Failing throttle position sensor or normal behavior?

[Skulking]

Since I bought my 4runner over a year ago I have had looseness in the gas pedal. There is a part at what should be the beginning of the pedal travel where the pedal just flops around. I assumed it was either the return spring being old, or the throttle cable having a little slack in it. Yesterday I used Torque to check the throttle position during normal driving, and noticed that no matter how floored I had the gas pedal I wasn't seeing the throttle position get past 73.3%. I tightened the throttle cable up some, and nothing changed. This morning I manually actuated the throttle on the engine and holding it fully open I'm still only showing 73.3% for the throttle position. I don't notice any symptoms of a failing throttle position sensor, and I don't have a CEL or any codes. Is this a sign of a throttle position sensor beginning to fail, or is this normal behavior?

Doing research on this subject, it looks like since I have a 2000 4runner (5VZ-FE) the throttle position sensor is easily replaceable unlike on the 01-02 models. I haven't been able to find anything on checking resistance for the sensor to verify function. I appreciate any insight people have on whether this is normal behavior, or any additional things to check before replacing the sensor.

 

[Bad Luck]

Since I bought my 4runner over a year ago I have had looseness in the gas pedal. There is a part at what should be the beginning of the pedal travel where the pedal just flops around. I assumed it was either the return spring being old, or the throttle cable having a little slack in it. Yesterday I used Torque to check the throttle position during normal driving, and noticed that no matter how floored I had the gas pedal I wasn't seeing the throttle position get past 73.3%. I tightened the throttle cable up some, and nothing changed. This morning I manually actuated the throttle on the engine and holding it fully open I'm still only showing 73.3% for the throttle position. I don't notice any symptoms of a failing throttle position sensor, and I don't have a CEL or any codes. Is this a sign of a throttle position sensor beginning to fail, or is this normal behavior?

Doing research on this subject, it looks like since I have a 2000 4runner (5VZ-FE) the throttle position sensor is easily replaceable unlike on the 01-02 models. I haven't been able to find anything on checking resistance for the sensor to verify function. I appreciate any insight people have on whether this is normal behavior, or any additional things to check before replacing the sensor.

Did a full throttle pull today just for you. At 30 mph tps read 72.8% and increases as speed increased. At 75 mph it read 76.2%. I'd say your sensor is accurate and in working condition. If it starts to fail you'll very likely get a dtc for throttle position performance or correlation.

 

[BirdusZippidus]

You'll get a CEL, or a pending code if you're TPS is failing.

First symptom I had recently was the torque converter randomly locking and unlocking. Initially, no stored codes or CEL. After a couple more drives, I had a stored TPS code, but no CEL.

Criteria for the CEL on many codes requires multiple occurrence of the out of range condition.

 

[HiLife]

I did a key on, engine off, floored the gas pedal and I also got 74 of throttle position.
Got a soft code for tps a while back while rough idling for 2 seconds. Cleared the P0120 and both rough idle and tps code never came back.

 

[Skulking]

It seems weird that the sensor doesn't go all the way to 100%, but I guess that is just how it was designed to work. Thank you all for your help.

 

[19963.4lsr5]

It seems weird that the sensor doesn't go all the way to 100%, but I guess that is just how it was designed to work. Thank you all for your help.

Exactly. It’s around 10% at idle and around 75% at WOT.

For the record some jeeps are the same way. If you get a code for the TPS change it. Buy OEM or get one out of a junk yard.


Sent from my iPhone using Tapatalk

 

[brillo_76]

When my failed on my 98 (Tetanus 1) it threw a CEL code. Replaced it with new OEM 2 or 3 years ago and haven't had an issue since..

 

[phattyduck]

It seems weird that the sensor doesn't go all the way to 100%, but I guess that is just how it was designed to work. Thank you all for your help.

Most/all vehicles I have messed with are similar. What matters is that it has continuous and reliable readings, not the absolute min and max value.

-Charlie

 

[Skulking]

Most/all vehicles I have messed with are similar. What matters is that it has continuous and reliable readings, not the absolute min and max value.

-Charlie

That makes sense. I guess that the ECU is probably programmed to see the voltage at 73ish percent as full throttle, and around 10 percent as idle/ closed throttle, and reacts accordingly, but when I'm looking at it with an OBD reader, all I'm actually capturing is the voltage as a percent of full scale for the sensor rather than as a percentage as the ECU reads it.

 

[96RedRunner]

Most encoders and pots, TPS's are set up to not operate at max or min limits.
It creates a buffer zone for catching the signal consistently a plus or minus thing, shows up using a scope.
ECU's, PLC's can be setup to operate with a 0-100% range, looks as Toyota went with standard 10-25 wiggle room.
TPS's I've heard develop a dead spot a hesitation, shortly a code. I have the beginning dead spot, have for a while, waiting.
Been said dead spot could be related to where gas pedal is held at for average operating speeds, miles on TPS.

 

[99sr50809]

Exactly. It’s around 10% at idle and around 75% at WOT.

For the record some jeeps are the same way. If you get a code for the TPS change it. Buy OEM or get one out of a junk yard.


Sent from my iPhone using Tapatalk

Thank you, I’ve been idling at 900 in drive and 1400 in park and nuetural. TPS reads 14% at idle. Throttle body might be getting stuck. If I try to force it the other way it idles down and tps% goes down

 

[Bad Luck]

Thank you, I’ve been idling at 900 in drive and 1400 in park and nuetural. TPS reads 14% at idle. Throttle body might be getting stuck. If I try to force it the other way it idles down and tps% goes down

Is that with your engine cold or at operating temperature?

 

[Riceye]

Thank you, I’ve been idling at 900 in drive and 1400 in park and nuetural. TPS reads 14% at idle. Throttle body might be getting stuck. If I try to force it the other way it idles down and tps% goes down

I'd consider removing the idle air control valve (the part below the throttle body) and clean using an appropriate aerosol, like throttle body cleaner. It's a bit of a pain in the ass, as you have to disconnect the two tiny coolant lines.

The valve has a 'shutter' that opens or closes based on need. If there is any debris present it will likely hang up in the open position, leaving you with a high idle.

I've always removed the throttle body to do this; I'm not even sure you can get to the fasteners if you don't. Being atop the engine, you will only lose a bit of coolant.

Here's a vid from Tim the Toolman. It's 52 min long, and very thorough. Cleaning the IAC starts at about 35 minutes in.

IAC testing and cleaning

Good luck!

 

[Hunter223]

Been having similar symptoms as the OP and even after cleaning and checking the IAC valve and cleaning the throttle body I am seeing the same thing. Did this do the trick for you or did you find it was something else?

 

[T4R2014]

The looseness in the pedal is the rubber bushing rotting and falling off. You'll need a new cable.

 

[espance]

The looseness in the pedal is the rubber bushing rotting and falling off. You'll need a new cable.

Alternatively, if you want a little more life out of your cable or are looking for a quick fix, you can use a piece of rubber hose and some zip ties to replicate the bushing

I found this trick on this forum a while ago, but cannot find the thread. The best I can find is this YouTube video of someone doing the exact same thing I did, but they used a 93 4runner. Mine is a 99 and worked just fine: Link!