Category Archives: Automotive

Specs for maximum performance and efficiency

Actually, there is no such thing as a tuneup in the traditional sense of replacing parts to bring the ignition and fuel systems up to specs for maximum performance and efficiency, and there hasn’t been for years.

About the only things left from the traditional tuneup are new spark plugs, which is typically done every 100,000 miles, and replacing the air filter periodically. The federal EPA and Department of Energy say that replacing a clogged air filter will not improve gas mileage but can improve acceleration 6 to 11 percent. The agencies do not say what benefit can be derived from fresh spark plugs, but computers that control today’s engines adjust the air-fuel mixture and spark timing to compensate for wear, such as when the electrodes on spark plugs are worn down.

Even so, some car owners still dutifully take their car in periodically to have it “tuned up.” Instead, service technicians will inspect and perhaps test the fuel, ignition and emissions systems to look for faulty vacuum hoses,oxygen sensors and other parts that can hurt performance. The federal government, for example, says a bad oxygen sensor can give engine computers false readings and reduce fuel economy as much as 40 percent.

Having your vehicle serviced and inspected periodically is a good way to extend its life and keep it operating efficiently. However, walking into a repair facility and asking for a tuneup is a bad idea because it indicates you’re still living in the previous century and have extra money you would like to spend. Some in the auto-repair business will take advantage of those opportunities.

Are You Need a Valve Clearance Adjustment

It could, depending on the age, condition and brand of vehicle you’re driving. The maintenance schedules for some recent Hyundai engines, for example, call for a valve clearance inspection at 60,000 miles. Some Hondas call for an inspection at 110,000 miles. Some manufacturers advise valves should be inspected only if there is excessive valve noise. Others don’t mention valve clearance in their maintenance schedules.

Valves are opened by camshaft lobes on overhead camshaft engines and by rocker arms on pushrod engines. With extended time and use, the original clearances between these parts and the valve stems become bigger (with exhaust valves, the clearance can become tighter over time). That often leads to a clattering noise or more engine vibration that a driver might not notice for quite a while, because it increases gradually.

Intake valves open and close to let the air-fuel mixture (or just air in some modern engines) enter the combustion chambers, and the exhaust valves allow exhaust gases to escape. Too much or too little valve clearance can result in poor performance or a rough idle because the engine can’t “breathe” normally and operate at peak efficiency. Too much clearance means the valves will likely clatter and, over the long term, cause damage to the valves and/or camshaft lobes or rocker arms. If there’s too little clearance the valves won’t fully close, causing excessive heat, and the engine will lose power.

If your engine generates a loud clatter, it could be time for a valve clearance adjustment — though on some engines the valves don’t generate noise when there’s too much clearance. Loss of power could be a sign of a weak or broken valve spring, and a tapping noise could be caused by a loose rocker arm, so a clearance adjustment may not be all that’s needed. The mechanic won’t know for sure without inspecting the valves.

Because adjusting valve clearance (or “lash”) requires removing the valve cover (or covers on V-type engines) and checking both intake and exhaust valves, it isn’t a quick in-and-out maintenance item like an oil change, especially on engines that have three or four valves per cylinder. Plan on at least a few hours at the shop and a charge just for the inspection.

The Crankshaft Position Sensor

Most owners probably don’t know that their vehicle has a crankshaft position sensor until the engine dies, won’t start or starts running poorly. Then they find out they need a new one.

The crankshaft position sensor, typically mounted near or on the crankshaft, tells the engine computer how fast the engine is running. That’s so the control unit knows when the spark plugs should ignite the air-fuel mixture and, in some engines, when to inject fuel. These sensors are used on virtually all engines that have distributorless ignition systems.

If the sensor fails, the computer won’t know how to set the ignition timing, so the engine may stop running or refuse to start. It could also stall or run badly, possibly triggering the check engine light. Excessive heat is a frequent reason these sensors fail, and they also can stop working because of faulty electrical connections or wiring.

Some vehicles also have a camshaft position sensor that allows the engine computer to monitor the position of the camshafts (or camshaft), which open and close the valves, for more precise fuel and ignition management.

These sensors are not listed as routine maintenance items, but they often fail without warning. For that reason, some repair shops recommend they be replaced on high-mileage engines as preventive medicine.

The manufacturers recommendations

Maybe forever, if you rely on an overly liberal interpretation of the maintenance schedules set by some vehicle manufacturers. That doesn’t mean you should ignore them or even accept the manufacturer’s recommendations, though; instead, add them to your list of items that should be checked annually after the first three or so years of ownership.

With accessory drive belts, most manufacturers recommend only a periodic inspection for cracks, fraying or other visible wear, and on some GM vehicles the first inspection isn’t until 10 years or 150,000 miles, when someone else might own the vehicle.

Hoses? What about them? Most owner’s manuals don’t even mention radiator or coolant hoses (except that they can get really hot on an overheated engine). Other hoses, such as for the power steering or air conditioner, usually are mentioned only as something that should be checked as part of routine maintenance or when leaks are suspected.

Coolant hoses typically last several years, though anything longer than 10 years may be pushing the limits. Rubber weakens with age and from repeated exposure to hot coolant, so the older they get the higher chance they’ll leak and cause the engine to overheat.

Drive belts are usually the serpentine type that snake their way around pulleys to power the alternator, air conditioning compressor, power steering pump and perhaps the water pump, and they’re designed to last several years.

When to replace a drive belt is a judgment call by a repair technician, and it’s up to the vehicle owner to decide if the time is right given the manufacturers have largely chosen to stay out of it. We would err on the side of caution, because when a drive belt breaks your car comes to a halt. Depending on where this happens and when, a belt that fits your car may not be available until tomorrow, leaving you stranded.

Regular Void the Warranty

Using regular gas in an engine that requires premium could void your warranty. That is most likely to happen if using regular causes severe engine knock or pinging (premature ignition of the fuel, also known as detonation) that damages the pistons or other engine parts.

For example, here is what GM says about the subject in an owner’s manual for a vehicle that requires premium:

“Use premium unleaded gasoline with a posted octane rating of 91 or higher. If the octane is less than 91, you could damage the engine and may void your vehicle warranty. If heavy knocking is heard when using gasoline rated at 91 octane or higher, the engine needs service.”

Note that this applies only to engines that require premium gas. Some manufacturers recommend premium gas but say that regular or mid-octane gas can be used instead. They usually warn that using lower-octane gas could reduce performance. When that happens noticeably, or if engine knock occurs, they advise to start using premium.

The computers that manage modern engines are able to adjust the ignition system to accommodate lower-octane gas — to a point. With regular gas, fuel economy and acceleration will likely deteriorate at least slightly. Because regular has lower octane, it is more prone to detonation. Burning regular in an engine designed for premium on a long-term basis or under heavy loads can cause engine knock, and that in turn can damage the pistons, valves or spark plugs. Due to the presence of knock sensors and the car’s ability to retard the spark timing, you might not hear knocking, but that doesn’t mean premium is unnecessary.

Radiator and Cooling System Problems

If steam is pouring from under your hood, a temperature warning light is glowing bright red on your dashboard or the needle in the temperature gauge is cozying up to the High mark, it’s time to pull off the road and shut down the engine before it fries from overheating.

Any indication of overheating is a serious matter, so the best course of action is to shut down the engine to prevent further damage. Driving a car with an overheated engine can warp cylinder heads and damage internal engine parts such as valves, camshafts and pistons.

Even letting the engine cool for an hour and topping off the radiator with a 50-50 mix of antifreeze and water may not fix what’s wrong. Here are some reasons an engine will overheat:

  • The coolant level could be extremely low, because of long-term neglect or because a leak has developed in the radiator or radiator hoses. Coolant circulates inside the engine block to cool it, and the leak might be in the block, or from the water pump or heater hoses. Old coolant loses its corrosion-inhibiting properties, allowing rust to form and ultimately causing damage.
  • The thermostat that allows coolant to circulate may be stuck in the closed position or a clog may have developed, perhaps from debris in the cooling system.
  • The engine cooling fan has stopped working or the radiator’s cooling fins are clogged with debris so that the air flow that reduces the coolant temperature is restricted.

Get Me Better Mileage and Better Performance

Several aftermarket manufacturers sell engine air filters that they claim provide better airflow and increase horsepower and acceleration as a result. Some of these companies have many loyal customers who swear that they have benefited, particularly in performance, from using these high-flow filters.

These filters are often made of cotton or nanofibers, and some can be cleaned and lubricated with a special oil and then reused, with at least one brand guaranteeing they will last a million miles. Others can be cleaned with an air hose and reused. Many are designed to directly replace the stock paper air filters provided by the vehicle manufacturers; others are included in a freer-flowing air intake system that delivers more fresh air to the engine.

On the surface, these claims make sense. Engines are like athletes in that the better they can breathe, the faster they can go.

However, independent tests have found that these aftermarket filters may provide little or no performance benefit, and some types allow more dirt into the engine. That dirt will get into the engine oil, and the abrasive effects can damage internal engine parts. In addition, some users say that  the oil sprayed on some of these filter types gets into the engines’ air intake systems as well.

The EPA has not tested oil-bathed filters or other free-flow air filters, but it has conducted tests that compared clogged conventional air filters against new ones. The EPA found no significant loss of fuel economy from a clogged air filter but did find in a test of gasoline-powered vehicles that acceleration improved with a clean air filter.

Is It Good to Use Premium

The only guaranteed result of using premium gas in an engine designed for regular is that you will spend more money. As far as any tangible benefits, the chances are slim to none.

If your engine runs fine on regular, filling it with premium is unlikely to boost acceleration or fuel economy by more than insignificant amounts. No matter what you’ve heard, premium won’t do more to clean deposits from your fuel injectors or other parts of the fuel system because today’s regular gas contains the same detergent additives.

The main difference with premium is its higher-octane rating, 91 or higher compared with 87 for regular. The higher octane gives premium gas greater resistance to early fuel ignition, which can result in potential damage, sometimes accompanied by audible engine knocking or pinging. Higher octane allows engines to have higher compression ratios (for a more energetic explosion), more advanced ignition timing or forced-air induction like turbochargers or superchargers. They perform best when fed premium gas.

But if the vehicle manufacturer says your engine needs only 87-octane regular, that is what you should use. The higher octane of premium gas won’t make your car faster. The opposite is possible, because higher-octane gasoline technically has less energy than lower-octane; it’s the fuel’s ability to be compressed more without pre-igniting that results in more power when used in the appropriate engine. Premium gas is not “stronger.”

If you burn premium because you think it makes the engine peppier, that is probably psychological: I’m paying more, so I must be getting more. Some motorists claim they get better fuel economy with premium, but some of that could be due to favorable weather conditions (such as warm weather instead of cold) or other factors.

If you use premium because your engine knocks on regular, you are treating the symptom, not the cause. Something else might be causing the knock, such as carbon deposits or hot spots that should be diagnosed and treated by a mechanic.

Turn opens and closes the valves

The timing belt is a notched rubber belt, sometimes called a Gilmer belt. This belt allows the crankshaft to drive the camshaft, which in turn opens and closes the valves. Without this belt, the engine can’t run.

How do I know it’s time to replace my timing belt?
A loose or worn belt will cause ticking or rattling noises, poor engine performance and overheating, usually triggering the check engine light. If the timing belt breaks, the engine can’t run — and on some engines that break can cause internal damage. Most engines have timing chains, which typically don’t require replacing.

How often should I replace my timing belt?
The schedule for replacing a timing belt varies by manufacturer, with some saying it should be every 60,000 miles and others 100,000 miles or more. Changing the timing belt requires removing many other parts, adding to labor costs. If the timing belt drives the water pump, many mechanics recommend replacing the pump at the same time.

Why do I need to change my timing belt?
It’s not a question of why, but a question of how often, based on the recommendations of the vehicle manufacturer or a mechanic who finds the belt is stretched or damaged. See above for mileage recommendations, but remember: If it’s broken, you’re engine simply won’t work.

How much should I pay?
The cost of repairs can depend on where you are as much as it does on what you need fixed. To get an estimate for your repair, go to our estimator, plug in your car’s year, make and model information, add your ZIP code, and choose the repair you need. We’ll give you a range for what your repairs should cost in your area.

The Minimum You Should Drive

We recommend driving every two to three weeks to make it less likely that you wind up with a dead battery, flat-spotted tires or other issues that can be caused by letting a car sit for weeks.

We’ve heard many people say they let their cars sit for months with no problems, but you’re better off driving it a couple of times each month and for at least 10 miles, with some speeds over 50 mph if possible. You not only want your engine to get fully warmed up but for the entire car to get some exercise as well.

Letting a car idle for 10 minutes will get the engine up to normal operating temperature but accomplish little else. Driving the car for several miles wakes up the transmission, brakes, suspension, power steering, climate system (including the air conditioner) and all the fluids, seals and gaskets for those components that have been on a long snooze.

Batteries slowly lose their charge when they sit idle, and starting the car will drain it even more. That is one reason you want to drive several miles afterward, so the battery has a chance to recharge. If a car sits for a month or more, the battery may lose so much power that it will need a jump-start — or a  charge before the engine will start. To be sure your car will always start, consider a battery tender as described in our guide, “How to Store Your Car for Winter.” Unlike the rechargeable batteries in electronics, conventional car starter batteries don’t like to cycle deeply, so keeping them topped off could improve their longevity.

Here are more reasons not to let your car sit for several weeks or longer:

  • Tires slowly lose air under all conditions but especially during cold weather. As they do, the weight of the car keeps pressing down on the tires, which causes flat spots to develop on the segments sitting on the ground. Driving the car and adding air if necessary will usually make the tires round again, but letting the vehicle sit for extended periods on underinflated tires can cause permanent flat spots that you will be able to feel and hear when you drive.
  • Rodents might take up residence under the hood or even in exhaust outlets. If they get hungry, some may munch on the wiring harnesses and other parts made of soy and other organic materials that are used on modern vehicles.