Temporary, intermittent loss of power/hesitation

2002, SR5, 4WD, 170,000 miles

While driving, or starting from a stop, my 4Runner will lose power. It’s as if I took my foot off the accelerator. The engine doesn't die, it's just that the RPMs drop to idle and there is no response to the accelerator pedal. It doesn’t matter if move the pedal, floor it or do anything else. The power just cuts out. Within 1 to 3 seconds, it will regain power. However – and I think this is interesting – the power doesn’t come back with the power equivalent to the pedal position. It always ramps up slowly as if I’m starting slowly from a stop. In other words, if I have the pedal floored, when the power returns, it doesn’t jump to full throttle. It slowly builds back up to whatever position I have the pedal in.

The problem comes and goes. It will last for a few days, then be gone for weeks.

If it was the throttle position sensor, would the throttle slowly build up like it does or would it suddenly return to whatever position the pedal is in? Could it be the ECM?

I originally had a long crank issue that turned out to be a vacuum leak, but in the process, I did A LOT of work. All of this has been done

- Checked and cleaned all grounds in the engine compartment
- Replaced plugs
- Replaced plug wires
- Replaced battery
- Replaced fuel filter
- Replaced air filter
- Replaced PCV valve
- Replaced fuel pump and pump screen
- Replaced front (AF) and rear O2 sensors
- Replaced Fuel Pressure Regulator
- Refurbished original OEM fuel injectors
- Cleaned MAF sensor
- Cleaned throttle body
- Disconnected battery to clear memory
- Smoke tested for vacuum leaks – replaced hose clamps and vacuum plugs
- Ohm tested Throttle Control Motor, Throttle Position Sensor and Accelerator Pedal Position Sensor – all 3 passed (the 2002 doesn’t have an Idle Air Control Valve)
- No check engine light and no stored codes
- Ran through 2 cans of seafoam
- Replaced every fuse related to the ECU or fuel injection
- Took it to mechanic twice and he couldn't find anything

geez that's sounding a lot like a clutch problem i had with my pickup, but it's a manual and i see you've got a 2002 so that cause won't port over exactly. does your auto have a speed sensor on the transmission, and it could possibly be fouled? sorry for not being very familiar with that transmission. is this among those you resistance-tested? there's one on the tcase too?

This sounds like when my overactive VSC/TRAC system kicks on. Do you ever notice the VSC/TRAC lights coming in during this?

You could test your wheel speed sensors, check the for damage/gear oil on them, and make sure they're proper seated (not lifting up from rust). You could also try disabling the VSC/TRAC system to see if still happens to rule this. I don't know how to do it, but the Andy Mod deals with this that.

Have you looked at live data of your throttle position sensor while slowly applying the throttle? There might be a dead spot in the sensor that you won't pick up with a resistance check.

What is your Fuel Trims ST/LT, and what is the MAF temp and flow readings. I'd probably throw a new MAF at it if you can't pull live data.

I would look into a clogged cat a Vac gauge that reads low is a easy check.. :clock:

I haven't had the problem for three months, but it came back today. It was worse than any previous events - the vehicle lost power, but this time it didn't come back and had to pull over to side of the road. The good news is, I finally got a trouble code:

P1126
Raw code: 1126
ECU: 10
Status: Confirmed
OBDII: Throttle Position (Narrow Range) Sensor Circuit Malfunction
Toyota: Magnetic Clutch Circuit Malfunction

Any recommendations on diagnostics?
I've read the TPS on my 2002 is not replaceable and the entire throttle body would need to be replaced. Any thoughts on that?

Based on post #25 in this thread, looks like replacing the throttle body is the way to go.

Throttle Position Sensor.....?

I installed a new throttle body today. If there are any issues I’ll be sure to post. No news is good news.

A note about replacing the TB: when I first started the engine, there was no throttle response for about half the travel of the accelerator pedal. I let the engine run for about 20 minutes and by then I suppose the computer figured out what had just happened and then there were no issues. I also replaced the TB gasket and torqued the two bolts and two nuts to factory specs since vacuum leaks had been giving me fits. Wanted to make sure I’d have no more of those.

gruenegenes said:

I installed a new throttle body today. If there are any issues I’ll be sure to post. No news is good news.

A note about replacing the TB: when I first started the engine, there was no throttle response for about half the travel of the accelerator pedal. I let the engine run for about 20 minutes and by then I suppose the computer figured out what had just happened and then there were no issues. I also replaced the TB gasket and torqued the two bolts and two nuts to factory specs since vacuum leaks had been giving me fits. Wanted to make sure I’d have no more of those.

Click to expand...

Sorry you had to buy a new one. I used to sell used throttle bodies off 01-02's as the new price is quite expensive for a Toyota part. I think this should solve your issues. I also had phantom issues which the TPS was to blame, it will start to fail but not bad enough to throw a code and cause all sort of havoc.

mine has been doing the same thing for years, usually just when its hot out. this year has been especially bad though.I usually just tolerate it.

so the conses is replace the whole throttle body assembly?

jinxed13 said:

mine has been doing the same thing for years, usually just when its hot out. this year has been especially bad though.I usually just tolerate it.

so the conses is replace the whole throttle body assembly?

Click to expand...

It’s my understanding that for the 01 and 02, the Throttle Position Sensor cannot be replaced separately from the throttle body. I’ve read of some folks who have done it, but you have to find a 4 pin TPS and then calibrate it with another sensor on the TB, but many advised against it. Good luck! Such a frustrating problem.

update for anyone following. i replaced the tps with the 4 pin sensor from parts geek. it idled high for a few starts and then learned the new part. no more surging or hesitation.

The car is running fine, but it threw this code yesterday

P1126
Raw code: 1126
ECU: 10
Status: Confirmed
OBDII: Throttle Position (Narrow Range) Sensor Circuit Malfunction
Toyota: Magnetic Clutch Circuit Malfunction

I think the only things left to replace are the ECU and coolant temp sensor. Aside from those, I suppose it could be a short somewhere.

Any Updates? Same Problem on my 2001 SR5

Hey!

Any updates on your issue/ fix after this long?

I just began having the same exact issue about two weeks ago, where I found myself stranded on the side of the road at an idle with no throttle response. The VSC , TRAC, and CEL all turned on at the moment I lost throttle. I cycled the ignition once by shutting off and starting the car, and it seemed to fix the problem. After getting home and doing a few test drives, the same throttle cut-out issue was happening under acceleration and load.

After some quick searching I decided to order a new 4 prong TPS from Aisan part#(89452-35030). This is the cheapest way around changing the TPS without changing the whole Throttle Body on a 2001-2002.

All of my check engine lights went off, and the issue seemed to be fixed for about a week, until it came back this evening on the drive home.

My only other idea for this very specific issue is a throttle body replacement, possibly a used one off of a junked 2001 SR5.

I am getting a P1120 code which my Blue Driver says: Throttle/Pedal Position Sensor/ Coolant Flow control ValvePosition Sensor Circuit
Does this mean I should look at the PPS now? Not sure If I could even get one of those

Any updates at all since doing it in 2021 would be GREATLY appreciated!

thanks!!

logan

I am getting a P1120 code which my Blue Driver says:

Throttle/Pedal Position Sensor/ Coolant Flow control ValvePosition Sensor Circuit

Does this mean I should look at the PPS now? Not sure If I could even get one of those.

4runner970 said:

Hey!

Any updates on your issue/ fix after this long?

I just began having the same exact issue about two weeks ago, where I found myself stranded on the side of the road at an idle with no throttle response. The VSC , TRAC, and CEL all turned on at the moment I lost throttle. I cycled the ignition once by shutting off and starting the car, and it seemed to fix the problem. After getting home and doing a few test drives, the same throttle cut-out issue was happening under acceleration and load.

After some quick searching I decided to order a new 4 prong TPS from Aisan part#(89452-35030). This is the cheapest way around changing the TPS without changing the whole Throttle Body on a 2001-2002.

All of my check engine lights went off, and the issue seemed to be fixed for about a week, until it came back this evening on the drive home.

My only other idea for this very specific issue is a throttle body replacement, possibly a used one off of a junked 2001 SR5.

I am getting a P1120 code which my Blue Driver says: Throttle/Pedal Position Sensor/ Coolant Flow control ValvePosition Sensor Circuit
Does this mean I should look at the PPS now? Not sure If I could even get one of those

Any updates at all since doing it in 2021 would be GREATLY appreciated!

thanks!!

logan

Click to expand...

Sorry to hear you’re having this problem! After replacing the throttle body, the power loss never returned. I had a code about a month later (but no power loss) and that was it. I haven’t had any issues since and it’s been about 14 months.

The power loss is back along with code P1126. If anybody has made progress on this please let me know. I’m going to take it to a shop to try to diagnose.

In for the updates....my 2002 has shown similar symptoms over the past year, but the power always comes back within a second or two.

This is interesting:
https://www.youtube.com/watch?v=KT0TTDeCFzw&feature=youtu.be

https://www.youtube.com/watch?v=9wlvYaMNivs&feature=youtu.be

I’m not sure I want to do that much disassembly to see if this is my problem, but I’m kind of out of ideas.