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Discussion Starter #1
when i push down on the gas lightly to about 2000 rpm my car starts to drop idle down to about 1200 rpm and bakt to 2000 and over and over again, when i pull this sensor out it wont do it any more but the idle stays at about 1800 rpm... all this happend after i took my throttle body off of it and reinstaled it, do you think the black thing is messed up? what is it? how much? anything else it could be.
here are the pics

 

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that black thing is ur Throttle Postion Sensor (TPS)....

maybe u can try adjusting it by loosening the screws on it and moving it around...
 

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Discussion Starter #3
but that really wont help the idle bounce will it? any one know how much the tps cost new from toyota?
 

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did you take the TPS off when you messed with your throttle body? if so, while you had it off, the shaft could have gotten turned a little bit. when you put it back on, it stayed in the wrong position. so it is telling the computer one thing while your actual throttle position is another.

another possibility is a vacuum leak

still another is your EGR valve. if the EGR is opening a little bit when it isnt supposed to, it can make the RPMs drop unexpectedly.
 

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^^^ take the vacuum line for the EGR valve off the EGR modulator. either hook up a hand held vacuum pump (like the MiteyVac) and give it some vacuum or literally suck on the vacuum line with the engine idling. the engine should run really rough and/or die depending on how much vacuum you give it if it is working properly.
 

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When I had a bouncy idle, I also disconnected the TPS, and my idle changed to a steady 1700-1800rpm. I thought that was the proplem, so I replaced it. Turns out, it wasn't the problem. A new TPS will do the same thing.

It took forever to diagnose my idle bouncing problem with my 5S. It turned out to be the throttle body itself was letting too much air through causing the idle to slowly rise then fall.
 

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Discussion Starter #10
Kpmash01 said:
When I had a bouncy idle, I also disconnected the TPS, and my idle changed to a steady 1700-1800rpm. I thought that was the proplem, so I replaced it. Turns out, it wasn't the problem. A new TPS will do the same thing.

It took forever to diagnose my idle bouncing problem with my 5S. It turned out to be the throttle body itself was letting too much air through causing the idle to slowly rise then fall.
how did you fix it
?

i fooled around with it for about 2 hours, no change, but when i cover any of the two holes inside the throttle body it stops jumping, and more help?
 
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I thought I said it was a ISC valve related problem(ie, the hole in the bottom inside of the throttle body leads to the isc valve),.. mine does the same thing the isc valve doesnt work...... I thought it was the TPS for the longest time...
 

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Discussion Starter #12
shimric said:
I thought I said it was a ISC valve related problem(ie, the hole in the bottom inside of the throttle body leads to the isc valve),.. mine does the same thing the isc valve doesnt work...... I thought it was the TPS for the longest time...
but if i un-plug the tps it goes away.... what is the white conector under the t/b?
 

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Dijital357 said:
^^^ take the vacuum line for the EGR valve off the EGR modulator. either hook up a hand held vacuum pump (like the MiteyVac) and give it some vacuum or literally suck on the vacuum line with the engine idling. the engine should run really rough and/or die depending on how much vacuum you give it if it is working properly.

arright just making sure....b/c what i did was inhooked the vacuum line from the egr itself and connected it to a vacuum line from the intkae manifold....the engine cut off and shut down.
 
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white connector??? errr,...... if it sticks out towards you its the ISC valve im talking about...
 
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tred said:
but if i un-plug the tps it goes away.... what is the white conector under the t/b?
actually, i beleive you have 2 problems,. high idle(ISC valve) then bouncing idle caused by high idle,. that happens whenever rpm's get above 1600 which i believe is the fuel cut off for idle... the ecu cuts fuel so it can drop idle back to w/e your car idles at suspose to be 750-800. or something like that,.. but the ecu is cutting fuel so it drops then goes right back, not sure exactly why it does that. but the bouncing idle isnt a problem, that just happens because the ISC valve isnt keeping idle at 750 like it suspose to,. the tps... that just sences throttle position,. actually i think that is what sends the signal to the ecu to cut fuel because idle got too high..... Check the BGB it will tell you all about the ISC valve and TPS and what they do... I havent read that section in a while. my memory isnt serving me too well...

edit: yea i just looked at the bgb really fast and fuel cut rpm for the 5sfe is 1600, and return is 1500,. so therefore whenever you rpm's get to 1600 fuel cut will happen then it goes back down but since you have high idle caused by the ISC valve which wont let your car drop below 1600 rpm. all the tps does is cut fuel whenever idle gets past 1600. the ISC valve controlls your idle. thats why it stoped cutting fuel and you kept a steady 1500-1700 whenever you disconnected TPS... But if im wrong someone can be more than welcome to correct me because i dont want to lead him in the wrong direction but i think im pretty much right.
 

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tred said:
how did you fix it
?

i fooled around with it for about 2 hours, no change, but when i cover any of the two holes inside the throttle body it stops jumping, and more help?
I went to the junkyard and bought a throttle body off a 1990 Celica and used it. :)
 

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ookk mr. shimric....

soooo, if my idle was 1700, and didnt go down....that would mean fuel cut is not initiating??????

what would cause that??
 
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