Mazda 6 Engine Problems

Most mechanics will do a complete check up and tune of the engine as part of tracking this problem and it’s a good start, because a new set of spark plugs and plug leads might just fix this problem. But that won’t always be the case. As such, you could be looking at a dud sensor somewhere in the engine bay that is telling the on-board computer to shut things down or, at least, not providing the computer with enough information to keep it all running. For this reason, an electronic scan of the vehicle should also be carried out at the same time to see what fault codes are cropping up.

A prime suspect for this behaviour would be what’s called the engine’s stepper motor which is a small electric motor that controls the throttle body and, therefore, the car’s idle speed. If this motor is maladjusted or faulty, it could cause the engine to either idle roughly, too slowly, or stall altogether. But have the scan done before rushing out to spend money on parts that may or may not be the problem.

The starter motor on this vehicle is located down low on the front of the engine. Conventional wisdom is to remove the air-box and part of the intake trunking to access the starter motor's fasteners and wiring, and then remove the starter itself from below the engine bay after removing the plastic underbody protection panel. Don't forget to remove the negative battery terminal before starting any of this.

This is a known problem in the Mazda turbo-diesel, and many owners have suffered similar failures. The problem begins with the formation of hard, carbon deposits in the top end of the engine which eventually find their way into the engine’s sump and block the oil pick-up. When that happens, the engine can’t pump oil efficiently and some parts of the engine become oil-starved. That’s when a build-up of friction and, therefore, heat, will cause a catastrophic failure with the attendant metal shavings that were subsequently discovered in your engine.

So why was the problem missed? An enthusiastic mechanic will always have a look at the oil that comes out of an engine, looking for just the symptoms you’ve noted. A really keen technician will sometimes even cut the old oil filter open to check for anything that shouldn’t be there. Unfortunately, in the context of a busy workshop with price-conscious customers, this doesn’t always happen. In the Mazda’s engine, the normal practice should be to check the strainer that covers the oil pick-up, but, again, that may not have been the case with your engine. If the workshop you used was a Mazda dealership, I’d be asking management why that process wasn’t followed. Even then, it’s difficult to say whether this check would have saved your engine, as the damage may already have been done.

It’s a little higher than I would expect. It should be around 8.7 L/100 km in city driving and 5.3 on a country run. It would be worth having it checked by a mechanic or dealer to see if there is something amiss with it. It’s hard to say what the suspension noise might be, without actually hearing it I would only be guessing. Have a suspension specialist check it for you.

All of the cars you name meet your criteria of size, economy, performance and handling.

You could also add the Mazda3 and 6 to the list.

Of all of those I would nominate the Camry as the great all-rounder.

If the engine is damaged as you state the best option is probably to buy a sound used engine from a wrecker. Rebuilding the engine could cost $5000, a good used engine should be bought for less than $2000.

Stop-start is part of the engine management package and key to the car's fuel economy rating. That's why it's the default and why it can't be totally disabled. 

When doing your research you need to dig deeper and find out the claimed fuel consumption for city and country driving. The Mazda 3 manual is claimed to return on average 7.9 L/100 km, but when you look at the claims for city and country you find that it does 10.8 L/100 km and 6.2 L/100 km respectively, which lines up reasonably well with your experience remembering that the claimed figures are not real life ones like your own are.

The most likely explanation for the dealers using the 10w-30 low viscosity oil is that they have a deal with an oil company to use it. It’s more likely to be based on a commercial arrangement than anything else. Use the oil specified in the manuals and you won’t go wrong. And Mazda does approve the use of E10 in your car, so I would be inclined to use it.

Cars built after 2003, such as yours, must be fitted with a system that has been emissions approved, and I would very much doubt that anyone has mixer system that is approved for your car. The mixer system is old technology and is nowhere nearly as good as the newer injection system. Although injection systems are more expensive they are the best option.