2003 Nissan Maxima Looses Power In The Rain.

What causes a car to lose power while driving?

In modern cars with engine management systems, it is the system itself that reduces power if it detects a problem with the engine.  A warning light will come and and the engine will go into 'limp home' mode, where speed it usually limited to 80km/h or lower.  Any number of things can cause this, but usually it relates to loss of something important, like a coolant leak, or low oil pressure.  Sometimes it can also be a false positive due to a fault in the management system itself.All internal combustion engines require three things to work; compression, fuel and ignition.  Degradation of any one of theses will result in lower engine performance.Loss of compression can result from engine wear, common in engines with several hundred thousand kilometers on the clock.  Engine efficiency is lost because gasses can escape past the piston rings.  Mechanical failure such as a blown head gasket can cause a similar loss.Blockages or degradation of the fuel supply, such as a worn fuel pump will cause loss of power for obvious reasons.Ignition faults stem from things such as a cracked distributor head, worn spark plugs, worn ignition coil or faulty spark plug leads.  They generally result in some cylinders not igniting the fuel/air mix, thus reducing the power.Loss of lubricant or coolant will cause the engine to overheat and then seize.  In this case, loss of power is 100%.Worn bearings in the engine will usually not reduce power much, they will keep working, making more and more noise, and then fail catastrophically, causing the engine to seize.It is also possible for timing chains to slip, adjustment screws to loosen in the carburetor, exhaust manifolds to develop leaks , and other minor mechanical faults to occur that will reduce engine power.  This can happen suddenly or gradually over time.

Why would I ever use sport mode in my automatic transmission car? Will this increase fuel efficiency or is it simply a feature that makes for more fun when driving?

Engaging sport mode basically encourages the car's powertrain to favor acceleration and power over fuel economy and smoothness. For instance, if you are accelerating from a stop in sport mode, the car will hold each gear a bit longer than it would in regular mode. This helps the engine reach its maximum power output, which, for your car, falls roughly between 4000 and 6000 RPMs.Fuel economy will likely suffer somewhat when using sport mode because the engine will spend more time at higher RPMs than it would in regular mode at the same speeds.In theory, the car should be more fun to drive in sport mode, though that of course depends on what you think of as fun. One practical application would be when you are traveling in the mountains and want to have ample power available going uphill and also to hold gears longer going downhill to provide some engine braking.

What is overdrive and how should I choose between putting my car in drive or overdrive?

All the answers here are good for describing what overdrive does, but don't really give examples as to when you should use or not use overdrive.Most have said overdrive is good for highway use to reduce the RPM's of the engine and therefore conserving fuel. This is true as that is what it was designed to do.Additionally, overdrive would be safer in slippery situations where ice or wet roads may be a factor as the drive wheels would be much less likely to see a sudden acceleration from loss of grip.However, when do you not want to use overdrive?A good rule of thumb for this situation is to compare it to situations where you would find it beneficial to down shift in a manual transmission.These may include:When you are preparing to switch from a slower moving lane of traffic to a faster lane. Passing. Extended downhill grades, to prevent having to ride the brakes.Extended uphill grades to maintain power Hills when you are having trouble maintaining speed.Curvy roads where engine braking would be beneficial.TowingHopefully this helps.

Why does the steering wheel lock up while driving?

What Causes the Steering Wheel to Lock Up? | eHow Losing control of your car's steering is a terrifying experience, one that can lead to a crash with horrific consequences. If this happens to you, then you must try to bring your vehicle to a stop at once and determine the cause of steering wheel lock-up before you drive your car again. There are a number of reasons why your car's steering has suddenly locked up including:Key MechanismNot every steering wheel problem occurs when you have the transmission engaged and are heading down the road. Sometimes, drivers report that their steering wheel stays locked even after inserting the key into the ignition. When that happens, the car probably cannot be started let alone driven. More than likely the key assembly has worn out and needs to be replaced. However, before calling your auto mechanic, try to move the wheels to the left and to the right as sometimes the steering column "catches," a problem that can be resolved if you jiggle the wheel.Lock PinGeneral Motors issued a pair of recalls for the C5 Chevrolet Corvette (1997-2004 models) due to problems with locked steering. In addition to being locked while starting, owners complained that in some cases their cars could be driven but with no control of steering. This problem is due to a lock pin that fails to withdraw fully, allowing contact between the pin and lock plate. Visit the National Highway Traffic Safety Administration (NHTSA ) website (see Resources) for information about recalls #04006B and #04006C or call your Chevrolet dealer.ConclusionWhile the three causes mentioned here are among the top reasons why a steering wheel may lock up, there could be other reasons. Contact an auto mechanic for assistance, or if you are handy with repairs, consult a Haynes or Chilton repair manual (or anything similar) for guidance.

Why do you have to change a car's alternator when changing the battery?

Well, three possibilities here.One. You alternator failed, killing the battery. Replace the battery, test the alternator. You can't test an alternator with a failed battery. Start the car with the new battery, voltage should go up from 12.5ish to 13–14 volt range.Rev the engine slightly (2500–3000 rpm). Turn on all the electricals, lights, air conditioning, etc. If the voltage drops below 12.8 for more than a second, look at replacing the alternator. It should spring back to 13ish.Often alternators will have a modular regulator. Most parts shops can test and determine if the alternator itself is blown, or if it's just the regulator. The brushes may be gone, and are sometimes integral to the regulator. Either way, it's cheaper than a full alternator.If the alternator is bad — doesn't make voltage; or is weak — doesn't hold voltage: then fix or replace it with the battery.Check the feed cables and battery connections on the off chance they're bad. You should do this regardless.Two. This is a low probability. Your battery failed, killing the alternator. This can happen in the case I forget a dead short in one of the cells of the battery, or a near total loss of liquid in your battery. Either way the battery case will likely be distorted, or even cracked. It will have a voltage less than 9. It may even stink of rotten eggs, with a slight taste of chewing on foil.Three. Your mechanic is a liar and a thief who's trying to get more money out of your pocket and into his. If he says that you have to replace the alternator because the battery is bad, this is the case.