TPS Throttle Stop Screw Location w picture
06-20-13, 12:58 PM
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TPS Throttle Stop Screw Location w picture
Afternoon, I'm having a time of it attempting to adjust my TPS. I have all the tools to adjust it. Just making sure that this is the Throttle Stop Screw. Please confirm.
Thanks in advance. I'm sorry I may have further questions if I'm not successful.
Thanks in advance. I'm sorry I may have further questions if I'm not successful.
06-20-13, 10:02 PM
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Wait, what is circled in the pic is actually called the iss, idle stop screw which controls the idle rpm. The actual tps is called throttle position sensor. My car had an issue where it would accel by itself or it would die randomly. Had to mess around with both in order to fix my issue.
06-21-13, 07:22 AM
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Wait, what is circled in the pic is actually called the iss, idle stop screw which controls the idle rpm. The actual tps is called throttle position sensor. My car had an issue where it would accel by itself or it would die randomly. Had to mess around with both in order to fix my issue.
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06-21-13, 01:58 PM
#8
typically you do not want to adjust the idle stop set screw. if you are you finding yourself needing to turn that and you have made no serious changes to your engine, you are most likely covering up the real problem.
most idle issues will be related to adjusting the tps, the black plastic thing on the side with 2 screws.
the idle stop set screw does not need to be moved from where it was set at the factory, unless the idle air valve is completely out of range which doesn't really happen unless they get gunked up or fail, and your idle would be really low. again not a problem with where the screw is set at all.
not sure why you are trying to touch the screw or why you think you have a tps problem but if you keep messing with the throttle body it won't help you will just end up trying to figure out where it was originally set later on and have to play with it a bunch.
most idle issues will be related to adjusting the tps, the black plastic thing on the side with 2 screws.
the idle stop set screw does not need to be moved from where it was set at the factory, unless the idle air valve is completely out of range which doesn't really happen unless they get gunked up or fail, and your idle would be really low. again not a problem with where the screw is set at all.
not sure why you are trying to touch the screw or why you think you have a tps problem but if you keep messing with the throttle body it won't help you will just end up trying to figure out where it was originally set later on and have to play with it a bunch.
06-25-13, 06:42 AM
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typically you do not want to adjust the idle stop set screw. if you are you finding yourself needing to turn that and you have made no serious changes to your engine, you are most likely covering up the real problem.
most idle issues will be related to adjusting the tps, the black plastic thing on the side with 2 screws.
the idle stop set screw does not need to be moved from where it was set at the factory, unless the idle air valve is completely out of range which doesn't really happen unless they get gunked up or fail, and your idle would be really low. again not a problem with where the screw is set at all.
not sure why you are trying to touch the screw or why you think you have a tps problem but if you keep messing with the throttle body it won't help you will just end up trying to figure out where it was originally set later on and have to play with it a bunch.
most idle issues will be related to adjusting the tps, the black plastic thing on the side with 2 screws.
the idle stop set screw does not need to be moved from where it was set at the factory, unless the idle air valve is completely out of range which doesn't really happen unless they get gunked up or fail, and your idle would be really low. again not a problem with where the screw is set at all.
not sure why you are trying to touch the screw or why you think you have a tps problem but if you keep messing with the throttle body it won't help you will just end up trying to figure out where it was originally set later on and have to play with it a bunch.
06-25-13, 10:07 AM
#10
what are the symptoms you are having now? and what were they before you changed the tps?
Since its idling wrong since you replaced the tps, that confirms it for me that it is just the tps.
First thing I would do is throw the multimeter out the closest window, and adjust the tps by feel.
rotating just the tps alone, believe it or not, will raise or lower your idle depending on the direction you turn it.
you can go by the book, but in my experience thats not always where the engine is happiest.
if your idle is too low, when facing your tps turn it counter clockwise (sc300). it should increase your idle and then you will hit a point about half way through the adjustment range where the car will want to stall out or stumble. at this point you back it off (clockwise) just until it stops doing that. this will give you the max possible rpm's with the idl circuit still operating correctly, and the idle valve then can take care of the rest. edit* I may have gotten the clockwise and counter clockwise backwards but play around with it.
basically, mark your original position and play with the tps, and when you think you have a good spot rev the throttle body by hand to see how it revs and how smoothly it comes back. there is only a small range where it will work fine and idle normally. If I had to guess I would say your tps is probably turned mostly clockwise right now on the adjustment range. if none of that adjustments are working or changing how the motor is running or reacts, then unplug the tps and see if there is a change. if there is no change then you may have a shorted tps on your hands which is possible to have without a check engine light.
Since its idling wrong since you replaced the tps, that confirms it for me that it is just the tps.
First thing I would do is throw the multimeter out the closest window, and adjust the tps by feel.
rotating just the tps alone, believe it or not, will raise or lower your idle depending on the direction you turn it.
you can go by the book, but in my experience thats not always where the engine is happiest.
if your idle is too low, when facing your tps turn it counter clockwise (sc300). it should increase your idle and then you will hit a point about half way through the adjustment range where the car will want to stall out or stumble. at this point you back it off (clockwise) just until it stops doing that. this will give you the max possible rpm's with the idl circuit still operating correctly, and the idle valve then can take care of the rest. edit* I may have gotten the clockwise and counter clockwise backwards but play around with it.
basically, mark your original position and play with the tps, and when you think you have a good spot rev the throttle body by hand to see how it revs and how smoothly it comes back. there is only a small range where it will work fine and idle normally. If I had to guess I would say your tps is probably turned mostly clockwise right now on the adjustment range. if none of that adjustments are working or changing how the motor is running or reacts, then unplug the tps and see if there is a change. if there is no change then you may have a shorted tps on your hands which is possible to have without a check engine light.
Last edited by Ali SC3; 06-30-14 at 11:16 AM.
06-28-14, 05:04 PM
#11
I'm on an old thread bump today, but at least this one is only a year old. 
Ali, as you may recall from a recent thread, I adjusted my throttle stop screw as part of my TPS adjustments (using the multimeter and feeler gauges) to eliminate the partial throttle hesitation/bucking around 40 mph. And shortly after that, the car developed start-stall issues and then the bucking came back.
So, searching for how to properly set the throttle stop screw, I came across this thread and another one with a similar message:
"DO NOT MESS WITH THE STOP SCREW BEHIND THE THROTTLE LEVER. THis is NOT intended to be messed with and once moves is impossible to get back right."
http://www.justanswer.com/lexus/3jmo...ne-starts.html
Ruh-roh. Actually, all may not be lost... I remembered roughly where it was to begin with, and the FSM (FI-73) hints at a pretty simple method of setting it:
"Check that there is no clearance between the throttle stop screw and throttle lever when the throttle valve is fully closed."
Fortunately, the spot where a closed throttle valve coincided with no gap between the screw and lever was right about where I expected it should be. So, I tightened it down there and followed your suggestion to set the TPS by hand; also echoed by Lexls' "unofficial" method:
http://www.lexls.com/tutorials/EFI/tps.html
I had to go all the way counter-clockwise to find a spot the TPS is happy with, surprisingly. And that just barely gives me enough idle (right around 500 rpm). But, with a cracked IACV housing and dead MAF, there could well be other factors at play there. Hopefully, getting those replaced will allow it to find the sweet spot a bit better. I think my prior adjustment of the throttle stop screw (in an attempt to both raise the idle and find a spot where the TPS adjustments could meet the continuity specs), per the method detailed in another thread, had simply disguised the fact that the TPS didn't have enough range due to stuff outside its control.
It's starting right up now and running smooth. If it stays this way for more than 24 hours, I'll be quite pleased.
I'm now a believer in setting the TPS by hand! Doing so with the multimeter was so sensitive, just putting pressure on the TPS while tightening it down was enough to change continuity in and out of spec, let alone actually rotating it.
BTW, are we sure "throttle stop screw" and "idle stop screw" aren't two terms for the same thing, like "idle air control" (IAC) and "idle speed control" (ISC)? The OP's picture sure looks like what the FSM shows as the throttle stop screw.
Ali, as you may recall from a recent thread, I adjusted my throttle stop screw as part of my TPS adjustments (using the multimeter and feeler gauges) to eliminate the partial throttle hesitation/bucking around 40 mph. And shortly after that, the car developed start-stall issues and then the bucking came back.
So, searching for how to properly set the throttle stop screw, I came across this thread and another one with a similar message:
"DO NOT MESS WITH THE STOP SCREW BEHIND THE THROTTLE LEVER. THis is NOT intended to be messed with and once moves is impossible to get back right."
http://www.justanswer.com/lexus/3jmo...ne-starts.html
Ruh-roh. Actually, all may not be lost... I remembered roughly where it was to begin with, and the FSM (FI-73) hints at a pretty simple method of setting it:
"Check that there is no clearance between the throttle stop screw and throttle lever when the throttle valve is fully closed."
Fortunately, the spot where a closed throttle valve coincided with no gap between the screw and lever was right about where I expected it should be. So, I tightened it down there and followed your suggestion to set the TPS by hand; also echoed by Lexls' "unofficial" method:
http://www.lexls.com/tutorials/EFI/tps.html
I had to go all the way counter-clockwise to find a spot the TPS is happy with, surprisingly. And that just barely gives me enough idle (right around 500 rpm). But, with a cracked IACV housing and dead MAF, there could well be other factors at play there. Hopefully, getting those replaced will allow it to find the sweet spot a bit better. I think my prior adjustment of the throttle stop screw (in an attempt to both raise the idle and find a spot where the TPS adjustments could meet the continuity specs), per the method detailed in another thread, had simply disguised the fact that the TPS didn't have enough range due to stuff outside its control.
It's starting right up now and running smooth. If it stays this way for more than 24 hours, I'll be quite pleased.
I'm now a believer in setting the TPS by hand! Doing so with the multimeter was so sensitive, just putting pressure on the TPS while tightening it down was enough to change continuity in and out of spec, let alone actually rotating it.
BTW, are we sure "throttle stop screw" and "idle stop screw" aren't two terms for the same thing, like "idle air control" (IAC) and "idle speed control" (ISC)? The OP's picture sure looks like what the FSM shows as the throttle stop screw.
06-30-14, 11:21 AM
#12
Yeah I think I was backwards on the clockwise and the counter clockwise, but I think you got it right when on the right side the motor will want to idle down and that sort of lets you know the IACV is working, and it will want to go to 500-600 rpm's with the a/c off, and that just means you've got everything running well because that is how they are factory you can hardly tell the thing is on till you step on it.
Pretty sure those 2 names are for the same thing the screw is a throttle stop screw, but on older cars that is how you set the idle. on newer Toyota's there is a base position set on the screw at the factory, and then the IACV does the rest, but it still works like before as in you could raise the idle that way, its just not a good idea as it affects other stuff on these newer cars.
if you raise it too much the tps will never sit in the closed position because you can only turn it a certain amount counter clockwise before its going to always read a few degrees open. Also it messes with the EGR system and EVAP system, as those are connected to ports on the top of the throttle body that work by the throttle blade passing it, but if you open the throttle too much via screw, those will not be working right also.
If you make an adjustment small enough to not affect those, usually the idle valve will just adjust back so yeah there is no good way to adjust the idle on these cars, unless you have all that stuff removed then feel free to riase it up to whatever, like I used to with my q45 throttle body and FFIM I would have it idling at 1200 rpm's via the screw just so I could get better cold starts.
Generally you wont be doing this stuff though if you want it to be like stock, unless someone has done it before you incorrectly. look for the factory paint mark on the screw and see if it lines up.
Pretty sure those 2 names are for the same thing the screw is a throttle stop screw, but on older cars that is how you set the idle. on newer Toyota's there is a base position set on the screw at the factory, and then the IACV does the rest, but it still works like before as in you could raise the idle that way, its just not a good idea as it affects other stuff on these newer cars.
if you raise it too much the tps will never sit in the closed position because you can only turn it a certain amount counter clockwise before its going to always read a few degrees open. Also it messes with the EGR system and EVAP system, as those are connected to ports on the top of the throttle body that work by the throttle blade passing it, but if you open the throttle too much via screw, those will not be working right also.
If you make an adjustment small enough to not affect those, usually the idle valve will just adjust back so yeah there is no good way to adjust the idle on these cars, unless you have all that stuff removed then feel free to riase it up to whatever, like I used to with my q45 throttle body and FFIM I would have it idling at 1200 rpm's via the screw just so I could get better cold starts.
Generally you wont be doing this stuff though if you want it to be like stock, unless someone has done it before you incorrectly. look for the factory paint mark on the screw and see if it lines up.
Last edited by Ali SC3; 06-30-14 at 11:26 AM.
06-30-14, 04:05 PM
#13
I don't think my stop screw had a factory paint mark, unless that's what the orange stuff was that looked like thread lock? If that was a paint mark, then someone had adjusted the stop screw previously by moving the nut down over the mark. I scraped it all off when doing the first adjustment, so I don't have that mark to go back to...
Any idea what would cause a sucking sensation when letting off the throttle at 60 mph? It feels like the throttle plate is being sucked closed when straddling that fine line between light throttle and coasting. I'm guessing I still don't have the stop screw set quite right, but the IAC/MAF issues could be to blame. Also, I played with the Dashpot a bit (didn't end up changing anything) prior to that, and its purpose sort of seems like it could come into play there, by letting the throttle plate to close too quickly.
Any idea what would cause a sucking sensation when letting off the throttle at 60 mph? It feels like the throttle plate is being sucked closed when straddling that fine line between light throttle and coasting. I'm guessing I still don't have the stop screw set quite right, but the IAC/MAF issues could be to blame. Also, I played with the Dashpot a bit (didn't end up changing anything) prior to that, and its purpose sort of seems like it could come into play there, by letting the throttle plate to close too quickly.
07-02-14, 09:52 AM
#14
no idea what you are talking about with the sucking sensation. if you have your foot even slightly on the throttle none of the screws are going to help you. you really adjust those at idle when motor is warmed out and it should be 95% backed out the screw. you kind of turn it all the way out and then turn it in till you feel some resistance, thats when it actually moves the plate. right there where you hit the resistance is about the right place to lock it down, maybe a hair past.
the dashpot keeps the throttle plate open for a sec on rapid deceleration to allow extra air in to keep from backfiring and getting a clean burn for emissions.
the dashpot keeps the throttle plate open for a sec on rapid deceleration to allow extra air in to keep from backfiring and getting a clean burn for emissions.