Recently, our 2011 LR4, which we have owned since new, has developed a habit of accelerating hard when at a stop. The motor suddenly revs up taking significant pressure on the brake pedal to stop the vehicle from lunging forward. Before anyone says, make sure your foot isn't on the accelerator, that is not what's happening. After 11 years of ownership this has only become a recent phenomenon, having happened a few times in 8 months.

Anyone running into the issue of runaway acceleration?

 

I haven’t heard of this symptom before, but possibly the idle control valve or throttle position sensor (throttle body). Otherwise, maybe a vacuum leak. Does it idle slow when in park? When the car starts sucking unmetered air, the RPMs can shoot up a bit. Maybe check your PCV valve and your brake vacuum booster pump and lines. We’ve seen many reports of that booster pump failing - usually its reported as an oil leak, but it probably could cause a vacuum leak as well.

 

Thanks. It does have a slight vacuum leak from a warped passenger side valve cover. Will check for other possible causes.

 

This issue was pretty bad for me soon after purchase.
- I think I might have temporarily fixed it by resetting the transmission adaptation values on the Gap Tool

I still see this issue from time to time which makes me think I dont think its only a software fix.

 

Interesting. It's been happening with more frequency on this vehicle. Still need to address the warped valve covers, but aside from that it's a wild goose chase.

 

Hello,
I am not sure but I think we are talking about the same problem. I posted something some months back
https://landroverforums.com/forum/lr...ts-own-108865/

Currently my car is still at the garage and so far the mechanic has replaced the injectors and they are looking in to replace the ICU. The explanation I got so far from the mechanic is that my car ( the ICU) was set for petrol in Europe, and as I brought it over to Laos (Asia) it would not be used to the lower quality petrol here and the ICU regulated the injectors as with clean fuel, and this would have messed up the system.
If anyone reads this and has better ideas, please let me know. Thank you in advance

 

@RicVTE: Is your car a diesel or a petrol model? The post above suggest it’s a petrol car, but your earlier post that you link to says its a “TD” which would be a turbodiesel.

If it’s a petrol car, I don’t see that your mechanics theory about the quality of gas makes much sense. Poor gas will cause some knocking, but the difference in unburned oxygen (which is what the fuel control is based on) would not be enough to cause higher RPMs by any appreciable amount, and certainly would not cause your car to accelerate suddenly. I would be looking first to the throttle control system (accelerator pedal sensor, throttle body and throttle position sensor). A big vacuum leak can also cause an increase in RPMs when at idle.

If it is a diesel, I don’t know too much about them, but I understand you can get a runaway condition if the cylinders are getting fuel or oil from any source. Diesel engines will run on oil, so if you have a turbo leaking oil into the air intake, for instance, that can cause acceleration from what I understand. And, if you have put petrol in the diesel engine in the past, you can cause all kinds of problems.

 

hello jlglr4
Thank you for your message and input and sorry for my belated response. Indeed it is a Diesel . So far all interventions have not fixed the problem and the car keeps on doing it. Now the mechanic wants to open the motor as he thinks it may be a problem with a piston gasket. I am not sure as the car has yet a relative low milage of about 80.000 km .

All ideas are welcome

 

I just replied to a similar question in the LR3 group, my problem seemed to be a poor electrical ground for the electrical reference circuit to the accelerator pedal (gasoline/petrol engine). My LR3 accelerator pedal has 2 potentiometers which are used to ensure that there are no differences in what the driver's intentions are. Unfortunately, in my case these potentiometers (pots) are referenced to a common ground, and that might cause difficulties if the ground circuit is compromised, just a suggestion...

 

Update on my end. Replaced the two PCV valves located on the left side valve cover and it may have soled the issue. The motor is breathing easier and is smoother overall. There is a rubber diaphragm located in the housing that can fail.