I know this is a car forum and not everyone works with radio transmitters so I will use general terms because there is no need to get all "sciencey".

Are these sudden accelerations occurring in an urban or rural environment?

Having ran high power HF/VHF/UHF transmitters on my Land Rovers, I can tell you with confidence that despite the best efforts of the Ford engineers, these cars are susceptible to outside Radio Frequency Interference getting into the wiring (RFI ingress).

Part the randomness (is that a word?) comes from what we call high level mixing (of frequencies). If there are two or more radio signals that are strong enough and produce a harmonic signal near the car, it could emulate the electrical signal that resembles the one from the pedal and trigger a random movement of the throttle body. Often time moving a few meters will change the signals and the interference will stop.

Not something you can test or diagnose with any automotive equipment. In our modern society there so much RF floating around that some cell phone companies are experimenting with ways to capture it to run the phone rather than have a battery that need recharging.
No telling what can happen.

Jeff

 

Well, after checking the wiring for chafing, voltages, grounds and carefully examining the wiring diagram, all I can deduce is that the throttle body valve motor operated for some unknown reason and that caused the engine to respond accordingly. I have ordered a brand new LR006814 throttle body as a careful read of the electronics involved indicates that the potentiometers used (TP sensor) may have a tendency to wear and mine has 290K on it so for $300 I'll give it a shot. The only 6 pin TP sensor I could find was for a Toyota forklift and the existing one is riveted to the throttle body so replacing just the TP sensor was not an option. The intermittent saga continues...

 

Hi Jeff,
I am a long term high power RF type of person (Radar in Air Force) and a long time radio amateur, plus I have an IFR 1200 communications monitor (etc) and have attempted to diagnose what you have described. Unfortunately, in electronics we all have found out that usually the simplest solution to a seemingly complex problem is the answer after looking for all the technically complicated ones, so I've tried playing with the radio frequencies, grounds and reference voltages, now going for a brand new throttle body assembly, we'll see how that works out. Thanks for your input and I'll be sure to post on any results after the snail mail throttle body from Montreal arrives...

 

Well all, I am now a bit red-faced because I was carefully looking over the wiring diagrams and NOT reading the text in the maintenance manual. The wiring diagram shows a resistive bridge for the throttle position sensor but reading the text tells that all the LR3 vehicles use 2 Hall effect sensors for the throttle position sensors, which are immune to mechanical wear and rear. I guess I'll have a spare throttle body, I'll install the new one when it gets here, but I'm not confident it'll fix this pesky problem. I sure wish it would throw a code, but so far no trouble codes...

 

Well, replaced the throttle body yesterday and went for a test drive but unfortunately, we were in the fast (left) lane when a tractor trailer with a low boy was merging and just we became parallel with each other something flew off the other guy and blew out our passenger side front door window, showering my wife with glass. Luckily, although it scared the ******* out of us, no cuts and we managed to stop and drive down into the ditch, we are so lucky! Anyway, we'll keep all informed...

 

Yikes, sounds super scary! Hope she's ok.

 

Yes, pretty scary, sounded like a bullet but of course it wasn't, a sackful of tempered glass vacuumed up and luckily a local shop had a window in stock but I can't seem to get the back of the holder to snap in to the carrier, going to go to the shop on Monday and figure that out. Still no problem with the acceleration issue, I'm supposing that it may come back at some unexpected time in the future, but it is a strange one...

 

Hi all, here it is about 10 months later and it happened again today! I was making a right turn and had to immediately stop for some bicycle riders who were crossing the street when the engine suddenly took off, I shifted into neutral and the rev limiter took over and brought the engine back to idle. I'll keep looking and reporting, this is awful darned strange...

 

Hello all,
It happened again... I started the LR3 today in my garage, waited the 55 seconds or so for the rpms to drop from approximately 1300 to 800, put my foot on the brake to put the machine in reverse and the rpms shot up to very high and then back to normal. Looks like this problem can happen in "Park" also, and is so intermittent that it is nearly impossible to diagnose, again no fault codes noted. I will try to look harder at the wiring diagrams for some common wiring which would point me in the correct direction, but I'm starting to think there's a problem with the ECU, I've replaced everything I can see that appears to be common except the ECU, this is just the weirdest...

 

Looking very carefully at the wiring diagrams I see that if there is any kind of problem with the wiring at the steering column clock spring interface you'll experience intermittent failure of the cruise control and perhaps this is what's related to my crazy intermittent but still persistent unintended acceleration problem. I am also now seeing a DTC P0579-00 (Cruise Control Multi-Function Input A Circuit Range/Performance) on my GAP tool so I'll be going down this path soon, seems like I have a serious health issue to deal with first. Am not looking forward to removing the airbag and pulling the steering wheel but it is cheaper and easier than replacing the ECU. Unseasonably warm here this past week, plus 12 C (54 F) at the end of January!