I have a 2010 XF supercharged jaguar and have had 2 separate incidents where i have my foot firmly on the brake and the car begins to lurch forward and I cannot stop the vehicle. Approximately a year ago was the 1st incident where i was stopped at a parking garage to get the ticket and the car lurched forward hitting the gate. This caused damage to the hood.

I had the car evaluated by the dealer and they couldnt find anything.

The 2nd incident occured most recently where I was stopped in traffic with my foot firmly again on the brake and the car lurched forward approximately 3 feet from the car in front of me. The car stopped when it rear ended the car in front of me which also rear ended the car in front of them. Needless to say that I am not happy.

The car is now at dealer and report has been started with Jaguar headquarters looking into this issue. I am concerned because I am now concerned about the safety of this vehicle.

I am wondering if anyone else has experienced this problem and if so what was the diagnosis and what was done to correct this issue? Thanks steve

 

In theory this is not possible. For a 2 wheel drive car it is physically impossible for the drive wheels to overcome the four braked wheels. That's the way tires work.

For the vehicle to move forward with the brakes applied the engine must apply more force to the rear wheels than the force applied through the foot brake. Since your foot is on the brake it cannot be on the gas pedal unless you routinely left foot brake (not recommended for the non expert).

When you experience this phenomenon what is your tach doing, engine rpm is what?

You should be aware that ALL cases of unintended acceleration for ALL types of car reported to suffer from this problem have occurred ONLY in North America and ALL have ultimately been traced to driver error. No mechanical cause has ever been identified.

Studies have shown that many of the drivers who reported this phenomenon were convinced they had applied the brakes but apparently did not. It is known that people can suffer from this illusion and it is thought that this is the source of the reported phenomenon.

 

Thanks for the reply. I am not sure what the rpms were? I only use my right foot and know my right foot was firmly depressing the brake pedal. Thanks dubz

 

Every person who has said this has happened to them says the same thing: that they are convinced they were pressing the brake. Turns out they were not. I'm not saying these people (or you) were lying. Just mistaken. You can get an idea of the illusion when you are stopped waiting for a light and the car next to you rolls back. You think you are moving forward, so you press the brake harder to be sure. Nothing bad happens because you aren't really moving. You only think you are.

The opposite happens if you mistakenly press the accelerator, thinking it's the brake. The car moves forward, and your natural reaction is to press harder on what you think is the brake. Of course, your car goes even faster instead. Afterwards, you are convinced the car's brakes failed in some bizzare way that made your car move forward. As noted above, it's physically impossible if in fact you were pressing the brakes.

 

its not that you have your foot on the gas, you have it on the CORNER of the brake pedal as I do and you CAN when doing this push on the brake and gas at THE SAME TIME. worse yet the harder you push on the brake the faster youll go!!! I ve done this on customer cars in the parking lot and my own. Both accidentally and on purpose to see its thats really what I did. and sure enough you can. Its really easier on the Stypes with adjustable pedals when someone has them adjusted lower for leg room.
And Ill ADD 1 more possibilty with the ZF trans. We all know about the bump when coming to a stop and Ive also had them bump when stopped which would give a little lurch if you don't have addequate brake pedal pressure for this little added torque. When you take your foot off the gas and the trans pretty much freewheels, you apply a comensurate force to the brake pedal to stop and then hold the car. Most people dont press any harder than needed to keep the car stopped. So when you get the bump engagement it reapplies power out the trans which can overcome you light brake pedal force...Just more thinking out loud...........

 

It is possible for the car to lurch forward if you have not pressed the brake pedal hard enough. It is not possible for the engine to overpower the brakes if the brakes are applied hard enough. Four wheels will always have more traction than two wheels.

Even four wheel drive street vehicles do not have enough power to overpower the brakes when they are fully applied.

 

I have same issue. Just wrote about it on a Jag forum today. When car was new dealer told me it was a fuel injection problem. never resolved and now happening more frequently. Deader flat-bedding it to shop after weekend. Mine is 2004 XJ8. I looked through jag threads and this is reported on a regular basis. Everyone will tell us it is our fault - jag certainly is not going to take responsibility. Ha! We are kidding ourselves. I either resolve now or getting rid of it. It is a danger to me and to others. You pay that much for a car and it is not safe to drive? Proposterous and shameful!

 

No need to revive a 6 year old thread in effectively a double post! https://www.jaguarforums.com/forum/x...-brake-191012/

 

Also this is a Jaguar XF forum and you’re posting about a 13 year old XJ8 which is a totally different vehicle.

 

Sorry, I am old and new at this. Sorry to intrude on wrong forum.

 

Can you elaborate on the bump. I get that often - feels like someone hit you from behind. Can anything be done to correct that - fluid/filter change?

Thanks

 

Read the threads about (or google) the lurch.

 

Hi there,

That's exactly how it's happened to me with my XF 3.0 2012!
and i thought i was the only one or that my, recently purchases jag, brakes where faulty.

I'm having the brakes pads replaced as we speak now and drums refaced as well....
not that i it would help this particular situation described in this post, the way i read it.

any input with an exact diagnosis for this faulty and dangerous error would be appreciated.

i like my beautiful XF and would love if this problem could be fixed once and for all. would certainly feel safer too.

appreciate it.

 

We just got a used XF 2016 and have owned it a month. This very thing has happened twice. It WAS NOT a slip of the foot. The car lurched forward while the brake was fully engaged. Has anyone found a solution?

 

If it lurched with the brake fully engaged then the brake is faulty (and not fully engaged).

 

But it did a really weird engine reving as it lurched forward. Weirdest thing I’ve even encountered in a car.

 

ok so im not crazy. I have a 2009 xf and it did it twice. Its 2022 any find a fix to this please.

 

That could be a brief vacuum leak.

 

is it the transmission having that little lurch forward just before complete stop ?