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Engine Tune-Up 2003
05/23/12
You're cruising down the highway in the left lane at a pretty good clip. Traffic
is heavy but moving steadily. All of a sudden you see your exit coming up and
you have to get over quickly. There's a break in the traffic flow and you put
your turn signal on.
You hit the gas and try to move into the right lane but you're too late. A
1972 Volkswagen Micro Bus trying to do the same thing beat your big V-8. It
was right in back of you but was able to move into the hole faster than you
could. So you swerve back into the left lane, drive 37 miles to the next exit
to make a U turn.
After your wife gets done dealing with your five kids in the back seat asking
"Are we there yet?" she suggests it may be time for a tune-up. But
today's engines are computerized, have 100,000-mile spark plugs and don't need
to be tuned up, right?
Well guess what, you're wrong.
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It is true we haven't had to replace ignition points and condensers for over
20 years. If it's a 2001 or newer vehicle, you may have a non-replaceable fuel
filter under the hood. You have a maintenance free battery and the ignition
timing is non-adjustable. However, while a lot has changed in the last seven
or eight years, the idea of a tune-up is anything but gone.
The Federal Government has tightened emission laws but our air is still full
of dirt and dust. Eventually your air filter will plug up and your engine will
starve for air until you decide to replace it. They took the lead out of gasoline
so your spark plugs don't get lead fouled anymore and the new high tech spark
plugs last a lot longer then there earlier ancestors. However, they don't last
forever and your engine will derive great benefit if replaced well before the
manufacturers recommendations.
Under Hood Checks
The best way to start a tune-up on today's engines is to access any codes that
may be stored in the Powertrain Control Module (PCM) with a code reader or scan
tool. Just because the Malfunction Indicator Lamp (MIL), such as a Check Engine
Light, Service Engine Soon or Power Loss light, is not on doesn't mean there
are no malfunctions found or codes stored.
The MIL only comes on when a malfunction occurs that directly effects emissions
and on the systems it was designed to check. Most Diagnostic Trouble Codes (DTC)
will only show up with a code reader or scan tool. In addition, it is not uncommon
for many "No Code" problems to arise.
If there is a DTC, you should check the whole circuit to locate the problem.
If you get a DTC "P0185 Fuel Temperature Sensor B Circuit Malfunction"
don't assume it means a bad Fuel Temperature Sensor. While eight times out of
ten it is, there is a 20% chance it is a burnt wire or bad connector terminal.
While it's not too bad to gamble with a $20.00 part, it is an entirely different
matter when a $900.00 distributor is indicated.
Another thing to be careful of is mis-interpreting a DTC. A DTC of "P1130
Heated O2 Sensor (HO2S) 11 At Adaptive Limit" may sound like a bad HO2S,
but what it's really saying is "Hey, I've corrected as much as I can. This
problem's worse than I can compensate for." So you need to look for a problem
in the fuel delivery system because the HO2S is doing its job correctly and
replacing it is just throwing $100.00 out the window. It's like your wife telling
you your car is on fire and you go out and get a new wife.
Okay, so you checked for DTCs and there were none. Now what do you do? The
first tool to use is your eyes. Look under the hood for damaged or disconnected
vacuum lines, loose or dirty connections, cracks in the large air intake hoses
or a loose, burnt or disconnected ignition wire.
You can still do some basic checks of the engine controls and sensors. If you
engine has timing marks, you can check the ignition timing with a timing light
to see if it is within specifications. Always refer to the under hood emissions
label for the proper procedure for checking ignition timing. If there are no
timing marks, you can use a scan tool to check the ignition timing.
Set your scan tool to Timing Check and read the timing. Gradually open the
throttle to about mid-range and look for a smooth, steady increase in ignition
timing. If it is not smooth and steady, it may indicate a loose timing belt
or timing chain.
If the timing is good, you can check the Throttle Position Sensor (TPS) and
Mass Airflow Sensor (MAF). These, too, should show a smooth, steady increase
as the throttle is increased. If there are any voltage spikes or dips, the sensor
is bad. You can also tap the TPS and MAF to see if there are any voltage spikes
shown on the scan tool or hiccups. If there are, then the sensor is bad.
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