Mitsubishi Pajero Engine 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.

This model Pajero is a bit notorious for having a crank-angle sensor that can fail over time. This is the part of the engine that tells the computer which cylinder needs to fire next, and precisely when, and if it starts to fail, that information is not conveyed and the engine will stall.

This sensor can fail gradually and intermittently too, producing the sort of hit and miss running you’re seeing now. It will often start to fail once the engine gets hot, and perhaps that’s why your car is stalling after running for a short time.

The bottom line is to not ignore it as it won’t fix itself and will eventually get worse until the car won’t start at all. At which point, you’re stranded where ever you happen to be. It shouldn’t cost too much to replace the sensor, but a mechanic should be able to tell you if, indeed, this is the problem.

This problem could be caused by any number of things to do with the fuel or ignition system, or even a sensor that is not giving the on-board computer the information it needs to light the fire. But since your car is now almost 20-years-old, there’s a very good chance that the problem is a fuel pump that has simply stopped working. These pumps have a finite lifespan, and when they stop, they often just quit on the spot, leaving you stranded.

The other possibility in a Pajero is that the crank-angle sensor has failed. Without this functioning, the computer cannot determine which cylinder it should be firing when, and that will also put a stop to play. It’s a relatively common Pajero thing.

It's not unheard of for a brand-new component to be faulty straight out of the box. However, the more logical explanation for your car refusing to start after the crank angle sensor was replaced is that the sensor was not the problem in the first place.

Instead of continuing to replace random components that may or may not fix the problem, you really need to find the problem and then tackle it with new parts. Scanning the car's electronics will often throw up the answer, but it could also be something as simple as the car having sat for a few months and the fuel going stale in the process. The causes of a no-start condition are endless.

Squeaks from the engine bay are often caused by worn drive belts, their pulleys and tensioners. You might even have a worn power steering pump, water pump or air-conditioning compressor that is giving off the odd squeak or groan. It’s worth tracking down, though, as should any of these components seize or snap, you could be left stranded.

Check around the water pump for any sign of moisture. At the bottom of the pump housing near the front of the engine, there should be what’s called a 'weep hole’. Any dampness here suggests a pump that’s already leaking and could let go any time, perhaps without further warning.

Even an air leak in any of the car’s vacuum systems (including the one that powers the brakes) can sound like a squeak or squeal, so check all the rubber lines for splits or holes and also that they’re tightly secured to their respective fittings.

Don’t forget to look for any evidence of chafing or rubbing together of various parts. This can also create odd noises.

Provided the blown head gasket is the engine’s only problem, then you can certainly squeeze plenty more kilometres from it by replacing a blown head gasket. It’s a pretty involved process, however, and requires removing the cylinder head, cleaning the surface, and fitting a new gasket. You also need to check the mating surfaces of the cylinder head and the engine block to make sure they’re straight and able to form the seal the engine requires. So, it’s pretty specialised work.

The wild card comes in the form of what else is wrong with the engine. If it’s worn internally and burning oil, for instance, it might not be worth spending the money to change the head gasket. In that case, a full rebuild or a replacement engine makes more sense.

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.

That’s pretty outrageous fuel consumption and equates to about 30 litres per 100km when 10 to 15 litres per 100km is a more realistic expectation from a vehicle like this. And that points to something seriously wrong with the way the on-bard computer is supplying the fuel to the engine.

You need to start by running some checks including the fuel delivery pressure, as well as the various sensors around the engine that determine the fuel mixture. It could be as simple as a dud engine temperature sensor which is telling the computer the engine is stone cold, even though it’s not. But equally, you could have a problem with an oxygen sensor, a throttle position sensor or even a simple vacuum leak. Even a throttle body that is not adjusted properly or a dirty mass-air-flow sensor can throw things out of kilter and cause over-fuelling.

The danger is that, if you continue to drive the vehicle as it is, you’ll not only go broke putting petrol in it, but you might also damage the engine through the excess fuel causing damage to the cylinder bores.

There are literally dozens of reasons the check-engine light might illuminate in a car like the Pajero. Fundamentally, the car is trying to tell you something is not right with one or more of its systems, and that it needs attention. Those systems could include (but are not limited to) the ignition, fuel, emissions, exhaust, mechanical and cooling systems.

Simply replacing random parts is a quick way to burn up a lot of money and still not fix the problem. I’m curious as to why you’ve assumed the problem is with the EGR system. And even if you’re right and the EGR system is causing the problem, you might find the fault is with the actual EGR valve or its coolant system, rather than the electronics that control and monitor it.

Take the car to a workshop and have it electronically scanned to try to narrow down the cause of the check-engine light. The fault codes will have been logged by the on-board computer and are usually the only way to zero in on the actual problem. Even once that’s done and the problem fixed, there’s probably a separate procedure for switching the engine light off.

Unless your engine is overheating very quickly and then miraculously cooling instantly, I’d say there’s a problem with either the temperature gauge itself or the sender/sensor unit that controls it.

An auto electrician will be able to test the gauge and its sensor and tell you what’s happening. Scanning the vehicle electronically might also reveal the cause as the onboard computer may have logged this odd reading as a fault code.