Isuzu MU-X 2021 Problems

This is probably a simple case of an automatic transmission doing what it’s designed to do. In order to keep the engine in its comfort zone (and making sufficient power and torque to haul the caravan at the speed you’ve chosen) the transmission will shift through its gears to achieve that happy balance.

Any time you encounter a hill or even a headwind (and it’s more so with a heavier caravan) the transmission will assess what speed you want to hold, and then (via changing gears) keep the engine at a speed that supplies the necessary performance. Even a hot day can cause a change in the shift patterns as the transmission aims to take the strain off the cooling system by giving the engine and easier time. Again, a big, heavy caravan will amplify this effect.

However, if the transmission is changing gears for no apparent reason, then you may need to have the calibration checked and perhaps even reprogrammed. Don’t forget, though, that a modern transmission is a pretty clever piece of gear that can even choose to shift down gears going downhill to take the strain of the vehicle’s brakes. Don’t confuse an active transmission with a dud one. And if you still think the behaviour is odd, then an electronic scan of the vehicle might provide more information.

Okay, here’s the bottom line: All engines use a little bit of oil. If they don’t there’s either something wrong with the oil pump, or the owner is kidding themselves and not checking the oil level correctly. Modern turbo-diesels also 'breathe' a little oil back through the engine as part of the emissions control system, and owners with an aftermarket catch-can system often find a bit of oil winds up in there instead of being burnt in the engine.

The question is how much is too much. I don’t think 700ml per 2000km is excessive and your dealer’s views will be based on the official figure from Isuzu. But in the real world, owners are reporting oil consumption of around a litre to 1.5 litres per 5000km. At which point, your engine is right on the money.

How you drive the vehicle and whether you tow a heavy load will also affect oil consumption, as will ambient temperature and the type of oil you use. It’s a fact that modern, lower-friction engines are designed to use a little oil in the name of saving fuel, and it’s something car owners need to get their head around. Keep an eye on that dipstick and you should be fine. Checking the oil on a regular basis will also tell you whether the engine’s drinking habits have changed; a much more valuable piece of knowledge to have.

This is an annoying but relatively common problem in many cars, not just the Isuzu. Because a car’s air-conditioning system dehumidifies the air (as well as cooling it) the water that was suspended in the air has to go somewhere. When everything’s working properly, there’s a small drain-hose from the air-con unit, through the floor to under the car where the water can be dumped with no problems.

But what often happens is that the little tube or drain-hose becomes blocked. At which point, the air from the atmosphere has nowhere to go other than inside the cabin where it causes the mayhem you’re experiencing. By locating the drain-tube and cleaning it out, the problem should go away. If not, you need to look more closely at the car’s heater matrix which also lives under the dashboard and can leak coolant into the cabin for a similar range of problems.

Unless the wheel nuts have sheared off or the bearing or axle failed catastrophically, the most usual way for a wheel to fall off a moving car is if the wheel nuts were not torqued properly by who ever removed the wheels most recently. Has the car ever had a new set of tyres? Or was the wheel that jumped ship changed at any stage because the tyre was flat?

Perhaps the best advice is to approach your state motoring club. These clubs often operate a technical inspection service where the cause of faults can be determined and a written report supplied. This is then considered an independent source of evidence and may be helpful if the matter is taken to a dispute hearing.

Even though your caravan is not at the towing limit of your vehicle, more than 2000kg still puts a pretty big load on the Isuzu’s engine. And that, simply, put, is why it’s using its gearbox to keep the engine happy and revving at the appropriate speed to safely make the power and torque you require to move that caravan at highway speeds.

The short answer is that you won’t be hurting the engine by allowing the gearbox to determine what gear it needs to be in. Quite the contrary, and over-riding the transmission to force the vehicle into a too-high gear would, indeed, damage things by overloading various components.

Short of fitting a more powerful engine, there’s not a lot you can do about this. After all, you’ve taken a two-and-a-bit tonne vehicle and more than doubled its weight (with the caravan) meaning you’re asking it to do twice as much work with the same engine. Fundamentally, you can’t beat physics.

It's true that new engines can be 'tight' and this can lead to higher fuel consumption than they achieve with a few more miles on board. And since you're almost at the 30,000km mark now, why not try the dealer's advice and see if things start to improve.

The MU-X was never the most fuel efficient vehicle in its class, but even so, 12.2 litres per 100km on the highway sounds a little excessive (although not as much as you might think). I'd expect this vehicle to return highway fuel economy figures closer to 10 litres per 100km or maybe a bit less.

However, there are several factors that might be skewing your results. The bluff aerodynamics of a vehicle like the MU-X mean that even a slight headwind can increase consumption. So can the addition of accessories such as a bull-bar and roof racks. A set of roof racks on their own can add a litre of fuel to every 100km travelled, and that's if they're not loaded. Throw a spare tyre and some gear up there and it's even worse.

Bigger (taller) tyres can also increase fuel consumption, and so can running your tyres at too low a pressure.

It sounds very much like the transmission is confused electronically or has a problem with its valve body which is supposed – in conjunction with the computer – to make decisions about what gear the transmission should be in. Perhaps it's as simple as a dodgy electrical connection somewhere and the impact of potholes or buffeting from passing trucks is causing a short-circuit somewhere.

The first piece of advice, however, is to not drive the vehicle any farther. You not only risk damaging the transmission, but it's also dangerous to drive a vehicle that might suddenly select the wrong gear at random. The second piece of advice would be to take the vehicle to a dealership and have its computer scanned to see if any fault codes have been recorded. If your local dealer doesn't want to know, take it straight to head office and contact Isuzu's customer service division.

The good news is that your vehicle is still under the factory warranty, so make it Isuzu's problem, not yours. Just make sure that the behaviour has been logged as a problem, at which point it's classed as a pre-existing condition and Isuzu is still obliged to fix it even if the warranty runs out.

I presume your MU-X is a first-generation model, not the second-generation that launched in mid-2021? The latter is engineered for a WDH, but the former is not.

Many people think a Weight Distribution Hitch (and also known as load levelling bars) will alter a caravan’s level or otherwise. But the truth is that these are really only designed to transfer some of the tow-ball loading to the tow vehicle’s front axle. `Level riders’ as they are known are more of the same. Many car-makers do not recommend or even permit the use of these hitches, so Isuzu is hardly alone there.

The problem you face in using them in direct contravention of Isuzu’s own advice is that, if there is a problem on the road, you might find your insurance company will attempt to disown you on the basis of having ignored that official advice.

When the new D-Max arrived in 2020, the big improvements included a step up in standard equipment and a big leap forward in refinement and ride quality. The engine and driveline, however, was carried over from the previous model, so performance and driveability were similar.

With that in mind, you can probably expect the all-new MU-X to offer a similar hike in standard equipment terms. But unlike the D-Max with its rear leaf springs, the MU-X already features coil springs all around, so there may not be quite the same boost to refinement or ride quality. That said, it’s unlikely Isuzu would go backwards in this department. If you can live without the creature comforts, then a run-out deal on the old model seems like a pretty good idea. It really all depends on how much importance you place on having the latest and greatest.