Isuzu Problems

The car could be trying to trying to tell you that there’s something wrong with the key. So start with the basics. The most common cause for the key to not operate the ignition and security system (which is why the engine won’t start) is because the key’s battery has gone flat. Change it and see if that works. At the very least, try the second key (that should have come with the car) to see if it will operate things properly.

If not, then you have to start digging deeper, at which point the cause could be a glitch within the car’s body computer which is the brain that controls everything from the power windows to the central locking and immobiliser. If that’s the case, then an auto electrician is probably your best bet, but definitely check the key’s battery first.

Not being able to match a vehicle’s official fuel consumption number is not just common, it’s something just about every owner discovers the hard way. That’s because the test that determines the number is a laboratory test, not a real world one. The test figure serves as a comparison between different makes and models, not a realistic expectation of fuel consumption.

However, the additions you’ve made to your car will all increase fuel consumption. A nudge bar and tow bar both add wight and a set of roof bars can easily add a litre of fuel to every 100km travelled thanks to increased aerodynamic drag. Even the GVM upgrade might make a difference, especially if it sits the vehicle up higher, affecting aerodynamics even further. If you’ve also fitted bigger tyres, fuel consumption will rise even more. To be honest, I reckon 10 litres per 100km is about right for this vehicle and matches most other vehicles of this type. Don’t forget, either, that an Isuzu MU-X is a much bigger, heavier vehicle than a Subaru Forester.

A car that’s left to sit for a length of time will often develop a flat battery as things like the clock and security system slowly drain the battery. But this should not happen in just three days.

If there’s absolutely no drain on the battery (as checked by your electrician) then suspicion turns to the battery itself. It may have done this since it was brand-new, but the battery could have a manufacturing flaw or internal damage that means it won’t hold a charge beyond three days. Borrow a different battery and see if the problem goes away.

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.