Hyundai Tucson Engine Problems

That’s a pretty comprehensive rebuild of the fuel system, so it’s possible that something that was removed at the time has gone back on not quite the way it was. A shuddering as you slow down suggests that the idle speed is perhaps a touch low. You should be able to adjust the ide speed fairly simply, so the first thing to try is to creep it up, say, 100rpm and see if the shudder goes away.

A mechanic will be able to do this quickly and easily. If that’s not the problem, you need to go back and double check every fitting and fastener to make sure there’s no air or fuel leak that is causing the engine to develop the staggers. Were the new injector seals treated to a dollop of rubber grease before they were installed? If not, there’s a chance that fitting them may have put a small tear in the rubber seal which is now leaking.

It sounds very much like there’s a blow-by problem with this engine. The pressure created by the combustion process is somehow getting past the pistons and into the crankcase, causing the dipstick to leave its tube and blowing oil all around the engine bay.

Blow-by is often caused by worn or broken piston rings or a damaged piston itself. But modern turbo-diesels are also prone to problems with their crankcase ventilation and emissions-control systems which can become full of gunk and not allow the crankcase to breathe properly. At which point, the same symptoms can occur.

A mechanic will be able to do some tests and determine what’s causing the pressure build-up inside the crankcase. If it’s internal wear, a rebuild may be required. But if it’s a build-up of crud inside the emissions-control systems, a manual disassembly and clean might be required. Either way, your car’s warranty might cover you for this, so the Hyundai dealer is your first port of call.

I don’t think you have anything to worry about, Yash. Oil seals often weep a bit of oil and it’s good to see that the dealership has noticed it and wants to change the seal, rather than ignore it and make it your problem once the car is out of warranty. Speaking of warranty, your car came with six years of factory cover, so even if the seal leaks again in that time, it won’t cost you anything to have it fixed.

As for your other concerns; an oil seal is not a big problem and won’t cause any other damage (unless the oil is pouring out and leaving the engine without sufficient oil (which it isn’t in your case). Changing the seal will have no effect on the rest of the car, the problem will probably never occur again (not in the 10 years you plan to own it, anyway), the seal can be changed simply without opening the engine, and the cause is probably something as simple as a seal with a small manufacturing defect or one that was accidentally `pinched’ during assembly at the Hyundai factory.

Modern cars are incredibly complex machines consisting of thousands of parts. Even the best models from the best makes can have small defects like this one. Don’t sweat it.

This is another of those "get the vehicle scanned" situations. There are about a thousand things that can cause an engine to stop in its tracks the way you’ve described, and only by scanning the computer to see what fault codes have been logged can you even begin to make a diagnosis. You cold be looking at anything from a crank-angle sensor, to a blocked fuel-tank breather, or a faulty throttle-position sensor to damaged coil-pack. Or anything in between. Modern engines are complicated beasts and the days of checking for spark, fuel and compression as a simple roadside diagnosis are long gone.

By the way, you haven’t told me whether you have the four-cylinder or V6 versions of the Tuscon. Without that information, I’m flying even blinder.

Fuel consumption is a difficult subject because there are a number of things that affect it that relate to you and the sort of driving you do, but the official fuel consumption figures come down on the side of the Mazda, 7.4 L/100 km compared to 7.7 L/100 km average for similar vehicles. Either one would be a good choice, but if fuel consumption is your determining feature then go for the CX-5.

The problem is with the cold idle speed, which should be higher than the regular idle speed when it’s warmed up. There should be a stepper motor that sets the cold idle speed higher than normal, so check that.

It's likely to be the computer detecting something wrong and shutting the engine down. Does it come back to life if you turn the key off and then try to restart? If so it's most probably the computer.