ArcaMax

How much do you know about cars? It's not just trivia, either. Knowing some things about cars - or at least, some car lingo - can help you come across as more car-savvy, even if you're not a gearhead. Andthat can help you avoid getting ripped off by a bad apple car salesman or service advisor. The bad ones are looking for marks - and if you appear to know something about cars, probably, they'll save the shuck and jive for the next guy. Anyhow, back to the lingo:

*OBD II -

This acronym refers to the Onboard Diagnostics II computer (and interface) that all cars have had for about 20 years now (since the mid-late 1990s). The OBD system governs the operation of the engine and related systems. If a problem is detected, a trouble code is stored in memory - accessible via a scanning tool that plugs in to a universal port (it's the same in all cars, regardless of make/model) that's usually located near the hood release catch in the driver's side footwell area.

If a trouble code is thrown, the yellow "check engine" light in the main gauge cluster will come on and stay on, indicating the need for service.

Normally, this light only illuminates momentarily when you first start the engine, then goes off. If it comes on and stays on, it is not an emergency - you can continue to drive - but you should take the car in sooner rather than later to avoid a small issue becoming a big one.

Be aware: In states that have mandatory emissions testing, an illuminated "check engine" light will result in the car failing the test. Which usually means you can't renew the vehicle's registration - or get it, if you just bought the car used.

If you're looking at a used car prospect, note whether the "check engine" light comes on at start-up and then goes off right away. If it stays on, there could be an expensive problem with the emissions controls, including the catalytic converter. You want that resolved before money changes hands.

Be sure to drive the car around for at least 15 minutes or so, incidentally. Because it's possible someone with a scan tool (see below) cleared the trouble code(s) from memory. This will temporarily cause the "check engine" light to go out. But if the underlying problem that triggered the code wasn't fixed, the light will come on again. And if it does after money changes hands, it'll be your problem.

* "02" sensors -

If the "check engine" light comes on, a fairly common reason for that is a bad O2 - oroxygen - sensor. Take a look at your car's exhaust system. You'll see pipes and mufflers and things that kind of look like mufflers (these are the catalytic converters, which are mounted upstream from the mufflers). Somewhere forward (closer to the engine) you will also see a stubby little protrusion screwed into the piping, with an electrical pigtail on the back end of it. This is an 02 sensor - and your car may have several of them. Usually, there is at least one ahead of the catalytic converter - and one right after the catalytic converter. If your car has a V6 or V8 engine, you may have as many as four 02 sensors.

The 02 sensors sample the exhaust stream as it flows past, noting its chemical composition. This, in turn tells the OBD II computer whether the engine is running within spec and not too rich (excess gas in the air-fuel mix) and so on, which is critical for both emissions control and top performance/efficiency. If an O2 sensors goes bad, the computer is no longer receiving the data it needs - or receiving bad data - and a trouble code will get thrown and the "check engine" light will come on.

The upside is that with OBD - and a scan tool - it is possible for a technician to know whether the car has a bad 02 sensor rather than guess. The trouble code he pulls from the OBD II diagnostic port will tell him yes - or no.

You can do this yourself, too. Easily and fairly inexpensively. A hand-held OBD II scan tool costs about $120 (the better ones give you the code as well as tell you what the code means) and anyone who can turn an ignition key has the necessary skills to plug it into the OBD II port and pull the codes. Even if you don't want to do the actual repair work yourself, having the scan tool - and knowing what codes have been thrown can be very helpful when discussing your problem with a shop. You'll know, for example, that they're bullshitting you if they claim the OBD computer is telling them you've got "x" issue when you checked yourself and found the problem is actually "y".

* Transaxle (vs. transmission and axle) -

This refers to the transmission/axle assembly in a front-wheel-drive (or front-wheel-drive-based) car. The two components are bolted together, rather than (as in a rear-drive, or rear-drive-based car) mounted separately.

Usually, the transaxle is removed (and rebuilt/replaced) as a single unit if major service is required. In contrast, if the car is rear-drive, the transmission is one thing - and the axle another. They are located in different parts of the car (axle in back, transmission up front, with a long driveshaft connecting the two). If your car is a rear-drive car, the service guy shouldn't be talking to you about problems with the transaxle. And if your car is front-wheel-drive, there should be no talk of "rear axle" issues. (There are some rear-drive cars with transaxles; the old VW Beetle, for example. Also some high-performance sports cars.)

* Timing chain vs. timing belt -

Both do the same job - time the motion of the valvetrain (camshaft, intake and exhaust valves) in syncopation with the rotation of the crankshaft (which in turn is turned by the up and down motion of the pistons, which are bolted to it via connecting rods). This timing must be very accurate for the engine to run properly. Or at all.

The valves need to open - and close - at just the right moment to either seal the combustion chamber (there are eight combustion chambers in a V8, six if it's a six-cylinder engine - and so on) or allow air/fuel to enter - and spent exhaust gasses to escape.

The timing chain - or belt - keeps this dance happening by connecting the spinning crankshaft (being spun by the force of the explosions in the combustion chambers that drive the pistons up and down) to the also spinning camshaft (which rotates at a different rate). The camshaft (or camshafts, if it's a double overhead cam engine) causes the valves to open and close. If the timing is off, the valves will open too soon - or too late.

In some engines - appropriately nicknamed crashers (more formally known as interference designs) if the timing is really off, there is the possibility of catastrophic mechanical failure resulting from a valve opening (pushing into a combustion chamber) at the same moment the piston is traveling upward. If they kiss - bad news.

Luckily, there are very few crasher engines out there - and you probably do not own one. But regardless, it's important to check your owner's manual and service recommendations to see whether your car needs periodic timing belt replacements.

Timing belts are more common in Japanese/import-brand cars, while timing chains are more common in American brand cars - especially American cars and trucks withoverhead valve (rather than overhead cam) V8 engines. The chains are usually good "for life" and while they may stretch a little at some point way down the road, many miles from new, they rarely fail. Timing belts, on the other hand, will eventually fail if not replaced per the recommended intervals (it's typically every 75,000-120,000 miles). It won't hurt the engine if that happens. Usually - assuming it's not a crasher engine. But it will leave you dead in the water wherever you happen to be - and at the mercy of whatever repair shop happens to be nearby.

Better to get the belt replaced when the book says to get it replaced - when it's convenient for you and you've had a chance to shop around for the best deal on the work.

* Understeer vs. oversteer-

The easiest way to grasp these often talked-about (but rarely well-explained) terms is to talk about which set of wheels break traction first.

If the back end of the car (rear wheels) begins to slide toward the outside of the curve, the car is oversteering. If uncontrolled, the back end of the car will swing around and you'll be looking back the way you came.

If the front wheels lose traction (and slide) first, the nose of the car will try to keep on going in whatever direction inertia was carrying it - usually (in a corner) toward the outside of the curve. You probably won't experience a 180 (or a 360). You'll usually just run off the road onto the shoulder.

Front-wheel-drive cars tend to understeer because they are nose heavy - while rear-drive cars tend to oversteer because they are light in the tail.

If the car is an understeering car, backing off the throttle will help transfer some of the weight (of the car and momentum) rearward, which should help it recover traction.

Conversely, keeping on the throttle will help an oversteering-inclined rear-drive car hold its line by weighting the rear wheels, which enhances traction. But it's not instinctive to keep your foot down in a fast curve. It's something that you have to learn to do.

This by the way is why most production cars tend to understeer; in a panic situation (skid/slide) the average driver's instinct is to back off the gas. Understeering - also called plowing - is generally safer for the novice driver to deal with than oversteer.

FWD cars with transaxles tend to be nose heavy because the weight of the engine, transmission/axle (transaxle) is mostly up front while in a rear drive car, the components are spread out more evenly along the length of the car - engine up front, transmission mounted behind it (rather than bolted to it sideways) and a separate axle back where the rear wheels are.

The FWD car is usually better in snow because of that weight on the drive wheels, which enhances traction - and because the drive wheels pull rather than push the car. A RWD car is usually not good in snow because the drive wheels (the rear wheels) don't have much weight on them and so tend to break traction sooner and more easily on slippery surfaces.

========

www.ericpetersautos.com or EPeters952@aol.com for comments.