What could cause unresponsive throttle?

[TJM]

clogged fuel filter, clogged air filter, bad spark plugs/wires, low fuel pressure, all of this won't cause the only symptom you are describing.

You clearly have a problem related to the fly-by-wire throttle system. If the throttle plate WAS opening, and the vehicle would not get-up-and-go, you would get a LOT of jerkiness and maybe a stalled engine due to the bad mixture. You didn't mention any jerkiness when the problem occurs.

Instead of hitting everywhere blind, you could get a 150$ OBD2 scanner, that can read real-time data (or even better, a scangauge II), and plug it when you are driving, when the symptoms occurs, look at the ''throttle %'' signal and play with the gas peddle. If nothing happens on the scanner, then it's the throttle plate not opening, then you have your problem pinpointed. Just don't forget that this signal % value is also related to the TPS sensor in your diagnostic.

By your brief description, it is 90% sure that your throttle plate is not opening past idle.

Since the signs point that direction already, let's assume that it is the throttle plate not opening and you have nailed it. What's the fix?

 

[diverscale]

Since the signs point that direction already, let's assume that it is the throttle plate not opening and you have nailed it. What's the fix?

I am not an expert here, just some guy that do his own maintenance and had his share of strange repairs/rebuilds on multiple cars.

But I would start by the easiest. Since the motor seems to open the plate most of the time, The throttle itself, I would not think would be bad, or it would never open. I would firstly look at the device sending the throttle input by your gas peddle, its wires and its connections. Then I would look at the connections/wires at the throttle body. Then look over the same things around the TPS sensor.

As I don't know this fly-by-wire system, I would also try to disconnect the TPS sensor, and start the truck, and see of you can rev-up with it disconnected or not (you will get a check engine and that is normal). IF you can rev-up (pushing the gas peddle) with it disconnected, I would assume the TPS not to be the problem here. If you disconnect the TPS, and the engine do not rev-up, I would strongly suspect the TPS sensor and its component wiring.

This looks like an intermittent electrical problem to me more than a bad throttle body. Electrical problems require patience, and lot of testing with a volt-meter, and I also sometimes use a spare battery, and wires, to connect hot 12volt.

 

[highcj5]

just wondering if you ever got it figured out. I just bought a 99 about 3 months ago and it is kind of doing the same thing. replaced the air filter, cleaned maf, cleaned throttle body, replaced plugs and wires. I am going to replace the fuel filter this weekend. kind of like a gremlin in the runner. lol. it just randomly happens. I have got mine to sputter a little when it is doing it. usually happens when I first take off after starting. if I get mine figured out, I will post up.

 

[TJM]

Well so far I've changed the engine oil, transmission oil, spark plugs and wires. Still happening, and I'm thinking it's probably the TPS. We will be testing that this week to see if it needs to go. After that it'll be the fuel filter, and hopefully I won't have to get to the fuel pump.

The lag seems to come every 4-5 miles of city driving, and always from either a dead stop or a slow roll. Hope to have this resolved soon.

 

[ThorInc]

Well so far I've changed the engine oil, transmission oil, spark plugs and wires. Still happening, and I'm thinking it's probably the TPS. We will be testing that this week to see if it needs to go. After that it'll be the fuel filter, and hopefully I won't have to get to the fuel pump.

The lag seems to come every 4-5 miles of city driving, and always from either a dead stop or a slow roll. Hope to have this resolved soon.

For the price of a TPS sensor, for me it would be a slam dunk.........if you do, get the OEM.

 

[TJM]

For the price of a TPS sensor, for me it would be a slam dunk.........if you do, get the OEM.

That's definitely the plan, hopefully that will resolve the issue. It's my next step. OEM is close to $60 while after market is around $30. I'll go with OEM.

If that doesn't work though, it'll be back to the drawing board.

 

[Morrison]

Any update on the fix? I'm having the same issue now and hooked up realtime monitor of the tps and its jumping from actual position % to idle, then it will jump back without doing anything. It seems to do it more when I'm the vehicle was just starting to go.

 

[prcGTI]

2002_4Runner_SM_pg960.JPG - Google Drive

You didn't say if you were getting any error codes or not, but regardless you can try these TB related inspections with a multi-meter. They may help point you to whether this is a TPS, TB Control Motor, or Accelerator Pedal Position Sensor issue. Also, as others have stated since you have a 2002 you won't be able to just replace the TPS as in a 96-00. The p/n for the 96-00 TPS is 8945235020 whereas the p/n for the TPS on an 01-02 is 8945235030 which is NOT sold separately from the TB. Used TBs for 01-02 run anywhere from $225ish - $400 where new ones are close to $700 (p/n 2203062020).....so that sucks if it turns out to be the TB or TPS.

I have also heard that in some instances the issue turned out to be a short in the in the wiring between the TB/TPS and the ECU... I can't imagine what a pain the butt that would be to #1 diagnose for certain and #2 fix.

Hope some of this helps.

 

[plcfcng]

look back on some older threads there is a replacement part # for 85 bucks he said it worked a 01 or 02. Good luck.:fencing:

 

[mscott9]

Same issue 2016

I am having the same issue with my 2016 4Runner limited. After idling, usually for a few minutes - the engine will remain on but the check engine light will come on and the the throttle will become unresponsive. I have taken to dealer 3 times now. First time they cleaned the throttle, second time they replaced the battery, 3rd visit is in progress. I am just under 36k mileage and am worried I will get another “fix” resulting in same issue. Problem is dangerous as has occurred at stop signs and in traffic while stopped. Any ideas ?

 

[Bad Luck]

I am having the same issue with my 2016 4Runner limited. After idling, usually for a few minutes - the engine will remain on but the check engine light will come on and the the throttle will become unresponsive. I have taken to dealer 3 times now. First time they cleaned the throttle, second time they replaced the battery, 3rd visit is in progress. I am just under 36k mileage and am worried I will get another “fix” resulting in same issue. Problem is dangerous as has occurred at stop signs and in traffic while stopped. Any ideas ?

You would be better off asking this question in the 5th gen 4Runner section. This is the 3rd gen 4Runner section and the our newest vehicle was made in 2002. Good luck!

 

[Skibber]

I had/have this same/similar issue with my 01 and have documented it in another post.
Random hesitation when accelerating

Andy Mod 2.0 (with Trac Switch) pretty much eliminates the issue when active.