Was driving down a city street and stopped to let an angle parker back out, and all of a sudden the engine accelerates while I have my foot on the brake, threw the transmission into neutral and the engine revved up to about 5,000 rpm then back to idle (800 rpm). Anyone else experienced this "Audi" syndrome? This happened once before, it is within about 5 minutes of starting, has never happened after the machine has been running for 15 or 20 minutes. I'm thinking maybe one of those capacitors for the RF filters (fuel injectors or transmission solenoids) may be starting to fail so perhaps I should order them both? The previous owner was the 2nd owner and he only had the machine for 50K before the engine timing chain cassette cratered, so does not know if those capacitors have ever been replaced. The machine has appx 254,000 Km (157,000 miles) on it and no error codes displayed and/or any that can be read by my IIDTool BT.

 

Neither capacitor would have anything to do with it. You need accelerator input for it to rev.

 

Not necessarily so - it is "fly by wire" control to the throttle body so a voltage applied to the wire could give a similar problem. I would be looking for a chaffed wire somewhere.

 

OK, so the throttle pedal pot or something similar? I'm confused because this has only happened before about 10 minutes of warmup, never after. It is strange that it never happens after 10 or 15 minutes of driving... I sure don't want to drag out a portable oscilloscope to check this out, but will have to if it keeps up, unfortunately it is an intermittent problem...

 

Could be a dry joint that heats up and works okay till it cools down

 

Well, I am sure hoping that's the general direction of what it is, just so strange that it only seems to happen within the first 5 or 10 minutes of driving. I do not want to pull apart the wiring in our Canadian winter, but hopefully more symptoms will pop up to help isolate the problem...

 

Throttle Position Sensor, but I can't figure the cold temp piece of the puzzle.

 

OK I'm going to investigate it a bit more deeply, has only happened twice since engine replacement about 5K Km ago, will have a peek at some of the electrical connectors this weekend...

 

Does the LR3 have a crankshaft position sensor (CPS)?
On my Disco 2 I had quite a few sudden acceleration moments right after I swapped out a new Duralast CPS. Luckily I had my foot on the brake when it strangely accelerated at stop lights. I swapped out the Duralast sensor for a Bosch sensor and all was well ever since.

 

Yes the LR3 4.0 V6 has a CKP mounted on the ZF automatic transmission bell housing at the 11 o'clock position when standing behind the engine (very hard to access). After reading up on the operation of the CKP though, I don't see how it could control the engine speed on the LR3, since if its output goes low then the engine automatically shuts off. Reading the technical literature it would appear that somehow the accelerator pedal position assembly (APP) or its wiring are a bit off, but then the ECU and throttle body should have put the machine into "limp home" mode and generated a check engine light and code. The throttle is basically a DC motor controlled by the ECU outputting a PWM (Pulse Width Modulation) signal which in turn is detected/generated in the ECU by a varying 0-5 VDC signal from 2 circuits connected to the accelerator pedal APP assembly. Will attempt to check this out on the weekend, it is unfortunate that this problem is intermittent. Thanks for your ideas...