Sudden Acceleration! Prius Problem with 08 LR3!
#21
10-26-2018, 08:21 AM
One year later no acceleration issues replaced both
So nearly a year after replacing both the throttle body and accelerator pedal, I have not had any unexpected acceleration events. absolutely none.
in my non statistically significant sample set of one replacing both seems to have solved the problem. I did acquire both parts used providing a small risk that the parts I received would also have the problem but the price of both parts used was significantly lower, and both parts seem to be readily available in the surplus & salvage market.
for the record replacing both worked in my case
KC0PAH - .... .- -. -.- ...
in my non statistically significant sample set of one replacing both seems to have solved the problem. I did acquire both parts used providing a small risk that the parts I received would also have the problem but the price of both parts used was significantly lower, and both parts seem to be readily available in the surplus & salvage market.
for the record replacing both worked in my case
KC0PAH - .... .- -. -.- ...
This problem has not happened to me in reverse only at idle or moving forward when slowing usually at or just before a stop. Like someone said, always prepared to throw it in neutral or park. Be advised that it then revs to redline bouncing the rev limiter too. So be prepared to turn the key too. After about 30 seconds the truck starts and drives normally (at least for another 6 months or so)
I have replaced both the gas pedal with sensor and throttle body and its sensor. Since the problem only takes place about once every 6 months I will report back if it happens after the parts change. in that case the ECU for $1500 (used) would be next other than random wiring faults. I hate trowing parts at a problem.
It would be good for others researching this problem to post so we have some idea how rare this problem is.
thanks
KC0PAH
I have replaced both the gas pedal with sensor and throttle body and its sensor. Since the problem only takes place about once every 6 months I will report back if it happens after the parts change. in that case the ECU for $1500 (used) would be next other than random wiring faults. I hate trowing parts at a problem.
It would be good for others researching this problem to post so we have some idea how rare this problem is.
thanks
KC0PAH
#22
05-16-2019, 04:04 PM
This problem has not happened to me in reverse only at idle or moving forward when slowing usually at or just before a stop. Like someone said, always prepared to throw it in neutral or park. Be advised that it then revs to redline bouncing the rev limiter too. So be prepared to turn the key too. After about 30 seconds the truck starts and drives normally (at least for another 6 months or so)
I have replaced both the gas pedal with sensor and throttle body and its sensor. Since the problem only takes place about once every 6 months I will report back if it happens after the parts change. in that case the ECU for $1500 (used) would be next other than random wiring faults. I hate trowing parts at a problem.
It would be good for others researching this problem to post so we have some idea how rare this problem is.
thanks
KC0PAH
I have replaced both the gas pedal with sensor and throttle body and its sensor. Since the problem only takes place about once every 6 months I will report back if it happens after the parts change. in that case the ECU for $1500 (used) would be next other than random wiring faults. I hate trowing parts at a problem.
It would be good for others researching this problem to post so we have some idea how rare this problem is.
thanks
KC0PAH
#23
11-29-2019, 01:12 PM
I own a 2006 LR3 V8 and have experienced unexplained acceleration 3 times.
It is pretty obvious when it happens. It is an unmistakable feeling to have to nearly stand on the brake while the truck revs to 5000 rpm. You slam it into park and it revs to 7000 rpm and bounces the rev limiter. Turning off the key is the obvious reaction but know if in motion this kills the power steering and might engage steering wheel ignition lock, a bad thing if still in motion. I have always been at a standstill, not moving when the runaway takes place.
The first time it happened to me waiting in a line to drop off recycled goods, literally idling in the line with my foot lightly on the brake. The truck accelerated higher and higher as I applied increasing pressure to the brake. To those who ask stupid questions "like are you sure you were pressing the right pedal"? I am sure!, I am a mechanic. I had plenty of time to react. Enough to verify that no floor mats were on the accelerator and my foot was not crossways on the throttle either. While in park letting it rev to near red-line for 20 seconds(ouch) I can confirm that the gas pedal was free to be depressed and return freely, it was not encumbered in any way.
The second occurrence I was parking in my daughter's driveway and experienced throttle runaway, she was in her car having just followed her home, She asked me why I revved the truck to red-line before shutting it off. I had the presence of mind the second time to look at the gas pedal position sensor and pedal nothing wrong there. Popped the hood inspected throttle body contacts and tapped around MAF for shorts and such. Getting back in the truck and restarting the engine it went immediately to red-line in neutral, and I shut it off. I tried reseating the connector above the gas pedal as well as the MAF sensor and on the air intake and connector throttle body. 90 seconds later the truck started and ran normally for another 6 months.
The third happenstance of throttle runaway, I simply stopped at a traffic light. Sitting at idle with my foot at medium pressure on the brake. The truck starts increasing RPMs and climbing forward. I depress the brake harder and it continues to climb up to about 5000 to 5200 RPM. I turn off the ignition. I restart the truck and all is fine for my drive home.
You are not alone in experiencing throttle runaway on an LR3. I just wanted to document this here for others that seem to be searching for details.
It is problematic to diagnose something that happens once every 6 months to a year and works so gloriously well the rest of the time.
kc0pah
It is pretty obvious when it happens. It is an unmistakable feeling to have to nearly stand on the brake while the truck revs to 5000 rpm. You slam it into park and it revs to 7000 rpm and bounces the rev limiter. Turning off the key is the obvious reaction but know if in motion this kills the power steering and might engage steering wheel ignition lock, a bad thing if still in motion. I have always been at a standstill, not moving when the runaway takes place.
The first time it happened to me waiting in a line to drop off recycled goods, literally idling in the line with my foot lightly on the brake. The truck accelerated higher and higher as I applied increasing pressure to the brake. To those who ask stupid questions "like are you sure you were pressing the right pedal"? I am sure!, I am a mechanic. I had plenty of time to react. Enough to verify that no floor mats were on the accelerator and my foot was not crossways on the throttle either. While in park letting it rev to near red-line for 20 seconds(ouch) I can confirm that the gas pedal was free to be depressed and return freely, it was not encumbered in any way.
The second occurrence I was parking in my daughter's driveway and experienced throttle runaway, she was in her car having just followed her home, She asked me why I revved the truck to red-line before shutting it off. I had the presence of mind the second time to look at the gas pedal position sensor and pedal nothing wrong there. Popped the hood inspected throttle body contacts and tapped around MAF for shorts and such. Getting back in the truck and restarting the engine it went immediately to red-line in neutral, and I shut it off. I tried reseating the connector above the gas pedal as well as the MAF sensor and on the air intake and connector throttle body. 90 seconds later the truck started and ran normally for another 6 months.
The third happenstance of throttle runaway, I simply stopped at a traffic light. Sitting at idle with my foot at medium pressure on the brake. The truck starts increasing RPMs and climbing forward. I depress the brake harder and it continues to climb up to about 5000 to 5200 RPM. I turn off the ignition. I restart the truck and all is fine for my drive home.
You are not alone in experiencing throttle runaway on an LR3. I just wanted to document this here for others that seem to be searching for details.
It is problematic to diagnose something that happens once every 6 months to a year and works so gloriously well the rest of the time.
kc0pah
Last edited by enb54; 11-29-2019 at 01:13 PM. Reason: 2nd time
#24
11-29-2019, 09:32 PM
Rock Crawling
#25
11-29-2019, 11:14 PM
I don't really know, I think only petrol (gasoline) engines but I am going to try and spend some time with an oscilloscope and +5VDC power supply to try and see what is happening with the accelerator pedal assembly. I have a dual trace oscilloscope (with memory) so should be able to see if there is really something wrong with the pedal, but will likely have to wait until the new assembly arrives, apparently December 30 or so. In the meantime, am doing some reading and research...
#26
12-16-2019, 09:02 AM
KC0PAH LR3 sudden acceleration continues years later
My original post on this long-dead thread was 2017. About a year and a half ago I replaced both the throttle sending unit on the gas pedal as well as the throttle body and its module. I was very hopeful the problem was solved.
Well... Here we go again. this acceleration problem is even more fun in the snow. I was slowing to a stop into a parking place at work and LR3 started to accelerate and rev higher. I quickly Dropped into Park and it went to redline bouncing the rev limiter 3 or 4 times before I turned off the key. Made sure no mats or silliness on the gas pedal. Restarted the truck and it went immediately to redline. shut off. the third restart, no problem, the truck drives just fine. The truck was garaged overnight and my commute to work is less than 3 miles so nothing could have been iced or frozen either.
I love the truck and have developed a set of paranoid reflexes to deal with the issue since it is a couple of times a year intermittent issue. I guess the controlling computer is next. I am curious how prevalent this really is because I don't believe it is only the 10 or 12 trucks that I have been able to track down. I suspect many many more. If you have googled this and are experiencing the issue please post here just so we can get a real picture of the issue.
I also notice several of the crash reports are from the St.Louis area. I am wondering why that might be, as I am about 100 miles west of 3 of the 5 other reports of this I have found online digging. Correlation is not causation but is interesting.
thanks, KC0PAH
#27
12-16-2019, 09:26 AM
Hey enb54, I am very interested in what you see for triggers and voltages with a scope attached. I was thinking about building a logging unit with a Raspberry Pi just so I could catch the signal state during a high rev event, in that it is so intermittent. Since it does not throw any codes I am just very curious about what is going on electrically in this system when in the runaway condition. Especially since a couple of restarts later everything is fine again for another 6 months.
it may be interesting to note I have felt the truck start to rev a couple of hundred rpm, then change its mind. (yes all my vehicles have women's names and have minds of their own). I hover over the shifter to shut it down and it decides not to run away. Usually, this is when slowing down to park. This has always happened to me when breaking, and no my foot isn't on the wrong pedal, remember trolls it does it on restart in park with no feet on anything. My point being I believe there is an electrical or computer sensor run away condition here with some sort of parasitic feedback loop. but it isn't triggering any codes.
KC0PAH
it may be interesting to note I have felt the truck start to rev a couple of hundred rpm, then change its mind. (yes all my vehicles have women's names and have minds of their own). I hover over the shifter to shut it down and it decides not to run away. Usually, this is when slowing down to park. This has always happened to me when breaking, and no my foot isn't on the wrong pedal, remember trolls it does it on restart in park with no feet on anything. My point being I believe there is an electrical or computer sensor run away condition here with some sort of parasitic feedback loop. but it isn't triggering any codes.
KC0PAH
#28
12-16-2019, 09:48 AM
Hi kc0pah, I have not got around to setting up the testing for the accelerator pedal yet, but when I do I'll post again. My problem sounds exactly like yours, very intermittent and only happens when in Drive and stepping on the brake pedal at a stop. Have never experienced this at any other time, so it is almost? certainly an electrical problem. The first time it happened I thought someone had hit me from behind, but the second time I threw the gearshift into neutral and the engine revved up to about 5,000 RPM then settled back to idle at about 800 RPM. I now put the machine in neutral at just about every stop and experienced no more problems, but definitely do want to figure out precisely what is going on. It is odd that the brake is applied when this happens, I had a quick look at the wiring diagram and can't see any obvious connection, will have to see if the PWM signal from the ECU is wide to open the throttle (electric motor), I am starting to suspect that there is some wire chafing/shorting in a harness somewhere and that is the real problem, the throttle position sensor and the accelerator pedal both have redundant circuits, so my thinking is that they are not at fault, but I guess we'll find out by testing...
Last edited by enb54; 12-16-2019 at 10:04 AM. Reason: Spelling
#30
12-16-2019, 02:51 PM
LR3 Throttle runaway
Nearly all examples are LR3 4.4L V8 of approximately 25 posts across NTHSB and several forums and auto sites, only 2 have been the V6. all but one have been LR3 not LR4 as well.
There was a big court case I found somewhere southeast Asia, I don't remember exactly which country anymore, in which a man ran over and killed several people in a street-side cafe because of this kind of runaway in 2006 LR3.
I don't take it off-road and it does not get bounced around or dusty etc My LR3 is basically a kayak rack on wheels. It is not a daily driver either (my other car is an Audi, so I understand the myth of unintended acceleration)
That is why I keep calling it "throttle run away" :-)
There was a big court case I found somewhere southeast Asia, I don't remember exactly which country anymore, in which a man ran over and killed several people in a street-side cafe because of this kind of runaway in 2006 LR3.
I don't take it off-road and it does not get bounced around or dusty etc My LR3 is basically a kayak rack on wheels. It is not a daily driver either (my other car is an Audi, so I understand the myth of unintended acceleration)
That is why I keep calling it "throttle run away" :-)