I've looked into this problem before I decided to make this post, I noticed there's some conflicting info or just straight up wrong information, but based on what I've read I've gathered what I think is all the relevant information on what I'm experiencing. Here's to hoping that there's a fix that doesn't involve dropping big money on a new throttle body...
First of all, my 4runner is a 2002 Sport Edition and the way the gas pedal interacts with the throttle is different to anything pre-2001. If you don't know, in 01's and 02's, the gas pedal is connected to the throttle body by a mechanical cable. The cable is linked to what Toyota calls the Accelerator Pedal Position Sensor. This sensor talks with the ECM which then talks to the Throttle Control Motor which is what directly actuates the throttle. The pedal position sensor has a certain travel distance where it's just sensing the pedal position, and then at a certain limit will let the pedal actuate the throttle directly, I assume to let you drive home if the sensor itself ever breaks. If I'm understanding the FSM correctly, the Throttle Position Sensor seems to just let the ECM know that it's actuating the throttle correctly. That was pretty long winded but I saw a lot of posts saying that 02's had no throttle cable and other things which are just not true and made trying to diagnose a lot more difficult.
Anyway, the symptoms. While I'm driving, I'll press the gas pedal and there will just be no response at all, no matter how far I press (except for when you push far enough that it actuates the throttle directly). This happens either while moving or from a stop, and will usually start working again after a second of pressing and letting go in a panic. Strangely enough this issue only happens during the summer when it's hot, around over 95 degrees. For some reason it seems like ambient temperature has something to do with it. There's no weird engine behavior while it's happening and there's no check engine light or any stored codes whatsoever. Cruise control might also be affected but I've only experienced it a couple times, as opposed to dozens while driving normally. I've also never been able to reproduce it when sitting in park or neutral, but to be fair I haven't really tried that much. I can pretty reliably get it to happen on purpose while driving by pressing the gas pedal repeatedly until it happens. I think it's been having this issue for as long as I've been driving it, since 2021. Before that it was my dad's daily driver, and he mentioned that this issue has happened to him before. So this has been happening since at least 2018. It also seems like it's been happening more frequent every year, once summer starts and it's hot outside. Just today over 30 minutes it must have happened at least 20 times.
The first test I did was to get into Torque Pro and graph the TPS values over time. Predictably it showed that as I was experiencing the issue the value of the TPS was not changing. Then I looked in the FSM to diagnose each sensor. The only thing that stood out from this was that the throttle control motor clutch resistance was 5.5 ohms, 0.3 over what Toyota considers to be the max range (4.2 - 5.2). But their listed range is for a temperature of 68 degrees and it was over 100 when I measured. Unfortunately Torque Pro can't read the values from the pedal position sensor which is what I would do next. The FSM shows you can do it manually by testing the voltage on a couple pins on the ECM, but for something intermittent like this it seems unreasonable to hold my voltmeter test probes down there while I have a friend drive around for 30 minutes. Not that it would matter in the end since if any of the sensors where actually broken you have to replace the entire throttle body!
That's where it stands currently. Honestly after writing such an essay of a post I feel like I need to just accept that a new throttle body is the only way out! In any case, any help is appreciated.
First of all, my 4runner is a 2002 Sport Edition and the way the gas pedal interacts with the throttle is different to anything pre-2001. If you don't know, in 01's and 02's, the gas pedal is connected to the throttle body by a mechanical cable. The cable is linked to what Toyota calls the Accelerator Pedal Position Sensor. This sensor talks with the ECM which then talks to the Throttle Control Motor which is what directly actuates the throttle. The pedal position sensor has a certain travel distance where it's just sensing the pedal position, and then at a certain limit will let the pedal actuate the throttle directly, I assume to let you drive home if the sensor itself ever breaks. If I'm understanding the FSM correctly, the Throttle Position Sensor seems to just let the ECM know that it's actuating the throttle correctly. That was pretty long winded but I saw a lot of posts saying that 02's had no throttle cable and other things which are just not true and made trying to diagnose a lot more difficult.
Anyway, the symptoms. While I'm driving, I'll press the gas pedal and there will just be no response at all, no matter how far I press (except for when you push far enough that it actuates the throttle directly). This happens either while moving or from a stop, and will usually start working again after a second of pressing and letting go in a panic. Strangely enough this issue only happens during the summer when it's hot, around over 95 degrees. For some reason it seems like ambient temperature has something to do with it. There's no weird engine behavior while it's happening and there's no check engine light or any stored codes whatsoever. Cruise control might also be affected but I've only experienced it a couple times, as opposed to dozens while driving normally. I've also never been able to reproduce it when sitting in park or neutral, but to be fair I haven't really tried that much. I can pretty reliably get it to happen on purpose while driving by pressing the gas pedal repeatedly until it happens. I think it's been having this issue for as long as I've been driving it, since 2021. Before that it was my dad's daily driver, and he mentioned that this issue has happened to him before. So this has been happening since at least 2018. It also seems like it's been happening more frequent every year, once summer starts and it's hot outside. Just today over 30 minutes it must have happened at least 20 times.
The first test I did was to get into Torque Pro and graph the TPS values over time. Predictably it showed that as I was experiencing the issue the value of the TPS was not changing. Then I looked in the FSM to diagnose each sensor. The only thing that stood out from this was that the throttle control motor clutch resistance was 5.5 ohms, 0.3 over what Toyota considers to be the max range (4.2 - 5.2). But their listed range is for a temperature of 68 degrees and it was over 100 when I measured. Unfortunately Torque Pro can't read the values from the pedal position sensor which is what I would do next. The FSM shows you can do it manually by testing the voltage on a couple pins on the ECM, but for something intermittent like this it seems unreasonable to hold my voltmeter test probes down there while I have a friend drive around for 30 minutes. Not that it would matter in the end since if any of the sensors where actually broken you have to replace the entire throttle body!
That's where it stands currently. Honestly after writing such an essay of a post I feel like I need to just accept that a new throttle body is the only way out! In any case, any help is appreciated.
