Throttle cable adjustment
#1
11-22-2016, 10:33 AM
Throttle cable adjustment
My car: White 2001 XKR convertible needed adjustment.
This is a compilation of throttle cable adjustment info from different contributors in this forum. All these are to be thanked for their input for the benefit of all the rest of us. I don't know if this info will work on your car or not. Use at your own risk.
THROTTLE CABLE ADJUSTMENT
Hlgeorge 7-04-2010 #41
How to adjust the4.0 engine. (Left hand drive)
The 4.0 engine is a little different to adjust and easierit may seem. (Mine is the R model, but I assume the standard is similar)
The location of the cable and adjustment is not under the small cover, but attached to the left side of the throttle body.
Now you can pull back on the throttle by using your thumb on the post on theoutside throttle pulley. When you let go, you should hear the metal to metalcontact of the pulley as it snaps back into idle position. This is important toremember. There is a cable strap holding the throttle cable in the cablebracket. Clip the cable strap and remove it. (Be sure you have a replacementhandy.) You can grab the throttle cable with two fingers and lift it up anddown to see if there is slack in the cable. Now, grab the throttle cable oneach side of the bracket with two fingers and lift straight up. Notice that thecable sheath is like a screw and the bracket attachment is like a nut on ascrew. Turn the bracket attachment a few turns so that the cable goes to therear of the car and snap it back in place. Feel the tension on the cable. Pullthe throttle back with the outside pulley and let it go. If you hear the metalto metal contact when you release the the pulley the cable is not too tight.You may want to over adjust the cable and move the cable back by 1/4 turn ofthe bracket attachment until you hear the metal to metal contact when thepulley is released.
My cable is`adjusted and the cable tie reinstalled. I didn't have a blackone handy, so I used a white one. If this bugs me later on, I'll replace thewhite one with a black one.
WHAT I HAVE NOTICED:
The accelerator pedal is instant. (No more tapping on it to the beat of themusic!)
Now I understand the the reason behind starting off in 2nd gear on the R model.I do not have to press as far to get the car up to speed.
In sport mode, the throttle response is instant!
Downshifts seem to be quicker, probably because I am not pressing the pedal asfar to get the car going.
On hard acceleration the car seemed to run out of torque in the upper rpmrange, but now it feels like it is pulling hard until the throttle is released.
Kevo1 07/08/2010 #62
All, Thought I would take a look at this as well becausemine an old 1997 model 4.0 was I thought sluggish for such a fine tunedvehicle. On reading the entire message I found the old XK version just hascable and a small black mounting bracket on the throttle body, with the cableattached to a cam and two nuts to lock it in place. Sure enough on having thepedal pressed all the way to the floor the cam on the throttle body was nottouching the upper stop by ¾ inch, on releasing the pedal, the protruding wireportion of the cable was found loose. To adjust it was case of loosening the13mm nuts and adjusting until the slack was removed being carful not to liftthe cam off the lower idle stop, I moved the cable about 5/16 inch.
Once complete and the nut tightened car was checked for idle speed and thentested on the road, what a difference the car just took off, no hesitation andthe gears seemed to just flow from low to high without any lag.
ShaneIam 7-18-2010 #69
98 XJ VDP owner here. I ran across this thread andfinally got around to checking mine. At 38k mi I wasn't sold on the idea thatthe cable would've stretched much, but I figured I should check it anyway. Sureenough, with the pedal completely depressed (floored), the position sensor wasonly ~80% to the upper stop. There didn't seem to be much slack, but I figured,what the heck I'll try adjusting it. Well, I found I could adjust the cable toget the pedal to open the throttle completely, but when I did so, the throttlewouldn't return to its normal "idle" position. Hmmm. Well, I guessthe only thing left to check is the pedal. Bingo: the pedal stop was screwed inuntil it was tight, but the carpet was just slightly out of line which meantthat the pedal stop was not screwed in far enough. So I pushed on the carpetand screwed the pedal stop in the rest of the way. And then took the car for aquick (pun intended) test drive. :-)
Stremsjg 8/22/2010 #104
I always thought that the slow throttle responsiveness onmy 2001 XKR was due to the throttle body being dirty or something. Well today Idecided to make change to my throttle cable. After removing the zip tie Ipopped the square off the bracket turned one turn counterclockwise and insertedthe square back into the bracket and attached a new zip tie. I started the carand took it out for a drive and was amazed at the difference. Gone was theslack in the pedal at very low speed, instead the car was immediately veryresponsive. It definately solved the problem I had with the car since I purchasedit in 2008. Now I am kicking my self for not doing the job sooner. At first Ithought the change had raised the RPM, but after the car was warmed up itsettle down to the normal 600 rpm at idle range. If I can do this job trust meanyone can. You won't be dissappointed.
WhiteXKR 3-18-2011 #189
Don't forget most OBDII readers will report throttle%...any easy way to see what is really going on.
Avos 11-14-2011 #195
What is different to 4.0 cars, is that you can extendedit so that the cable becomes too tight (so to short), and due the pin/lockingmechanism being made in such a way that it allows to slip a nodge when you overtension the cable making it adjust itself. This way you can never over tightenthe cable, and always get a perfect fit.
Avos 5-23-2012 #223
4.0 (AJ26) = only idle and torque reductions (closing thebutterfly) are controlled by the ECU, sortoff semi drive by wire.
4.0 (AJ27) = full drive by wire, but added mechanical limp home function (iircfor only 30% max open at 100% pedal down).
4.2 2003-2006 = full drive by wire, no mechanical link anymore, limp home isalso electronically controlled.
All 3 have a cable attached from the gas pedal to a Pedal positioning sensor,but on the 4.2 it is not attached anymore to the TB so also no mechanical linkanymore.
Cerberus66 5-24-2012 #225 & #226
Basic operation:
1. The accel pedal is the input
2. The engine computer receives this signal and drives the throttle motor(output)
3. The engine computer uses the throttle position sensor as feedback to confirmthe throttle position achieved.
Note:
In the following, "a failsafe" refers to action (such as shutting offpower to the throttle motor or performing fuel cut) taken to ensure safety.
Redundancies on the hardware side:
-Two separate sensor circuits in the accel pedal.
-Two separate circuits to and from the engine computer.
-Separate +5V power supplies and grounds are used for these circuits.
-Two separate sensor circuits in the throttle position sensor.
-Two separate sensor signal circuits to and from the engine computer.
-A pair of springs that close the throttle immediately if power is lost (Thethrottle closer spring is the stronger of the two. The throttle opener springopens the throttle a few degrees to prevent it from freezing closed.)
-Redundant power supplies to the engine computer.
-Multiple CPUs in the engine computer that are making the same calculations,and a watchdog function. (This ensures that the computer doesn't start making'bad decisions'.
-Multiple transistors that must operate in cooperation to power the throttlemotor (no single 'stuck' transistor can cause the throttle motor to open).
Redundancies/failsafes on the control side:
-The input section compares the two signals received from the accelerator pedalsensor. There must always be a fixed voltage relationship between the twosignal wires. If there is an out of spec difference, the MIL illuminates and afailsafe mode begins. (See the following diagram)
-With the separate CPUs/RAM, the watchdog monitors for calculation differencesand if there is a difference, the MIL illuminates and a failsafe mode begins.
-The engine computer controls a set of transistors to operate the throttlemotor. The engine computer monitors voltage and current flow. If either voltageor current is out of spec, or occurs at an improper time, then the MILilluminates and a failsafe mode begins.
-The engine computer monitors the throttle position sensor to confirm theposition of the throttle. If it is not responding correctly, then the MILilluminates and a failsafe mode begins.
-In addition to the types of monitoring mentioned above, the engine computeralso monitors each of the input and output lines for logical inconsistencies,and open and short circuits.
#226
The Throttle By-Wire (TBW) aka Drive-By-Wire (DBW)systems appears to be more complex than they actually are due the theredundancy which is built into the systems for safety reasons. Most TBW systemscontain four major components; (1) the Throttle Actuator Control Relay, (2) theDrive Circuit for the throttle actuator which is located inside the ECU, (3)the Accelerator Pedal Position (APP) assembly, and (4) the Electric ThrottleBody Assembly. With the implementation of the TBW system, manufacturers wereable to eliminate the Idle Air Control (IAC) system because they are able touse the electronic throttle body to control the engine's deceleration and idle.The below diagram will demonstrate the basic TBW system operation, pleasenotice that each sensory component of the TBW system has 6 wires connected toit; we will later explain what each of these wires are for.
The first part of this system is the Throttle Actuator Control Relay whichpowers and protects the TBW circuity. The second part of this system is theAccelerator Pedal Position (APP) assembly which transmits two pedal positioninputs to the ECU. The gas pedal (APP assembly) is effectively two independentpedal position sensors which each contain a +5V reference, a ground reference,and a signal which is sent to the TBW circuitry located inside the ECU. Onesignal is considered the “Main” APP signal and the secondary signal isconsidered the “Sub" APP signal, both of which tell the ECU what thedriver's foot is doing as far as requesting torque from the motor (how much thedriver is pushing down on the gas pedal).
The next part of this system is the Electric Throttle Body Assembly whichconsists of the throttle actuator motor, throttle valve, and 2 throttleposition sensors. Like the APP assembly this part contains 6 wires; two ofwhich are the shared +5V reference and shared ground reference wires whichpower the two TPS sensors, The next two wires are the redundant TPS sensorsignals (Main and Sub) which transmit the position of the throttle blade to theECU. The last two wires are for the throttle actuator control signal, theselines control the opening and closing of the throttle blade.
The last part of this system is the TBW Circuitry located inside the ECU. Thiscircuitry receives the Main and Sub APP signals so it knows what the driver'sfoot is doing (as far as requesting torque) then it sends a square wave, 12volt signal across the two throttle actuator control signal lines to step thethrottle actuator motor with a duty cycle; 100% duty cycle would open thethrottle blade to WOT & 0% duty cycle would keep the throttle blade at thefully closed position. Based on the feedback received from the two TPS sensorsignals located in the Electric Throttle Body Assembly, the TBW system isconstantly receiving inputs (APP & TPS) and controlling outputs (throttleactuator motor) in order to control the throttle blade movement on the vehicle.
What this means to you:
...most modern engines will never show a 0% TPS since the throttle blade isalways kept open (by 2-7%) to start the engine and to maintain idle.
...some modern engines will never report a 100% TPS while at WOT since theirTBW system may have been programmed to only open up to a predetermined point.
...you can be able to change the Rev Limits on an engine by tricking the ECUabout the reported RPM but you may not be able to get the motor to acceleratepast a certain RPM since the throttle body has been programmed to close by apredetermined RPM.
...porting of most modern throttle bodies is not a good idea unless you havethe ability to fully re-calibrate that system.
...most modern engines will not allow the motor to start immediately after thebattery has been disconnected then re-connected or if the ECU has been re-setbecause the systems needs approximately 5 seconds to fully calibrate the TBWsystem. If the battery has been disconnected then re-connected or if the ECUhas been re-set, please allow the key to stay in the ON position for a minimumof 10 seconds to allow the TBW system to calibrate before you try to start theengine.
...providing a constant +12V to the throttle actuator motor will fully open thethrottle blade, providing a constant -12V (reversing the polarity) to thethrottle actuator motor will fully close the throttle blade.
...most modern EMS logic has been calibrated to control the throttle bladeopening and closing speed. We have seen where the throttle blade actually opensslower if you slap down the gas pedal versus gradually depressing the gaspedal.
...most modern EMS programming was established to lessen the emissions outputof the motors, so throttle opening and closing delays have been implemented tolessen the emission output of the motors...not to **** you off.
...most modern vehicles have some sort of Traction Control System which use theElectric Throttle Bodies to control engine torque output.
...most modern vehicles have some artificial throttle response programmed intotheir control. For instance, if the driver is pushing down on the APP 20% the TPSsensor may report a 50% reading. The ECU is creating artificial throttleresponse by opening the throttle valve much more that the driver is requesting.
#227
AVOS help me out here. My 2000 XKR according to yournotes is a AJ27S? or AJ26?
My throttle body butterfly valve is directly connected to my throttle pedal.Can you show me through the JTIS the drive by wire components?
Avos 5-24-2012 #228
You have indeed AJ27 engine, so the throttle is operatedby the ECU, ie drive by wire.
#232
As said, on the AJ27 engines,you have fail safe mode, so the axle is connected to the butterfly so you canoperate it but only for 30% max opening or so (which is pedal to the floor).
You don’t have to take my word for it, so just try it yourself. Have a look atthe butterfly and move the cable to 100% pedal to the floor.
Paul Pavlik 5-25-2012 #239
The Accelerator Cable is connected to a DualPotentiometer Assembly AND a Fail Safe Linkage.
Normally the Potentiometer Signals are used to tell the ECM to open or closethe Throttle Plate. The Fail Safe Linkage does NOT contact the Throttle Platedirectly.
If the Throttle Motor Fails, the Fail Safe Linkage comes into play and DOESConnect to the Throttle Plate Mechanically.
There is a Rotational Lag (in Degrees of Rotation) between the Fail SafeLinkage and the Throttle Plate Shaft Assembly.
This Lag is maintained during normal operation.
In Fail Safe Mode, this Rotational Lag must be taken up before the Fail SafeLinkage contacts the Throttle Plate.
This Lag is subtracted from the Maximum Possible Rotation of the ThrottlePlate, Limiting Throttle opening in Fail Safe Mode.
Red1bw 5-25-12 #240
After resetting Throttle Body Cable I would think onethen would need to reset the following:
Resetting kickdown travel limits
After battery reconnection, the engine management system must ‘re-learn’ thelimits of throttle pedal travel. This is to ensure correct adaptive settingsare stored for kickdown operation. Re-programming is done with the ignitionswitch in position II a follows:
• Slowly press the accelerator pedal fully through the kickdown detent to thefloor. Release the pedal and repeat the action.
Giandanielxk8 5-16-2015 #297
On my car, a 2000 XK8 the adjustment is done as so:
1. Geta friend to mash the throttle and then check for slack.
2. Removescrews circled in red.
3. Spinthe tab that holds the throttle cable around the metal sheath (yellow) untilyou tighten the slack. It's like spinning a bolt on a screw.
4. Retightenthe bolts in red that were removed. You may notice that when tightening thosebolts the throttle cable is tightened just a bit more. Make sure to check againthe throttle position percentage at WOT. It is easy to remove too much slack.
This is a compilation of throttle cable adjustment info from different contributors in this forum. All these are to be thanked for their input for the benefit of all the rest of us. I don't know if this info will work on your car or not. Use at your own risk.
THROTTLE CABLE ADJUSTMENT
Hlgeorge 7-04-2010 #41
How to adjust the4.0 engine. (Left hand drive)
The 4.0 engine is a little different to adjust and easierit may seem. (Mine is the R model, but I assume the standard is similar)
The location of the cable and adjustment is not under the small cover, but attached to the left side of the throttle body.
Now you can pull back on the throttle by using your thumb on the post on theoutside throttle pulley. When you let go, you should hear the metal to metalcontact of the pulley as it snaps back into idle position. This is important toremember. There is a cable strap holding the throttle cable in the cablebracket. Clip the cable strap and remove it. (Be sure you have a replacementhandy.) You can grab the throttle cable with two fingers and lift it up anddown to see if there is slack in the cable. Now, grab the throttle cable oneach side of the bracket with two fingers and lift straight up. Notice that thecable sheath is like a screw and the bracket attachment is like a nut on ascrew. Turn the bracket attachment a few turns so that the cable goes to therear of the car and snap it back in place. Feel the tension on the cable. Pullthe throttle back with the outside pulley and let it go. If you hear the metalto metal contact when you release the the pulley the cable is not too tight.You may want to over adjust the cable and move the cable back by 1/4 turn ofthe bracket attachment until you hear the metal to metal contact when thepulley is released.
My cable is`adjusted and the cable tie reinstalled. I didn't have a blackone handy, so I used a white one. If this bugs me later on, I'll replace thewhite one with a black one.
WHAT I HAVE NOTICED:
The accelerator pedal is instant. (No more tapping on it to the beat of themusic!)
Now I understand the the reason behind starting off in 2nd gear on the R model.I do not have to press as far to get the car up to speed.
In sport mode, the throttle response is instant!
Downshifts seem to be quicker, probably because I am not pressing the pedal asfar to get the car going.
On hard acceleration the car seemed to run out of torque in the upper rpmrange, but now it feels like it is pulling hard until the throttle is released.
Kevo1 07/08/2010 #62
All, Thought I would take a look at this as well becausemine an old 1997 model 4.0 was I thought sluggish for such a fine tunedvehicle. On reading the entire message I found the old XK version just hascable and a small black mounting bracket on the throttle body, with the cableattached to a cam and two nuts to lock it in place. Sure enough on having thepedal pressed all the way to the floor the cam on the throttle body was nottouching the upper stop by ¾ inch, on releasing the pedal, the protruding wireportion of the cable was found loose. To adjust it was case of loosening the13mm nuts and adjusting until the slack was removed being carful not to liftthe cam off the lower idle stop, I moved the cable about 5/16 inch.
Once complete and the nut tightened car was checked for idle speed and thentested on the road, what a difference the car just took off, no hesitation andthe gears seemed to just flow from low to high without any lag.
ShaneIam 7-18-2010 #69
98 XJ VDP owner here. I ran across this thread andfinally got around to checking mine. At 38k mi I wasn't sold on the idea thatthe cable would've stretched much, but I figured I should check it anyway. Sureenough, with the pedal completely depressed (floored), the position sensor wasonly ~80% to the upper stop. There didn't seem to be much slack, but I figured,what the heck I'll try adjusting it. Well, I found I could adjust the cable toget the pedal to open the throttle completely, but when I did so, the throttlewouldn't return to its normal "idle" position. Hmmm. Well, I guessthe only thing left to check is the pedal. Bingo: the pedal stop was screwed inuntil it was tight, but the carpet was just slightly out of line which meantthat the pedal stop was not screwed in far enough. So I pushed on the carpetand screwed the pedal stop in the rest of the way. And then took the car for aquick (pun intended) test drive. :-)
Stremsjg 8/22/2010 #104
I always thought that the slow throttle responsiveness onmy 2001 XKR was due to the throttle body being dirty or something. Well today Idecided to make change to my throttle cable. After removing the zip tie Ipopped the square off the bracket turned one turn counterclockwise and insertedthe square back into the bracket and attached a new zip tie. I started the carand took it out for a drive and was amazed at the difference. Gone was theslack in the pedal at very low speed, instead the car was immediately veryresponsive. It definately solved the problem I had with the car since I purchasedit in 2008. Now I am kicking my self for not doing the job sooner. At first Ithought the change had raised the RPM, but after the car was warmed up itsettle down to the normal 600 rpm at idle range. If I can do this job trust meanyone can. You won't be dissappointed.
WhiteXKR 3-18-2011 #189
Don't forget most OBDII readers will report throttle%...any easy way to see what is really going on.
Avos 11-14-2011 #195
What is different to 4.0 cars, is that you can extendedit so that the cable becomes too tight (so to short), and due the pin/lockingmechanism being made in such a way that it allows to slip a nodge when you overtension the cable making it adjust itself. This way you can never over tightenthe cable, and always get a perfect fit.
Avos 5-23-2012 #223
4.0 (AJ26) = only idle and torque reductions (closing thebutterfly) are controlled by the ECU, sortoff semi drive by wire.
4.0 (AJ27) = full drive by wire, but added mechanical limp home function (iircfor only 30% max open at 100% pedal down).
4.2 2003-2006 = full drive by wire, no mechanical link anymore, limp home isalso electronically controlled.
All 3 have a cable attached from the gas pedal to a Pedal positioning sensor,but on the 4.2 it is not attached anymore to the TB so also no mechanical linkanymore.
Cerberus66 5-24-2012 #225 & #226
Basic operation:
1. The accel pedal is the input
2. The engine computer receives this signal and drives the throttle motor(output)
3. The engine computer uses the throttle position sensor as feedback to confirmthe throttle position achieved.
Note:
In the following, "a failsafe" refers to action (such as shutting offpower to the throttle motor or performing fuel cut) taken to ensure safety.
Redundancies on the hardware side:
-Two separate sensor circuits in the accel pedal.
-Two separate circuits to and from the engine computer.
-Separate +5V power supplies and grounds are used for these circuits.
-Two separate sensor circuits in the throttle position sensor.
-Two separate sensor signal circuits to and from the engine computer.
-A pair of springs that close the throttle immediately if power is lost (Thethrottle closer spring is the stronger of the two. The throttle opener springopens the throttle a few degrees to prevent it from freezing closed.)
-Redundant power supplies to the engine computer.
-Multiple CPUs in the engine computer that are making the same calculations,and a watchdog function. (This ensures that the computer doesn't start making'bad decisions'.
-Multiple transistors that must operate in cooperation to power the throttlemotor (no single 'stuck' transistor can cause the throttle motor to open).
Redundancies/failsafes on the control side:
-The input section compares the two signals received from the accelerator pedalsensor. There must always be a fixed voltage relationship between the twosignal wires. If there is an out of spec difference, the MIL illuminates and afailsafe mode begins. (See the following diagram)
-With the separate CPUs/RAM, the watchdog monitors for calculation differencesand if there is a difference, the MIL illuminates and a failsafe mode begins.
-The engine computer controls a set of transistors to operate the throttlemotor. The engine computer monitors voltage and current flow. If either voltageor current is out of spec, or occurs at an improper time, then the MILilluminates and a failsafe mode begins.
-The engine computer monitors the throttle position sensor to confirm theposition of the throttle. If it is not responding correctly, then the MILilluminates and a failsafe mode begins.
-In addition to the types of monitoring mentioned above, the engine computeralso monitors each of the input and output lines for logical inconsistencies,and open and short circuits.
#226
The Throttle By-Wire (TBW) aka Drive-By-Wire (DBW)systems appears to be more complex than they actually are due the theredundancy which is built into the systems for safety reasons. Most TBW systemscontain four major components; (1) the Throttle Actuator Control Relay, (2) theDrive Circuit for the throttle actuator which is located inside the ECU, (3)the Accelerator Pedal Position (APP) assembly, and (4) the Electric ThrottleBody Assembly. With the implementation of the TBW system, manufacturers wereable to eliminate the Idle Air Control (IAC) system because they are able touse the electronic throttle body to control the engine's deceleration and idle.The below diagram will demonstrate the basic TBW system operation, pleasenotice that each sensory component of the TBW system has 6 wires connected toit; we will later explain what each of these wires are for.
The first part of this system is the Throttle Actuator Control Relay whichpowers and protects the TBW circuity. The second part of this system is theAccelerator Pedal Position (APP) assembly which transmits two pedal positioninputs to the ECU. The gas pedal (APP assembly) is effectively two independentpedal position sensors which each contain a +5V reference, a ground reference,and a signal which is sent to the TBW circuitry located inside the ECU. Onesignal is considered the “Main” APP signal and the secondary signal isconsidered the “Sub" APP signal, both of which tell the ECU what thedriver's foot is doing as far as requesting torque from the motor (how much thedriver is pushing down on the gas pedal).
The next part of this system is the Electric Throttle Body Assembly whichconsists of the throttle actuator motor, throttle valve, and 2 throttleposition sensors. Like the APP assembly this part contains 6 wires; two ofwhich are the shared +5V reference and shared ground reference wires whichpower the two TPS sensors, The next two wires are the redundant TPS sensorsignals (Main and Sub) which transmit the position of the throttle blade to theECU. The last two wires are for the throttle actuator control signal, theselines control the opening and closing of the throttle blade.
The last part of this system is the TBW Circuitry located inside the ECU. Thiscircuitry receives the Main and Sub APP signals so it knows what the driver'sfoot is doing (as far as requesting torque) then it sends a square wave, 12volt signal across the two throttle actuator control signal lines to step thethrottle actuator motor with a duty cycle; 100% duty cycle would open thethrottle blade to WOT & 0% duty cycle would keep the throttle blade at thefully closed position. Based on the feedback received from the two TPS sensorsignals located in the Electric Throttle Body Assembly, the TBW system isconstantly receiving inputs (APP & TPS) and controlling outputs (throttleactuator motor) in order to control the throttle blade movement on the vehicle.
What this means to you:
...most modern engines will never show a 0% TPS since the throttle blade isalways kept open (by 2-7%) to start the engine and to maintain idle.
...some modern engines will never report a 100% TPS while at WOT since theirTBW system may have been programmed to only open up to a predetermined point.
...you can be able to change the Rev Limits on an engine by tricking the ECUabout the reported RPM but you may not be able to get the motor to acceleratepast a certain RPM since the throttle body has been programmed to close by apredetermined RPM.
...porting of most modern throttle bodies is not a good idea unless you havethe ability to fully re-calibrate that system.
...most modern engines will not allow the motor to start immediately after thebattery has been disconnected then re-connected or if the ECU has been re-setbecause the systems needs approximately 5 seconds to fully calibrate the TBWsystem. If the battery has been disconnected then re-connected or if the ECUhas been re-set, please allow the key to stay in the ON position for a minimumof 10 seconds to allow the TBW system to calibrate before you try to start theengine.
...providing a constant +12V to the throttle actuator motor will fully open thethrottle blade, providing a constant -12V (reversing the polarity) to thethrottle actuator motor will fully close the throttle blade.
...most modern EMS logic has been calibrated to control the throttle bladeopening and closing speed. We have seen where the throttle blade actually opensslower if you slap down the gas pedal versus gradually depressing the gaspedal.
...most modern EMS programming was established to lessen the emissions outputof the motors, so throttle opening and closing delays have been implemented tolessen the emission output of the motors...not to **** you off.
...most modern vehicles have some sort of Traction Control System which use theElectric Throttle Bodies to control engine torque output.
...most modern vehicles have some artificial throttle response programmed intotheir control. For instance, if the driver is pushing down on the APP 20% the TPSsensor may report a 50% reading. The ECU is creating artificial throttleresponse by opening the throttle valve much more that the driver is requesting.
#227
AVOS help me out here. My 2000 XKR according to yournotes is a AJ27S? or AJ26?
My throttle body butterfly valve is directly connected to my throttle pedal.Can you show me through the JTIS the drive by wire components?
Avos 5-24-2012 #228
You have indeed AJ27 engine, so the throttle is operatedby the ECU, ie drive by wire.
#232
As said, on the AJ27 engines,you have fail safe mode, so the axle is connected to the butterfly so you canoperate it but only for 30% max opening or so (which is pedal to the floor).
You don’t have to take my word for it, so just try it yourself. Have a look atthe butterfly and move the cable to 100% pedal to the floor.
Paul Pavlik 5-25-2012 #239
The Accelerator Cable is connected to a DualPotentiometer Assembly AND a Fail Safe Linkage.
Normally the Potentiometer Signals are used to tell the ECM to open or closethe Throttle Plate. The Fail Safe Linkage does NOT contact the Throttle Platedirectly.
If the Throttle Motor Fails, the Fail Safe Linkage comes into play and DOESConnect to the Throttle Plate Mechanically.
There is a Rotational Lag (in Degrees of Rotation) between the Fail SafeLinkage and the Throttle Plate Shaft Assembly.
This Lag is maintained during normal operation.
In Fail Safe Mode, this Rotational Lag must be taken up before the Fail SafeLinkage contacts the Throttle Plate.
This Lag is subtracted from the Maximum Possible Rotation of the ThrottlePlate, Limiting Throttle opening in Fail Safe Mode.
Red1bw 5-25-12 #240
After resetting Throttle Body Cable I would think onethen would need to reset the following:
Resetting kickdown travel limits
After battery reconnection, the engine management system must ‘re-learn’ thelimits of throttle pedal travel. This is to ensure correct adaptive settingsare stored for kickdown operation. Re-programming is done with the ignitionswitch in position II a follows:
• Slowly press the accelerator pedal fully through the kickdown detent to thefloor. Release the pedal and repeat the action.
Giandanielxk8 5-16-2015 #297
On my car, a 2000 XK8 the adjustment is done as so:
1. Geta friend to mash the throttle and then check for slack.
2. Removescrews circled in red.
3. Spinthe tab that holds the throttle cable around the metal sheath (yellow) untilyou tighten the slack. It's like spinning a bolt on a screw.
4. Retightenthe bolts in red that were removed. You may notice that when tightening thosebolts the throttle cable is tightened just a bit more. Make sure to check againthe throttle position percentage at WOT. It is easy to remove too much slack.