Ask The Guide

Air-conditioning relies on fans as well as the actual refrigeration system to move the chilled air around the cabin. If the fan isn’t working, that won’t happen. So a check of the fan in question would be a good place to start. Perhaps there’s a wiring fault, maybe the fan is intermittently failing to kick in.

There’s another possibility, too, and it’s more common than you might think. Some air-con systems tend to build up ice inside the system’s plumbing. If that happens, you’ll suddenly get no air-con and possibly even zero airflow through he vents as the ice blocks the trunking completely. The solution is to turn the system off at that point, allow everything to thaw and then turn it back on. Try that process next time the vents fail to see if that fixes it (temporarily).

Since you’ve been driving manual cars for many years now, you’ll be aware that some gearshifts are just better than others. However, none should be causing you to apply lots of force just to select a gear.

You could be dealing with a worn clutch which is making selection difficult, or a selector mechanism (cables, linkages and pivots) that are worn or have run out of lubricant. Even the adjustment of the shift cables can cause a problem like this.

I’d start with lubricating everything that connects the gearstick to the transmission and work the lever through the gears a few times to see if the lubricant makes any difference. If not, you might have to dig a bit deeper, checking for frayed shift cables of frozen joints. If you’re really unlucky, you may have wear or damage inside the gearbox that is making it difficult to select first gear.

But in the meantime, you can try this trick. When you’re stopped at the lights and ready to select first, instead of going straight for that gear, slip the lever into second for a brief moment and then try for first. Sometimes, this can assist selecting first, as you’re using the synchromesh on second to help with engaging first. This is often a great trick for a worn transmission.

If the engine is not getting hot and the temperature gauge is reading normal, it’s difficult to see how the coolant could be boiling. Perhaps what you’re seeing is the coolant in the overflow bottle bubbling, which can appear as though it’s boiling. But the reality might be that you have a leaking cylinder head gasket.

When that happens, gasses from the combustion process can escape into the engine’s coolant system and appear as bubbles in the overflow system. And to the observer, that can look very much like boiling coolant.

Either way, you need to find a good workshop that can check this stuff and figure out what’s really going on. Only then can you diagnose the root problem and tackle it.

Rule of thumb says the correct on-road pressure is somewhere between 30 and 40psi for tyres like these. But since you’re losing traction regardless of inflation pressure, who knows. Clearly something else is going on here. Just for starters, the MU-X is fitted with both traction control and stability control which should rule out losing traction in the first place. Are these systems working? If not, you’re technically driving an unroadworthy vehicle.

How old are the tyres? Were they fitted to your previous vehicle and swapped over to the new one? Tyres have a finite lifespan beyond which the rubber compound starts to degrade and the tyres lose grip. That’s something to check. Perhaps the rubber has been contaminated by something like oil or grease. Has the vehicle ever been parked in a pool of oil or diesel? It sounds pretty daft, but is the fuel tank or filler neck allowing diesel to leak on to the tyres or flick up on to them as you drive?

You also need to be aware that as an off-road tyre, on-road grip will never be as good as a tyre designed to work mainly on bitumen. The tread pattern and compound are both compromises in the interests of going off-road, so you can’t expect passenger-car tyre grip from a tyre like this one on a vehicle like your Isuzu.

This make and model of tyre seems to be pretty well received among users, although some have mentioned a lack of wet bitumen grip as something to keep in mind. Don’t forget, either, that in really wet or greasy conditions, you can safely switch to high-range four-wheel-drive to prevent wheelspin and improve your safety margin.

It’s possible that the same problem is causing both the check engine and oil light to light up. That’s because a low oil pressure or oil level light will sometimes trigger both the oil and check-engine lights. I assume the basics such as oil level (on the dipstick) have been checked.

Continuing to drive a car with a flashing oil light on the dashboard is asking for trouble, to be honest. This needs to be investigated and you might want to look for another dealership who can better manage this stuff.

Either way, it’s a dealership problem because this sort of thing should be covered by the factory warranty if there really is a problem. But even if it’s just a computer glitch that’s lighting the warning lights up now and then, you need to know what that is and put it right.

I’m amazed that you managed to find such a convoluted reset procedure, even if it only provides a temporary fix. You may well be right that this behaviour is linked to heat build-up, especially if it happens after several hours of driving.

It’s interesting that you mentioned the engine sometimes goes into limp home mode, because the transmission’s behaviour sounds a lot like it’s going into limp home mode, too. Limiting the gears the vehicle will select is a classic symptom of limp-home mode, in fact.

The real question then becomes, what’s causing it to do so. Limp home mode can be initiated any time the vehicle thinks that continuing to drive at full power or speed will do further mechanical harm. As such, there’s a huge range of things that will cause limp home mode to engage, including a leak somewhere in the turbocharger’s plumbing, low coolant level, low oil pressure, low fuel pressure, a faulty sensor and many more.

So the first job is to scan the vehicle and see what fault codes are thrown up by the computer. From there, you can home in on the actual problem and fix it. But without those codes, you’re kind of flying blind.

On this model, the sensor in question is located on the crankcase (not the cylinder head as many are). You’ll find it on the driver’s side of the crankcase, below the intake manifold. Replacing it involves removing the old one by screwing it out, and screwing the new one in. But there’s a bit of a process for this, and if you’re not familiar with this type of job, it’s probably one for the experts.

The sensor is located between cylinders three and four and it’s located pretty close to the manifold. The good news is that you don’t need to remove the manifold to access the sensor; you can get to it by going into the engine bay through the wheel-well.

Don’t forget that you’ll lose some coolant in the process, so that will need to be topped up with the correct type afterwards. Remember, too, that the new sensor won’t work unless you correctly reattach the wiring plug that connects the sensor to the rest of the car. This area can be pretty grimy and muddy in a vehicle like this, so cleaning everything off first is a good idea.

This model Hyundai i40 had two different automatic transmissions depending on which engine was fitted. If you have the petrol engine, the transmission will be a conventional torque converter six-speed automatic. However, if your car has the turbo-diesel engine, the transmission will be a seven-speed dual-clutch unit. At which point things change.

These dual-clutch units (and not just Hyundai’s) have shown themselves to be a bit under-engineered in some respects. And when they start to develop wear in the clutch packs, they can definitely start to behave poorly including rough shifting, shuddering when moving off and other problems.

But either way, you are going to need the services of a transmission specialist to determine what’s wrong. Even if you have the conventional automatic version, you might still find it has serious internal wear or failures, but only a detailed diagnosis will tell you the whole story.

On the other hand, you might be lucky and simply have a transmission with low fluid level that will be restored to health by a top up of that fluid. You’ll still need to find from where it’s escaping, however, as this is a sealed system and should not lose fluid over time.

The 160Z was not a car we saw in Australia and, I believe, was more or less a South African-only model. Australia’s closest relative would have been the 120Y Coupe. As such, I’m not too sure about the way the fuel lines were routed from the fuel pump to the carburettors, but in the case of the larger 240Z Coupe which also used twin carbs, the fuel system in the engine bay consisted of a common fuel rail with rubber hoses leading to each carburettor.

So, for the pressure to be uneven in the two carburettors, you’d probably need to have a restriction or blockage in that rubber line or a problem with the needle and seat of the carburettor in question. The thing is, I’m not sure how you’d know you had a pressure differential unless you’d fitted an external pressure gauge to each carburettor’s supply line, as Datsun certainly didn’t provide such a gauge.

Perhaps you mean you have unequal vacuum at each carburettor and this is a much more common scenario. You can check for this with a vacuum gauge, noting whether one carb is `pulling’ more vacuum than the other with the engine running. From there, you can use the adjustment screws on the carburettor to match, or 'balance' the two carbs so they contribute the same effort in making the engine run.

This sounds simple, but it’s actually a job for a specialist who understands old carburettor designs and how to make them work properly. It’s a bit of a dark art, but rally workshops and mechanics that specialise in classic cars are a good place to start looking.

By the way, my information suggests that the carbs on your car are made by Hitachi and, therefore, are more likely to be a Japanese copy of the SU carburettor that has been turning motorists into mechanics for decades.

You’ve probably already figured out that the two codes mean you potentially have two separate problems, but either one of them could cause your car to switch to limp home mode. In any case, they both need to be fixed.

So, let’s start with the PO118 code. This suggests you have a faulty engine coolant temperature sensor. When this fails, the computer isn’t getting the information it needs to know whether the engine is cold or warmed up. As a result, the fuel-air mixture will be all over the place and the vehicle will possibly use more fuel and run poorly as well as being hard to start in the morning.

The other fault code you’re seeing, PO489, is to do with the engine’s exhaust gas recirculation valve. This valve channels some of the engine’s exhaust back through the combustion chambers to reduce tailpipe emissions by burning the same gasses twice. Your car’s computer will be constantly opening and closing this valve, but it’s an electrical signal (from a sensor) that tells it when to do so. If this sensor has failed, that information won’t be getting sent to the computer and the check-engine light will come on.

Both of these faults will probably be fixed by replacing the sensors in question, but until they are replaced, the car will continue to throw fault codes and switch to limp home mode.