Uncontrolled acceleration!

[janousek]

Hi all,
I could find anything similar hence I want to get this tread started.
This is what my wife told me. She was returning from work yesterday, she tried to overtake a car on a hill. When she push the accelerator pedal the car hesitated but then picked up the speed and jumped forward. The pedal somehow got stuck pressed and car kept accelerating.
In panic, she applied brakes which did not help. Then she went into button pressing frenzy and managed to get pedal released and slow down the car - she didn't use the emergency brake though - apparently she never knew. I know there is a bit of ambiguity here but this is the best I got out of her. One thing she is sure, cruise control was not on. she took the risk and drove about 2 km to home without any incident.
The car will be towed to mechanic soon and I will update the results. But meanwhile I am looking froward to hear from anyone who experienced similar symptoms.

its 2015 RRS SDV6 HSE - no previous faults.
rgds

[justinc]

Sounds like a runaway to me, do not drive again until the oil level has been checked!

[Graeme]

A nasty experience!

Pressing both the accelerator and the brake pedals is valid so a stuck accelerator pedal mechanism for whatever reason could be the cause. Applying the EPB is programmed to cancel the accelerator but understandably not the first option to try unless its remembered.

[Graeme]

Sounds like a runaway to me, do not drive again until the oil level has been checked!
Accumulated oil in the secondary turbo perhaps? Enough for runaway until it was all gone?

[janousek]

Sounds like a runaway to me, do not drive again until the oil level has been checked!

Thnx for the quick reply, so the correct term to use is "runaway"?
Above statement immediately set me off checking the oil level and about an hour through investigation I firmly concluded that LR forgot to install an oil dipstick to my wife's car!...
ok I figured all out after a while, apparently there is no dipstick in these engines, all digital. Based on electronics oil level is perfect. but again how can you trust a digital reading, the only way to verify is to drain and refill the oil.

[Graeme]

I built a small module that closes the throttle butterfly on my 4.4 TDV8 for a short period when the ignition is switched off as a way to stop a runaway engine because switching off normally wont stop it. It's quite easy to fit one to a TDV6.

[jtmesa]

how about the carpet mats? sometimes the mat itself catches the pedal if the mat isnt secured to the floor of the car.

[Pedro_The_Swift]

standard servicing on a Toyota is checking on placement and security of drivers floor mats,
has its own checkbox! [bigrolf]

[justinc]

Unless the d4 has aftermarket footwell deep rubber mats, and she is in the habit of holding the foot hard to the floor up a hill, then the pedal being interfered with by a mat will not be a factor... I'm still concerned for a fuelling or even a failed turbocharger allowing engine oil into the engine to be a possible cause.
The dealer will be able to check all history of the vehicle operations, down to time of day , degree of throttle applied and even air temperature and load on the engine via their software diagnostics. Hopefully an answer is forthcoming.

[janousek]

I built a small module that closes the throttle butterfly on my 4.4 TDV8 for a short period when the ignition is switched off as a way to stop a runaway engine because switching off normally wont stop it. It's quite easy to fit one to a TDV6.
Hi Graeme, would you tell us more about this module but dumb it down pls so ppl like me can understand what involves.

[Graeme]

The wires to the EGR throttle butterfly motor are intercepted so that the butterfly motor can be powered, isolated from the ecm supply, for 15 seconds after the ignition is switched off although aborted if the ignition is switched back on. A double pole relay ensures no feed-back to the ecm. The wires can be readily intercepted near the throttle housing on the 2.7/3.0 but not so readily on the 4.4 so mine were intercepted at the ecm plug. Ignition and permanent 12V power via a fuse plus earth are also required.

The EGR butterfly is normally used to deprive the engine of fresh air to increase recirculated exhaust gases though the engine to decrease oxygen content. One of the European car manufacturers, which IIRC is Audi, added the closing of their EGR throttle butterfly on their diesel V8 on engine shut-down to rid the engine of compression roughness in the final second or 2, a smoothness that I immediately noticed on my 4.4 TDV8.

It appears from DTCs (fault codes) for the 3.6 TDV8 that the 3.6 TDV8 ecm will do the same trick if it detects uncontrolled engine operation but no equivalent DTCs exist for the 2.7, 3.0 or 4.4 engines which have all suffered self-destruction from runaway.

[janousek]

I went CSI with matts.
There are 2 floor mats in this car, a loose rubber matt on top of a pinned carpet one. I could not see those how matts can interfere with the pedal mechanics though.
I tried moving the rubber matt with my feet, it requires considerable and purposeful effort to slide the matt forward and there is no way it would slide on top of the pedal. I also placed the rubber matt on top pedals but but again it would not have enough weight to keep pedal pressed and go unnoticed by the driver.
IMO it was not the cause.
I am hoping the LR mechanic would come up with plausible explanation and definite fix otherwise this car is not safe to drive, out of warranty and not sure what would be the next steps...

153477

[Graeme]

Did your wife get the feeling that the accelerator pedal was actually stuck down or was that an assumption from the continued acceleration?

[janousek]

Hi Graeme,
She is sure that the pedal was down and later on she also felt it got released with little thump.
We are still debating what might have worked at the end and she now thinks she pulled the park brake.
Thnx

[DiscoMick]

She probably didn't think of it while panicking, but would moving the gear selector into neutral have been possible or would it have refused to shift because the engine was racing?

[Graeme]

There is no difficulty in shifting to neutral under load.

My L322's throttle pedal assembly is operated by an almost vertical rod passing through a rubber grommet, but there is a considerable gap down which a small stick or stone could fall that might jam the mechanism. My L322 is 4 years older but I don't know if the gap has recently opened-up or if it has existed for some time.
If it is possible that the pedal jammed then it should be opened and checked or replaced.

Edit: Your accelerator pedal is suspended from above so not at all like my L322.

[janousek]

Just an update,
The worst has happened, after in and out of mechanic for various readings and tests, the results is inconclusive.
Simply cannot replicate the problem or determine the cause.
We will continue to monitor...
Thnx