Engine surge again !
 

This is just a place to vent because I do not intend to start an argument regarding "pilot error". Again just a vent........I pulled into my driveway after I had hit the garage door opener and slowly approached the garage with my foot gently nudging the gas pedal (glad the door was open) and all of a sudden the the engine started to race......where upon I quickly stomped on the brake. As I firmly held down the brake the engine kept racing at a very high RPM and I mean racing. I thought I would place the gear selector into another position but nothing worked until I had moved that selector into park and still holding down the brake pedal, I watched the rpm slowy drop to normal. This was a heart pounding experience and the worst yet......this happened before but not as dramatic. I have gone over this in my mind and just can not explain it from any angle.....either mechanical or behavioral.

I would seriously look at the throttle position sensor or the ECU. See if the dealer can read any codes.

Well at least you applied the brake pedal firmly so no unintended acceleration. For future reference selecting neutral is the correct decision.

Le us know what your dealer finds in the code memory.

Hi Chuckh007 - I can imagine that would make your heart race! Glad to hear you managed to stop the vehicle without any damage done. As Jagular says, the NTSB recommends hitting the brakes (which should be able to overpower even today's high power engines) and selecting neutral. Once the car stops if engine is still revving, then kill the engine (not before you stop to ensure you have max steering and brake control).

I'm not sure which Jag you have - is it a 2009 model by any chance? I've seen a number of complaints on 2009 XF models that the brake pedel when fully depressed can go down further than the accelerator (may be true on later models too - or if you have a squishy brake pedal), so the driver's foot can catch the accelerator by accident - the harder you press the brake the more the engine revs. See the bottom entry on this website for an example, which states "has happened three times at very low speeds during parking"
Jaguar Xf - Service brakes - car safety information, failing parts, recalls, bulletins, complaints

I'm not trying to suggest any driver error - just pointing out what others have seen. You have probably also heard loose floor-mats are an issue in other vehicles but I've found the Jag ones stay in place well.

Anyway, glad that you managed to control it without any bumps!

Woah, that's just a customer complaint. ALL cars will have the accelerator pedal above the brake pedal when the brake pedal is fully depressed. That's why the pedals are in different places in the footwell.

That is really a scary experience. I certainly hope that you or the dealer can find a code, identify and fix the issue. Please let us know if you find out anything.

What year and model (NA or SC) is your car?

OK.....first the car is an 09 XF/SC and I would prefer to believe this was driver error......but I just took a look and found that the gas pedal is quite a bit lower than the brake pedal(without either being depressed).....and the brake pedal is not soft or squishy and the car does brake very well. I hope to get it to the dealer next week, for a code check.

For the engine to race without the car speeding up the transmission would have to be in neutral. This is true regardless of any braking effect. Engine speed divided by gear ratio equals wheel speed. Even in first gear (which the car will only select if you do so manually or floor the accelerator) the speed of the car must increase in proportion to engine rpm.

Therefore, what you describe could only occur with the transmission in neutral or park and regardless of the braking effected. This is incontrovertible fact needing no perception input or recollection on your part, much less code reading. Unless your car actually lurched forwards reaching a speed in proportion to the engine rpm then the car could not have been in gear.

Hi Jagular - I thought all auto boxes ran through a torque converter that breaks the direct link btw engine rpm and wheel speed. Otherwise when the car is stationery but in gear the engine would stall. Plays a similar role to a clutch in a manual box. So my understanding is the torque converter will let engine rpm climb while still holding the car stationery on the brakes when you are in gear. I'll try it tonight to confirm, but I'm pretty sure that's the case. Probably not great for the torque converter to put massive rpm through it while holding the car still, but I think it's possible. Did I misunderstand something?

True enough but every torque converter has a stall speed. I checked yesterday and this ZF seems to stall at around 3,000 rpm.

My point is that an unrestrained engine may surge if the throttle is opened or somehow an air leak bypassing the throttle plate but not the AMM develops but even an automatic equipped car will have to also lurch forward before engine rpm can exceed the torque converter stall speed.

So, depending upon the maximum rpm reached by this engine it would be possible to know if the transmission was in gear or not.

It is physically impossible for the engine to surge unless sufficient air and fuel reach the combustion chambers. That requires the electronic throttle to malfunction which is actually not possible. There is no failure mode which can open the electronic throttle. This in contrast to cable operated throttles which failed open on occasion. Most air leaks cannot increase engine rpm because there is no way for the right amount of fuel to also be injected.

I am not aware of any possible failure mode that could allow an air leak to bypass the throttle plate but still pass accurately through the AMM.

That leaves pilot error as the only possible cause.

ALL previous claims of unintended acceleration have been found to be due to human error, including those which have been fabricated. Not one instance has ever been shown to have a mechanical cause. Even the famous loose floor mats case was never shown to have actually happened.

Considering commercial airliners use variations of the same type of controls and no failures of those have ever been recorded this should surprise no one.

The problem is nobody deliberately makes this mistake so the perception of the person involved will ALWAYS be that some outside agency was the cause. The human mind is programmed apparently to seek out and ascribe causes to otherwise inexplicable events. The gambling and religious industries rely upon and exploit this phenomenon. The car industry is victimized by it, costing us all extra money to address insoluble problems resulting from this quirk of the mind.

Chuckh007,

I had posted a similar issue while driving on a highway back in November in my '12 XFR. I would send you a link, but I can't seem to find the original post when I searched for it. I was driving on I-95 near Philadelphia and it seemed that the accelerator pedal got stuck. I had my 7 year old son in his booster seat in the back - which just added to the stress of the whole situation....I feel for you and am glad that no injuries were sustained - as was the case with my experience.

I was told by folks (including those on this forum) that it was probably user error....And I found that difficult to believe. I now have a different view...

I took the car to the dealer and also spoke with an Investigator from the National Highway Traffic Safety Administration (Office of Defects Investigation)...Sent him photos, worked with the dealer, etc. We could not find anything mechanical to explain the issue. The investigator's conclusion was that the pedal got stuck on my OEM winter (rubber) mat which was not attached properly to the floor of the car. I have not had the issue since I've taken care to follow the installation of the mats more carefully. I believe now that the cause was either driver error or that mat issue (or maybe both).

Either way, glad that you're OK and good luck.

I am so sorry that I brought this up on this forum. I am a "lurker" from now on. It could have been some "foot error" on my part but the engine surge was happening while I had the brake on.....there was no car lurching forward as Jagular suggested. However, since Jagular is most always right, I will now sleep soundly and put the whole thing out of my mind. No more discussion....OK?

Your choice but there's no reason to feel that way. Nobody is suggesting your post is of no value. On the contrary, discussion of these events is valuable.

If it was driver error then it is important to realize this as a possibility and address any remedy that might occur to any of us.

Finally, if it was driver error and the error may have been caused or contributed to by an ergonomic error in design or construction then bringing this event forward is valuable.

Imagine if this thread were filled with similar descriptions, which is the whole point of these boards.

Did your dealer find anything?

From my own arsenal of driver errors I can relate a number of times I nearly launched myself through the windshield by left foot braking a non existent clutch pedal when I first got my first XF. A combination of firm pedal application and the enhanced emergency brake assist really got my attention! That resulted from my unfamiliarity with the ergonomics of automatic brake pedal shape and size, an issue of some controversy when automatics were a new idea.

Chuck - no reason to get overly sensitive due to the feedbacks received. You presented an issue that is nearly impossible to diagnose, other than making some assumptions. Assumptions are generally made from previously known experiences.

You did the right thing by posting this issue and bring it into our attention. It is scary and I hope no one else, including you, will experience it again but, if we do we have something to support a much closer look at the mechanics involved.

Albert

Just remember that ANYTHING is possible to go wrong with a human constructed device. Although it doesn't sound like it could be a possibility, some unique situation in the chain of events could have caused it to happen. Nothing is impossible!

Also, your report tells others the correct way to react to this: select neutral and keep pressing the brake pedal. You indicated it wouldn't go into neutral but you eventually got it into park, hopefully when stationary. If you managed to select park while moving and the transmission didn't lock then perhaps your transmission selector isn't working correctly.

The key points are that pressing the brake is essential as is getting the transmission out of drive.

Finally, with a push button ignition most if not all cars allow you to switch off the engine by pressing and holding down the start button for several seconds. Do this if all else fails or you are moving slowly, you lose power assist to the steering and brakes when the engine is off.

These techniques work regardless of why the engine is surging, and could save your life.

Glad to see all went well...

But had the engine surged and you been able to maintain Brake pedal pressure..the majority of your stopping power is to the front brakes, so the rears would have let go...

I think this video pretty well illustrates the mechanics and what would have happened eventually, while keeping it simple without a lot of BS....

Course, they damn kids should have their asses beat for abusing this car...probably mom's car

Yes but the car cannot move forwards because the brakes stop the front wheels.

Front brakes do most of the braking because of weight transfer effects. Rear brakes are small because weight transfer unloads the rear tires.

chuckh007 - I'm relieved to hear how well you coped!

There are other makes where this HAS happened and it was NOT driver error. Recalls and the like have been done.

Jaguar apparently use a design which removes some of the potential causes (redundant, different position sensors on each of accelerator pedal and throttle) but there COULD be failings in the control system - such as software not quite doing what it is believed it does or (say) a sticking throttle plate (I think this latter one could not create what was reported). I agree it's useful for reports to be in public because as has been posted a pattern might emerge.

Now this issue has my full attention.....it is a combination of driver mistake and mechanical/electrical malfunction. It happened again while trying to back up into a parking space and while rotating the gear selector. I will pay extra attention to my selector movement, especially in moving it too quickly. At some point the rpm took off at a very high speed and only with the brake firmly planted and the selector finally moved to park, did the engine start slowing down. I am now paying closer attention to the selector position, being in no hurry at any time. Stay tuned. BTW, still not at the dealer (50 miles away) and have family medical issues ( not me) that have taken time. Also it must be noted that the selector was replaced for all the known reasons, several months ago. Oh, and BTW when the brake is depressed all the way, it is at a lower level than the gas pedal.