Isuzu Problems

What you’re experiencing is the transmission calibration that many modern vehicles use to increase fuel economy. By always trying to be in a higher gear, the vehicle will record a better fuel economy number on the official test that compares it with its competitors.

The downside is that the constant upshifting means the vehicle will sometimes find itself in a gear that’s slightly too tall, and that’s when you’ll start to get the symptoms of feeling like the engine is labouring or lugging.

As you’ve noted, when the car shifts down a gear, the sensation goes away. The solution is to manually pull the car back a gear when this happens. If t really bothers you, you could ask Isuzu if there’s a software update that makes the transmission a little less eager to be in top gear.

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.

The first question to ask is have you changed the way you drive the vehicle. Driving style has a huge bearing on fuel economy, and if you’ve started to drive the vehicle harder or even on roads that are more winding and hilly than before, a jump in fuel consumption is common. On that level, is it just you driving the vehicle or is somebody else using it lately who might have a heavier foot than you?

Have you added a roof rack or more weight in the form of a winch. Even a new set of more aggressive or larger diameter tyres can do terrible things to fuel economy. But if the answer to all that is no, then you need to have the car scanned to see if any fault codes are thrown up by the computer. And when was the engine last tuned? Is the air cleaner free of dust and are the fuel injectors working as efficiently as they should be?

This sounds like a rear differential problem. The differential is designed to allow the inside and outside wheel of that axle to rotate at different speeds (which they need to do as the inside wheel describes a smaller arc than the outside wheel in a corner). If something goes wrong inside the differential, that function can be lost and the wheels try to turn at the same speed in corners. When that happens, the rear end will skip and jump about as the two rear wheels effectively fight each other.

Limited-slip differentials (LSD) often have this problem when the clutches that control the amount of lock-up in the differential fail or become worn. At that point, similar jumping and clunking noises can be felt and heard. In some cases, a limited-slip differential can be restored to health with a change of fluid and perhaps an additive, but in other cases, the unit must be rebuilt.

The rear differential in your D-Max should be the limited-slip type, but around this time, Isuzu made the LSD an option, so it would be worth checking. If it’s an LSD, a fluid change would be the first step towards sorting this problem.

The first thing to check is the fluid level in the transmission. Consult the owner’s manual for the correct method of doing this (sometimes the engine needs to be running and the transmission at operating temperature, in other vehicles everything needs to be cold, so this is important).

Low transmission fluid can cause all sorts of problems with gear selection, flaring between gears and actually making the vehicle drive, so that’s why this is the first step. If the level (and the condition) of the fluid is fine, then you need to start looking deeper, and a transmissions specialist is probably your best bet there.

The transmission is a sealed system, so any drop in the fluid level suggests a leak somewhere that needs to be fixed or the problem will return.

Beyond that, running a transmission that isn’t behaving properly can cause damage to the unit itself, so continuing to drive the vehicle in this state is not a good idea.

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.

The minimum recommended tyre pressure for your car is 230kPa. That’s equal to about 34psi in the old money. Bear in mind that’s the minimum Isuzu recommends. So 210kPa is definitely too low.

But don’t be tempted to use the tyre’s appearance as a guide to it inflation pressure. Most time, you won’t visually pick a deflated tyre until it reaches below 20psi, at which point it’s already dangerously low. Even parking on a sloped piece of road can make a tyre look underinflated thanks to the weight of the vehicle distorting the tyre’s sidewall.

Using 230kPa is the minimum, you’d definitely increase pressure if you were towing a trailer, were fully loaded or travelling at freeway speeds on a hot day. And don’t be too trusting of your tyre gauge if it’s throwing up low readings all the time. Check it against another gauge to see if there’s a discrepancy. And don’t be at all be tempted to trust the tyre pressure gauge at a service station. The modern, automated tyre inflaters are better, but the old hand-held ones are constantly left out in the weather, thrown on the ground and run over by fuel tankers.

Isuzu lifted the warranty on its vehicles to six years/150,000km for all utes sold after May 1, 2019. Unfortunately, it sounds like your car was on the road in 2018, which means it was covered by a five-year/130,000km warranty. Although you haven’t yet covered 130,000km, the vehicle is more than those five years old so, technically, the problem is not covered by warranty.

However, I think it would be worthwhile contacting Isuzu Australia’s customer service division and pointing out the car’s service history and its mileage. Isuzu may then decide to help with the cost of repairs on a pro-rata basis given the circumstances. It is not obliged to, of course, but it’s definitely worth asking.

You’ve kind of already answered your own question by saying that you’ve already waited a year for delivery. Saying no to this one and ordering another might see a similar delay and you’d be back to square one. And a year older. Like many brands, Isuzu deliveries were adversely affected by global supply-chain problems and the world shortage of silicon-chips needed to make on-board computers work.

There are two issues with a car with last year’s build date. The first of these is that the motor trade uses the year of manufacture when calculating retained (trade-in) value. So, if you don’t plan to keep the car long before trading it in, then maybe that’s a concern. If you plan to keep it for 10 years or so, then an extra birthday will have very little affect on its trade-in value by then. This is something you might be able to negotiate on with the dealership you’ve purchased from

As for warranty, Australian Consumer Law states that motor vehicle warranties start form the date of first registration, not the build date. So even though the car might technically be six months old when you get it, the factory six-year/150,000km warranty will start from the day it’s delivered to you as a brand-new vehicle. The exception to this is if the car was originally a dealer demonstrator, when the warranty would start form the time it was registered by the dealership. If that’s the case, this should be reflected in the purchase price as it’s no longer a brand-new car you’re buying.

Sandy conditions are incredibly hard on every aspect of a four-wheel-drive. The sand itself constantly shifts under the tyres and clings to them as well, dragging them down and making the engine and transmission work very hard to maintain progress. You may have already noticed that you use a lot more fuel in sandy country and it’s all because you need to be constantly making more power to maintain speed than in normal conditions. Turbocharged engines and automatic transmissions, in particular, can get very hot very quickly in sand.

With that in mind, it’s very possible that something in the driveline got hot enough for the car’s computer to go into limp home mode to protect what ever was hot from damage. Limp home mode often involves limiting engine revs and turbo boost, both of which contribute to heat production. This would explain why the car would not climb a crest but came good after a break.