keep in mind that adding a spring to that area can cause the throttle to stick wide open if it's intalled in such away that it may get stuck, and it's not really a fix as yet - just a diagnosis
Also keep in mind that throttle hang can be caused by other things other than what I was experiencing with my highly rigged and modestly modified stock turbo evo at 27 psi boost. The 2005 evo's were known to have a between shift rpm maintaining system built into it for some insane reason. So make sure it isnt that first
Last edited by C6C6CH3vo; Jan 17, 2007 at 02:03 PM.
Jan 17, 2007, 02:21 PM
#58
Sorry people for time lapse.
Here's the scoop, in my case at least. In order for me to push the boost holding of the DV to the max I rigged a contraption that basically vents the air underneath DV diaghram through an internal port I added.
The solenoid which basically closes the port between shifts is not openeing fast enough so there is about a 0.5 sec lag in time. The air is trapped on the charge assembly long enough to overcome the TB springs. Even though foot is off throttle the forward direction of air is felt at the MAF as if it was floored.
I have a spare intake manifold/TB assy with all the attached solenoids (garbage for some, my treasure ) laying around and I cannibalized one of the two TB springs and I managed to retrofit it to the two existing springs.
My original attemp on this fix was for troubleshooting purposes only and even though I'm totally satisfied with it as is, I'm going to have to eventually come up with a more technically sound and permanent fix to the spring tension, like a thicker guage spring. Nonetheless, the car is so much more fun to drive.
Just a caution: Keep in mind that adding a spring to that area can cause the throttle to stick wide open if it's intalled in such away that it may get stuck, and it's not really a fix as yet - just a diagnosis
Also keep in mind that throttle hang can be caused by other things other than what I was experiencing with my highly rigged and modestly modified stock turbo evo at 27 psi boost. The 2005 evo's were known to have a between shift rpm maintaining system built into it for some insane reason. So make sure it isnt that first
Here's the scoop, in my case at least. In order for me to push the boost holding of the DV to the max I rigged a contraption that basically vents the air underneath DV diaghram through an internal port I added.
The solenoid which basically closes the port between shifts is not openeing fast enough so there is about a 0.5 sec lag in time. The air is trapped on the charge assembly long enough to overcome the TB springs. Even though foot is off throttle the forward direction of air is felt at the MAF as if it was floored.
I have a spare intake manifold/TB assy with all the attached solenoids (garbage for some, my treasure
) laying around and I cannibalized one of the two TB springs and I managed to retrofit it to the two existing springs.My original attemp on this fix was for troubleshooting purposes only and even though I'm totally satisfied with it as is, I'm going to have to eventually come up with a more technically sound and permanent fix to the spring tension, like a thicker guage spring. Nonetheless, the car is so much more fun to drive.
Just a caution: Keep in mind that adding a spring to that area can cause the throttle to stick wide open if it's intalled in such away that it may get stuck, and it's not really a fix as yet - just a diagnosis
Also keep in mind that throttle hang can be caused by other things other than what I was experiencing with my highly rigged and modestly modified stock turbo evo at 27 psi boost. The 2005 evo's were known to have a between shift rpm maintaining system built into it for some insane reason. So make sure it isnt that first
Jan 19, 2007, 03:25 PM
#59
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FYI, I can simulate this behavior on my car if I bump the desired idle RPM values too high (especially in the lower temperature ranges). I have no idea why this seems to have that effect, but I've used it to effectively "tune" how much/fast the rpms drop between shifts. Weird, eh?
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