- The Eight Common Signs
I Need a Tune-Up?
been a couple of years since you had the car tuned up but it still
seems to be running fine. Leave well enough alone, right?
On most vehicles today, malfunctions may be camouflaged by computers
whose function is to keep the engine running as efficiently as possible
as long as possible. When they no longer can compensate for mechanical
discrepancies, they may just fail. The vehicle is disabled. Periodic
diagnostic checks and maintenance ran prevent this sometimes disastrous
Symptoms of engine trouble on most vehicles today are subtle. It's
not easy to tell if your car needs a tune-up because the symptoms
are masked by com- puterized controls. Preventive diagnosis, done
periodically, can keep your vehicle running trouble-free for years.
Short of that, if you do detect a change in your vehicle's performance,
make a note of it and report it to your technician for further diagnosis
and corrective measures.
This is the most common form of car trouble. It's usually due
to some unperformed maintenance.
If the starter cranks the engine, the electrical system probably
is ok. The culprit could be a starting sensor (on fuel injected
models) or the choke mech- anism (on engines with carburetors).
Frequently, starting failure can be traced to an electronic component
or a computer controlling the ignition system.
This noise generally is heard when the engine is under load,
such as when accelerating or climbing a hill. While it often may
be caused by a tankful of inferior gas, ignition knock frequently
is a sign your engine needs attention. It also can be caused by
a build-up of carbon inside the engine.
Late model cars are equipped with a knock sensor which "hears"
the sound and makes corrective adjustments. But it cannot compensate
for a severe mal- function, a condition which can affect engine
performance, even damage the engine.
|How long since the fuel filter was changed? A dirty filter is
a common cause of power loss. As noted under "poor gas mileage",
there can be many causes of this condition, most of which can be
located with a diag- nostic procedure.
Poor Gas Mileage
By keeping a regular check ot gas mileage (miles driven divided
by gallons used) you can tell if your engine is losing efficiency.
Increased gas consumption may be accompanied by other symptoms
listed in this pamphlet.
Poor gas mileage also may be due to:
• Underinflated tires
• Engine running too cold
• Transmission malfunction
• Dragging brakes
• Misaligned wheels
This can be caused by incorrect idle speed adjustments, a malfunctioning
sensor or switch, dirty fuel system parts, worn spark plugs or
other engine deficiencies.
Does it stall when:
• With air conditioning on?
To make diagnosis easier, make note of when it happens and advise
|This also is known as "after-run" The engine keeps chugging
and coughing for several seconds or more after the ignition is shut
off. Causes can range from inferior gas to excessive idle speed.
Carbon in the combustion chamber also may cause dieseling.
|The smell of rotten eggs comes from the catalytic converter, part
of your car's emissions control system. The odor can be due to an
engine problem or it can be a sign your car's catalytic converter
|A malfunction in either the fuel or ignition system can cause
an engine to run rough. It also can be due to an internal engine
condition, such as a bad valve or piston.
Does it occur when idling? When accelerating? At all speeds? Your
best bet: Have a qualified technician perform diagnostic and tune-up
services as needed.