Throttle hang and the Idle Stepper Table
ok so I dont know if this is known information or not, but here it is. I crawled under the dash, which sucked by the way, looking for anything that would cause the behavior I described previously, regarding engine braking while slightly pushing clutch pedal. it tuns out that there is a button/switch behind the arm of the clutch pedal. when the clutch pedal is engaged slightly, enough to release cruise control(which obviously does not exist) the button pops out. the first pic is one with the pedal pushed all the way in(button released). the second pic is the clutch pedal not pushed in. (button pushed in) Any of you gurus PLEASE chime in. I am going to go look see if it can be unplugged
One button is for clutch in to start.
The other button is for a signal to ECU.
For those with throttle hang, depress the clutch pedal twice and the hang will drop.
Oh THANK GOD for this thread...
I have driven my BRAND NEW IX MR for a total of 80 miles, and within the first 10 miles I remarked about this throttle hang. I said to my friend "this flywheel must be a thousand pounds!"
My background is with Toyotas, and toyota's ECUs and programing are pretty rock solid, so the first thing I was thinking was mechanical. Here were my thoughts.
1) Heavy flywheel / rotating mass causing inertia to keep RPMs high
2) Throttle plate sticking slightly open (pressure, or friction)
3) Throttle plate doesn't seal (doubtful as idle is controlled low)
4) Stock BOV/Diverter valve not releasing pressure, causing throttle plate to stick open.
Those with you with data logging, I would love to see the following perameters:
Throttle Position
Manifold pressure
IAC position
MAF voltage
Injector percentage.
Basically, if we see throttle position not closing, then it's a mechanical problem
If we see the throttle position fully closing then it's a software problem
Lets look at the symptoms... then let's look at the cause of those... then let's look at the cause of THOSE and go from there. once we know all the causes, we can fix them.
Symptom - RPM "hangs" after throttle closes.
Cause
Theory - Inertia keeping RPMs high, Solution: lower rotating mass
Theory - injectors are being cut causing a lean condition, and a lean power increase... (HIGHLY doubtful, but still to test)
Theory - air being vented into manifold, Cause: throttle plate open? IAC open?
Test the throttle plate... what is the voltage of the throttle plate when closed and this condition occurs. If the throttle plate is fully closed, we can eliminate the Diverter valve as a problem as well...
Test the IAC... unplug it, and see if the hang is fixed
I've been reading these forums for a couple weeks now, and it seems that any time there is a problem, people use the "boomerang solution"... This means to throw a part/software change at it and see if it comes back. Lets look at the causes and fix those.
of course I would love to do these myself, however my car is in Arizona, and I am in Wisconsin for the next month... so I can't check these myself.
Good luck guys... hope I've helped somewhat here
I have driven my BRAND NEW IX MR for a total of 80 miles, and within the first 10 miles I remarked about this throttle hang. I said to my friend "this flywheel must be a thousand pounds!"
My background is with Toyotas, and toyota's ECUs and programing are pretty rock solid, so the first thing I was thinking was mechanical. Here were my thoughts.
1) Heavy flywheel / rotating mass causing inertia to keep RPMs high
2) Throttle plate sticking slightly open (pressure, or friction)
3) Throttle plate doesn't seal (doubtful as idle is controlled low)
4) Stock BOV/Diverter valve not releasing pressure, causing throttle plate to stick open.
Those with you with data logging, I would love to see the following perameters:
Throttle Position
Manifold pressure
IAC position
MAF voltage
Injector percentage.
Basically, if we see throttle position not closing, then it's a mechanical problem
If we see the throttle position fully closing then it's a software problem
Lets look at the symptoms... then let's look at the cause of those... then let's look at the cause of THOSE and go from there. once we know all the causes, we can fix them.
Symptom - RPM "hangs" after throttle closes.
Cause
Theory - Inertia keeping RPMs high, Solution: lower rotating mass
Theory - injectors are being cut causing a lean condition, and a lean power increase... (HIGHLY doubtful, but still to test)
Theory - air being vented into manifold, Cause: throttle plate open? IAC open?
Test the throttle plate... what is the voltage of the throttle plate when closed and this condition occurs. If the throttle plate is fully closed, we can eliminate the Diverter valve as a problem as well...
Test the IAC... unplug it, and see if the hang is fixed
I've been reading these forums for a couple weeks now, and it seems that any time there is a problem, people use the "boomerang solution"... This means to throw a part/software change at it and see if it comes back. Lets look at the causes and fix those.
of course I would love to do these myself, however my car is in Arizona, and I am in Wisconsin for the next month... so I can't check these myself.
Good luck guys... hope I've helped somewhat here
good bunch of theories. I will try and test whatever i can. But somethign else you should know, is that people with wide band 02s have reported that fuel is in fact being delivered when the throttle is closed. If you have read above, i have a theory about it being half mechanical and half software related. It is regarding the one clutch switch way hight up. I am going to be getting retuned either the end of the month or the begining of next month. I will ask Al if he has any insight on it.
Sooo, I have been looking at some logs where I purposly made the car go into this throttle hang thing/mode, and here is what I had found..
My car "exits" this mode at approx. 3125RPM.
I can tell because of the following values tha ECU Flash is spitting out.
(Items that change immediately when car kicks out of the throttle hang mode thingy):
O2Feedback Trim goes to 100 from whatever value it was at... Now, what I did notice is that when I let off the gas, ie. the TPS drops suddenly to between 14.1-13.7, the O2 goes to 100...
O2Sensor drops to 0 which makes sense, the fuel kicks off.
AirVol always drops to 0.
ISCSteps is always dropping to 61-58 then as soon as the car kicks out, it jumps back up high 60's-very low 70's.
InjPulseWidth drops to zero when it kicks off (Which makes sense)
BatteryVoltage always seems to jump up 0.1v. (Interesting... Might be a relay/switch/flex capacitor switching at that exact moment) then goes back to whatever voltage it was listing prior.
LoadCalc goes to negatives ~9.07
Wideband drops from ~13.7-14.7 to flatlining at 10.1 (Uhhh, OK. Don't understand this one as the pulsewidth dropped to 0, so how is the wideband reading 10.1:1??)
MAP always seems to jump up a bit, usually from roughly 58-65 and jumps to low 70's.
Now, what does all this mean?
Cliff notes in my best Spaceballs voice: We (I) ain't found $h1t.
I don't see anything in the data logs at least as far as I can see thta I can modify in ECUFash that might cure the problem. Maybe I am not looking at something, but with that data, at least I can see exactly what is changing when it kick's out of that mode, and see exactly what changes.
I imagine that someone might find something else in the ECU soon that directly relates to this throttle hang thing... But, at least with this data, it might make someone think of something, or help get a little closer to fixing/changng/eliminating it.
My car "exits" this mode at approx. 3125RPM.
I can tell because of the following values tha ECU Flash is spitting out.
(Items that change immediately when car kicks out of the throttle hang mode thingy):
O2Feedback Trim goes to 100 from whatever value it was at... Now, what I did notice is that when I let off the gas, ie. the TPS drops suddenly to between 14.1-13.7, the O2 goes to 100...
O2Sensor drops to 0 which makes sense, the fuel kicks off.
AirVol always drops to 0.
ISCSteps is always dropping to 61-58 then as soon as the car kicks out, it jumps back up high 60's-very low 70's.
InjPulseWidth drops to zero when it kicks off (Which makes sense)
BatteryVoltage always seems to jump up 0.1v. (Interesting... Might be a relay/switch/flex capacitor switching at that exact moment) then goes back to whatever voltage it was listing prior.
LoadCalc goes to negatives ~9.07
Wideband drops from ~13.7-14.7 to flatlining at 10.1 (Uhhh, OK. Don't understand this one as the pulsewidth dropped to 0, so how is the wideband reading 10.1:1??)
MAP always seems to jump up a bit, usually from roughly 58-65 and jumps to low 70's.
Now, what does all this mean?
Cliff notes in my best Spaceballs voice: We (I) ain't found $h1t.
I don't see anything in the data logs at least as far as I can see thta I can modify in ECUFash that might cure the problem. Maybe I am not looking at something, but with that data, at least I can see exactly what is changing when it kick's out of that mode, and see exactly what changes.
I imagine that someone might find something else in the ECU soon that directly relates to this throttle hang thing... But, at least with this data, it might make someone think of something, or help get a little closer to fixing/changng/eliminating it.
Evolving Member
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From: Walnut Creek CA (SF east bay area)
3500 rpm throttle hang
Just ran our fairly heavily modified Evo Monday at Laguna Seca. We have this problem and in a couple of places it effects you on the track - like at the corkscrew (turn 8) at Laguna. Most of the time you are in a much higher rev range but its a pain to know its there just the same. And if you are at 4500 to 5000 the car will not slow down as much. I try to run my last lap without hitting the brakes and its really hard to do with that thing holding the revs at 3500.
I feel sure the issue is all ecu related. It has nothing to do with the diverter valve. Its apparently just a matter of the ecu doing this for fuel/emissions purposes on 05 and later Evos. From what I've been told other newer cars do the same thing. Sure wish someone would come up with a flash fix for it.
I feel sure the issue is all ecu related. It has nothing to do with the diverter valve. Its apparently just a matter of the ecu doing this for fuel/emissions purposes on 05 and later Evos. From what I've been told other newer cars do the same thing. Sure wish someone would come up with a flash fix for it.
I can get it to happen in 1-5th, partial throttle over 3k rpm. Pressing the clutch and letting off the throttle under these circumstances cause a 500rpm jump, then a gradual decline with AFR's staying @ 14.7:1 until it drops below 3100rpm.
Last night, I set open loop thresholds low enough that it was in open loop the entire time, even at idle. The symptoms were much more pronounced, to the point that it it felt like there was a 1 second delay from when I let off the throttle until the throttle plate actually closed.
Here's a screenshot. 4th gear (I think) WOT until 4300rpm, rpm continues to spike until 4700rpm, AFR remains avg. 13:1 until 3000rpm, where it then shows engine braking.
Actually in your case it probably is the Diverter valve.. If I run my HKS Valve I get the RPM hang/climb, when I run a forge valve, it doesnt happen at all.
There are two unique issues going on here. They seem similar but their not. Excess pressure in the intercooler pipe will cause this to happen, the HKS does produce this on my car. When I remove it, it goes away.
There are two unique issues going on here. They seem similar but their not. Excess pressure in the intercooler pipe will cause this to happen, the HKS does produce this on my car. When I remove it, it goes away.
Evolving Member
iTrader: (4)
Joined: Mar 2003
Posts: 124
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From: Walnut Creek CA (SF east bay area)
If you have a pre 2005/6 Evo and experience this problem then perhaps its the diverter valve. But if you have a 2005/6 model its the ecu causing the hang up (unless you also have a diverter valve issue). As I recall my 2005 did this when it was totally stock, and I assume all 2005/6 models do it. I've had several different diverter valves on mine and they make no difference at all with this 3500 rpm hang up issue. Isn't there someone out there who knows ecu technology and understands how car makers are incorporating these features into new cars to deal with fuel/emissions issues? Seems like there should be a way to flash around the issue. Any help greatly appreciated.
Last edited by tuner; Apr 12, 2007 at 07:05 AM.
Evolved Member
Joined: Feb 2006
Posts: 1,345
Likes: 1
From: MA
Sooo, I have been looking at some logs where I purposly made the car go into this throttle hang thing/mode, and here is what I had found..
My car "exits" this mode at approx. 3125RPM.
I can tell because of the following values tha ECU Flash is spitting out.
(Items that change immediately when car kicks out of the throttle hang mode thingy):
O2Feedback Trim goes to 100 from whatever value it was at... Now, what I did notice is that when I let off the gas, ie. the TPS drops suddenly to between 14.1-13.7, the O2 goes to 100...
O2Sensor drops to 0 which makes sense, the fuel kicks off.
AirVol always drops to 0.
ISCSteps is always dropping to 61-58 then as soon as the car kicks out, it jumps back up high 60's-very low 70's.
InjPulseWidth drops to zero when it kicks off (Which makes sense)
BatteryVoltage always seems to jump up 0.1v. (Interesting... Might be a relay/switch/flex capacitor switching at that exact moment) then goes back to whatever voltage it was listing prior.
LoadCalc goes to negatives ~9.07
Wideband drops from ~13.7-14.7 to flatlining at 10.1 (Uhhh, OK. Don't understand this one as the pulsewidth dropped to 0, so how is the wideband reading 10.1:1??)
MAP always seems to jump up a bit, usually from roughly 58-65 and jumps to low 70's.
Now, what does all this mean?
Cliff notes in my best Spaceballs voice: We (I) ain't found $h1t.
I don't see anything in the data logs at least as far as I can see thta I can modify in ECUFash that might cure the problem. Maybe I am not looking at something, but with that data, at least I can see exactly what is changing when it kick's out of that mode, and see exactly what changes.
I imagine that someone might find something else in the ECU soon that directly relates to this throttle hang thing... But, at least with this data, it might make someone think of something, or help get a little closer to fixing/changng/eliminating it.
My car "exits" this mode at approx. 3125RPM.
I can tell because of the following values tha ECU Flash is spitting out.
(Items that change immediately when car kicks out of the throttle hang mode thingy):
O2Feedback Trim goes to 100 from whatever value it was at... Now, what I did notice is that when I let off the gas, ie. the TPS drops suddenly to between 14.1-13.7, the O2 goes to 100...
O2Sensor drops to 0 which makes sense, the fuel kicks off.
AirVol always drops to 0.
ISCSteps is always dropping to 61-58 then as soon as the car kicks out, it jumps back up high 60's-very low 70's.
InjPulseWidth drops to zero when it kicks off (Which makes sense)
BatteryVoltage always seems to jump up 0.1v. (Interesting... Might be a relay/switch/flex capacitor switching at that exact moment) then goes back to whatever voltage it was listing prior.
LoadCalc goes to negatives ~9.07
Wideband drops from ~13.7-14.7 to flatlining at 10.1 (Uhhh, OK. Don't understand this one as the pulsewidth dropped to 0, so how is the wideband reading 10.1:1??)
MAP always seems to jump up a bit, usually from roughly 58-65 and jumps to low 70's.
Now, what does all this mean?
Cliff notes in my best Spaceballs voice: We (I) ain't found $h1t.
I don't see anything in the data logs at least as far as I can see thta I can modify in ECUFash that might cure the problem. Maybe I am not looking at something, but with that data, at least I can see exactly what is changing when it kick's out of that mode, and see exactly what changes.
I imagine that someone might find something else in the ECU soon that directly relates to this throttle hang thing... But, at least with this data, it might make someone think of something, or help get a little closer to fixing/changng/eliminating it.