You might be looking at two distinct issues here. The high idle could be caused by any number of things including a dirty intake system, or something electronic. It could simply be that the idle was set too high the last time the vehicle was serviced.

This may be contributing to the feeling of the engine shuddering when you switch it off, but in reality, a lot of diesel engines exhibit this. It’s all to do with the heavy-duty nature of the diesel engine design. Because of the high combustion chamber pressures inherent in the diesel’s design, the whole thing needs to be more physically robust than a petrol engine of the same size and capacity. That means everything from the crankshaft to the con-rods, pistons and even the cylinder head and crankcase need to be made stronger. And that means more material and that means more mass.

This is why diesels generally don’t rev as high as petrol engines (there’s much more reciprocating mass) and why they can feel a bit lumpy when you load them up and even at idle. So, when you switch one off, it can feel like it’s trying to jump out of the engine bay. However, if this sensation has become more pronounced over the years, it might be wise to check the engine and transmission mounts for wear. Any wear or looseness here can contribute massively to vibrations from the driveline being passed through to the cabin.

It’s a bit hard to know what’s going on here. If a tyre is scrubbing on its inside edge, it’s often a problem with the camber settings (the amount of lean on the tyre from top to bottom). If it was realigned incorrectly, it’s conceivable that too much camber was removed and now the opposite problem is occurring where the outside edge is wearing too quickly. That said, sometimes incorrect toe-in and toe-out settings can cause similarly odd tyre wear.

Either way, this sort of problem should not be beyond the skills of a wheel alignment specialist to rectify without any mechanical changes to the vehicle or its suspension. In extreme cases, adjustable suspension bushes or mounting points can be fitted in place of the standard items to provide a greater range of adjustment. You may find that rectification is warranty issue, but if the misalignment came about through wear and tear or hitting a pothole or big bump, then it may not be covered by the factory warranty. Previous crash damage that has not ben repaired properly is also another common cause of weird tyre wear due to poor wheel alignment.

Almost certainly not. The 2016 Mazda BT-50 was a shared model with Ford (Ranger) but in late 2020, the BT-50 was replaced by an all-new model which was a platform sharing deal with Isuzu (D-Max).

Even if the dual-cab tubs of each version of the BT-50 were dimensionally similar, there would be dozens of detail differences (tie-down points, tailgate width, hinge placement, wheel-arch intrusion etc) that would mean the tub liner from one would not fit into the other. The good news is there are plenty of tub-liners available for the new BT-50. Most seem to be priced from about $300 to $500. And since the previous model BT-50 was a popular vehicle, you could probably sell the old tub liner you have to offset the cost of the new one.