Ask The Guide

There are many reasons this could happen, and they could be mechanical or electrical. An engine that revs freely with no load on it, but goes weak at the knees when a load is placed on it, could be suffering from poor fuel supply, a faulty ignition system, internal wear, a blocked exhaust or even a worn driveline that is creating excess friction. You could even have a seized brake or something equally fundamental going on.

But it’s also true that the car’s computer can send the engine into what’s called limp-home mode if it detects a serious problem. Limp-home mode limits the amount of power the engine can make or how fast it can rev, as a means of protecting it against further, more serious damage. Perhaps that’s what’s going on here. Certainly the symptoms match that diagnosis. The best advice is to have the car electronically scanned to see what fault codes are thrown up by the computer. Only then do you have a decent starting point on where to look for the root problem.

You might be looking at two distinct issues here. The high idle could be caused by any number of things including a dirty intake system, or something electronic. It could simply be that the idle was set too high the last time the vehicle was serviced.

This may be contributing to the feeling of the engine shuddering when you switch it off, but in reality, a lot of diesel engines exhibit this. It’s all to do with the heavy-duty nature of the diesel engine design. Because of the high combustion chamber pressures inherent in the diesel’s design, the whole thing needs to be more physically robust than a petrol engine of the same size and capacity. That means everything from the crankshaft to the con-rods, pistons and even the cylinder head and crankcase need to be made stronger. And that means more material and that means more mass.

This is why diesels generally don’t rev as high as petrol engines (there’s much more reciprocating mass) and why they can feel a bit lumpy when you load them up and even at idle. So, when you switch one off, it can feel like it’s trying to jump out of the engine bay. However, if this sensation has become more pronounced over the years, it might be wise to check the engine and transmission mounts for wear. Any wear or looseness here can contribute massively to vibrations from the driveline being passed through to the cabin.

If the problem goes away when you restart the car, it’s reasonable to assume that there’s something electronic that’s responding to the rest, or there’s something like a crank angle sensor that is getting hot, delivering bad information to the computer and then working fine again once it’s cooled down.

Have you had the vehicle scanned for fault codes? This should probably be your next step rather than simply changing more components that don’t turn out to be the problem. Meantime, don’t rule out things like the spark-plug leads or even a failing fuel pump. How about something from left-field. I’ve personally seen a dirty fuel filter allow a car to run perfectly for the first 10 kilometres, until the gunk built up on the filter element and stopped the fuel flow. Switching the engine off and then back on again, allowed all the rubbish to fall away from the element and the car would be perfect for another 10km. Until it wasn’t.

A dirty or clogged fuel filter will stop a modern turbo-diesel engine dead in its tracks. In fact, it’s one of the first things a switched-on mechanic will check on vehicles like yours. So if the mechanic has changed the filter and restored to car to full health, then I reckon he or she has probably nailed the cause and fixed it very simply and cheaply for you.

Let’s be honest; there are literally thousands of things that could go wrong that might make your vehicle stop. Modern cars are very complex things, but you need to have faith that sometimes, simple problems occur and can be fixed simply.

The Territory is pretty well known in the fixit trade for having various transmission problems. Perhaps the most common was a failure of the entire transmission due to coolant from the transmission cooler mixing with the transmission fluid inside the gearbox. When that happened, the destruction was fairly complete with ruined electronics and internal hardware as the contaminated fluid could no longer satisfactorily lubricate the gearbox’s many moving parts. A whole new transmission was the usual outcome.

The first sign of this was usually milky transmission fluid (caused by the water mixing with the oil) but by then, the damage was often already done. This was more of a problem with the later model Territories with the six-speed ZF automatic transmission.

What you haven’t told me is whether your car has an automatic or manual transmission. And that means different things if the transmission has somehow been over-filled.

In the case of a manual gearbox, you’ll find that the extra oil will probably soon be evenly distributed across the bottom of your car as the excess exits the scene through either a breather tube or a seal or gasket.

But if it’s an automatic, the extra fluid could cause the entire transmission to behave strangely, as this type of gearbox relies on the correct internal fluid pressure to select gears, change gears and, in fact, make the car move at all. Again, though, the extra will probably force its way out through a seal or gasket and then you have a much more complicated repair to make.

The best advice is to check the level of the fluid as set out in the owner’s handbook and make sure the level is correct before driving anywhere else.

Noises are impossible to diagnose without actually hearing them. So you need to take the vehicle to a mechanic and get the car to produce the noise you’re reporting. That may involve leaving it overnight or otherwise reproducing the circumstances under which it misbehaves. Experienced mechanics can often tell whether a noise is important or just wear and tear, and act accordingly.

For the record, your mystery noise could be anything from a worn turbocharger, a sticking hydraulic lifter, piston slap, bearing knock or even something as weird as a loose baffle in the exhaust system. All these things can manifest as random and metallic noises, and they range from simple to catastrophic in magnitude.

This is not an uncommon problem with the head unit in a lot of makes and models. Like any other computer-driven piece of equipment, they have a finite lifespan and, once they’re done, they’re usually done for good. That’s why the dealer would be recommending to replace the unit rather than tyring to fix the one you have.

What a lot of people do is that this opportunity to upgrade to a newer, better head unit with better sound, better connectivity and more up to date apps. There’s loads of choice in the aftermarket and you can spend as little or as much as you want. Many owners also use this as a chance to upgrade speakers and perhaps add a sub-woofer or extra amplifier for much better sound. And you’re right; if the original unit died, a replacement of the same type may well have the same problems.

The first thing to do is get your mechanic to drive the vehicle when it’s hot. Arrange a time and then deliver the car at that time with everything up to full operating temperature. Otherwise, the problem isn’t going to show up when it needs to.

While there are lots and lots of things that can cause this sort of behaviour, it does sound like something in the actual powertrain is the problem. That’s because the shuddering goes away when you drop the transmission into neutral and let the vehicle coast to a stop. If the problem was a wheel, a wheel bearing, axle, brake problem or an out-of-balance driveshaft, the problem would continue even though you were coasting.

You may have a problem with something inside the transmission itself, way too much backlash somewhere in the driveline or a problem with the torque converter. Either way, you need to have your mechanic experience the problem or everybody is simply guessing.

This is actually more common than you might think in cars with this type of rotary knob gear selector.

There are a couple of major causes. The first is a blown brake light or brake light switch, believe it or not. Many modern cars are set up so that unless the driver has their foot on the brake, the car won’t move out of Park. If the brake light switch (or sometimes even the brake light globe) fails, the car doesn’t get the message that the brakes are applied and the car won’t shift out of Park.

The other possibility – and it’s not unknown on Range Rovers – is a flaw in the circuit that turns the knob’s twisting action into an actual gear selection at the transmission. A specialist might be able to take the circuit apart and replace the blown component, restoring operation to normal.