Mitsubishi Problems

Even when it’s completely empty, your caravan is still likely to weigh a couple of tonnes (give or take). At which point, you’re using a fair chunk of the Pajero’s towing capacity of 2500kg. What’s happening is that the transmission of the car is choosing to shift down a gear or two to bring the engine up to a speed where it’s making enough power and torque to haul the rig along at the speed you’ve chosen to travel at. Maximum torque in the Pajero’s 3.5-litre V6 occurs at 3500rpm, so that’s what the transmission will aim for when you need maximum thrust.

The process also takes some of the load off the transmission, helping it live longer and avoid damage and overheating. There’s a general rule that says you shouldn’t really tow anything remotely heavy with the transmission in overdrive. Experienced towers physically lock the gearbox out of overdrive, and this, essentially, is what the car is doing for you by shifting down gears when a hill or headwind increases the load on the driveline.

The petrol V6 in the Pajero was never a fuel sipper, and I’m not surprised you’re seeing higher fuel consumption in this scenario. This is also the reason many people who regularly tow choose a turbo-diesel to do so.

Like anything mechanical, the gear-shifting mechanism in a car can become slack, or sloppy, over time and kilometres. Play can develop in the linkages and levers that select each gear, or in the part where the gear-shift itself is joined to those selectors. Also, the actual selectors that disappear into the gearbox and physically shift the gears can also develop excess movement or play.

You can probably remove the shifter boot and centre console inside the cabin and check for looseness in the upper part of the shifter mechanism, but to check the whole thing, you’ll need to climb under the car and feel for play and look for broken clips, missing springs and worn out bushes. The good news is that it’s probably an external wear issue and not something inside the gearbox itself.

Blow-by is a normal part of engine operation, particularly turbocharged engines where the combustion chamber pressures can be extremely high, forcing gasses past the piston rings and into the crankcase. Excess blow-by, however, suggests that there’s perhaps an overboost problem, wear in the engine or that the ventilation system designed into the emissions controls of the engine is not working properly.

The crankcase ventilation valve would be a good place to start checking as these can become very dirty and even clogged over time in a diesel engine, and a compression test of the engine might tell you more as well. The first thing to do is find another vehicle of the exact same make and model and see if it, too, has a similar level of blow-by in evidence. From there, you can decide which way to go, but either way, a good diesel mechanic should be able to identify the problem accurately.

This could be a differential problem or even something like a collapsed wheel bearing. But it’s most likely to be a seized brake or parking brake that is causing this problem. Has the vehicle been sitting around for a long time without moving? That’s a common way for brakes to seize and lock the wheel, preventing it from turning.

You might be able to knock the park brake free with a bit of persuasion, or maybe crack the bleed nipple on the brake itself to let the pressure off the brake and free it. But if the brake is rusted on, then you’ll need to disassemble it to bring it back to a condition where the vehicle is safe to drive again. Even if you get it moving again, a thorough disassembly and inspection is warranted to make sure it’s 100 per cent safe to go back on the road.

What you’re probably hearing is the pump switching on to prime the engine’s fuel system so that it starts easily and promptly. Even though the engine isn’t running, when you switch the ignition on, systems like the fuel pump all come to life to get things ready to be started and driven. When the pump has generated enough fuel pressure and volume to start the engine, it can then switch off and only switch on again once the engine is running and a constant supply of fuel is required. This could be why it only runs for a few seconds when you first turn the ignition on.

This is pretty normal, but what isn’t is if the pump starts to make a new noise or the tone of its buzzing changes. At that point, what you might be hearing is wear or damage inside the pump.

Some of these east-west mounted V6s can be very difficult to access the rear bank of cylinders. A quality workshop manual will detail how to remove the rear rocker cover and spark plugs, and there are also some very good online tutorials you can tap into.

The fact that no error codes have been logged suggests that the spark plugs are at fault. In some cases, on-board computers can detect a bad ignition lead or coil, but will not recognise a dud spark plug. But oil leaks can also cause misfires if the oil gets into contact with the leads or spark plug contacts, too, so the leaks need to be fixed as well. The spark plug theory is also supported by the fact that the miss is occurring under load, which is when an ignition system is working its hardest.

This sounds – on the surface – very much like a problem with the car’s body computer. The body computer controls all the electrical functions you’ve just listed as well as potentially being responsible for controlling the immobiliser. If the computer isn’t telling the immobiliser to switch off, you could easily find that the engine will turn but not fire.

It doesn’t work every time, but one way to reboot the body computer is to disconnect the battery and leave it overnight. This will sometimes restore the computer to factory settings (for want of a better term). If the computer is on the way out, however, this reboot may not be permanent. The other thing to check is the battery inside the ignition key. A flat or weak battery here can also mean the immobiliser doesn’t switch off and the engine will refuse to start. If none of that does the trick, an auto electrician is your best bet.

It could be dozens of things, but a transmission specialist should be able to diagnose it quickly. This is an older, well-known car and there’s not much a good Mitsubishi mechanic won’t be able to assess accurately.

But before you call a tow-truck, check the level of fluid in the transmission via the dipstick. If there’s no – or low – oil, you might have figured out why the vehicle won’t move. The job then becomes one of working out where the transmission fluid went, because these are sealed systems and shouldn’t need topping up between transmission services.

From memory, this model Triton featured a dual-mass flywheel. These were fitted to smooth out the engine and make gear changes quieter and smoother. But when they fail, they can produce the sort of symptoms you’re hearing.

Instead of a one piece, solid flywheel, the dual-mass unit is made in two parts with flexible couplings between them. These couplings absorb some of the shock of gear-shifts and engine vibrations, but when they’re worn out, the whole assembly becomes `loose’ and starts producing clunks and bangs. Replacing the flywheel is the only fix, but make sure you replace the clutch assembly at the same time. Some companies also offer a single-piece flywheel conversion for this vehicle to prevent the problem occurring again.

There wasn’t a recall for this problem on this model, but there was a service bulletin (like a recall but for a non-safety related issue). The problem was the same as yours; examples of this diesel engine were overheating. The cause was deemed to be a loss of coolant and was related to poor cylinder-head gasket sealing. In turn, that was deemed to be the result of a too-rough metal surface on the cylinder block where it joined the cylinder head and sandwiched the gasket.

Mitsubishi introduced measures such as a different coolant concentration, a different radiator cap and an ECU that gave more warning to the driver. But none of these things actually fixed the issue with the head gasket and the metal surfaces. In fact, it wasn’t until 2014 production that Mitsubishi changed the machining process on the production line to give a smoother head-gasket sealing surface which solved the problem for good.

It seems that some engines had problems while other simply did not. Hard use such as towing heavy loads or driving at sustained high speeds made the problem more likely to surface.