2004 Chevy Blazer

Daytime running lights was voted into a Canadian law several years back and required all new vehicles to be equipped with running lights that were automatically turned on during daylight hours. This automotive technology was developed with safety in mind.

In the United States General Motors was one of the first companies to also make this standard equipment on all GM vehicles that were sold in North America. My 2004 Chevrolet Blazer is equipped with daytime running lights. And they have not been completely trouble-free.

For one thing they are on so much that they experience more bulb failures than any other bulbs all my truck. There is also quite a lot of heat generated from the bulbs being on all the time. This can eventually melt the bulb sockets and the plastic lenses and housings that they are mounted in.

How daytime running lights work

On some vehicles they use the high beam lights as dedicated daytime running lights. The control circuit is connected directly to the vehicles ignition switch so the lights are turned on whenever the vehicle is running. The circuit is usually equipped with some type of module that lowers the power to the high beam so that it can burn with less intensity.

When the headlamp switch is moved to the headlight position the module is deactivated and the lights work with their normal intensity and brightness. On my 2004 Chevrolet Blazer there is an optical sensor mounted on the top side of the dash panel. During the day the sunlight is detected and the daytime running lights are turned on automatically.

Daytime Running Lights

When it starts to get dark the ambient light sensor turns on the headlights on low beam intensity automatically. My 2004 Chevrolet Blazer also has an override in case the system malfunctions.

Also note on Chevrolet vehicles that when you apply the parking brakes this will also deactivate the daytime running lights even if the vehicle is running. So if you set your parking brake and try to check your daytime running lights this will not work.

On some vehicles the daytime running lights may not come on until the vehicle is put in drive. Keep these quirks in mind when you are trying to check the operation of your daytime running lights. As for me when I check them I usually pull up to a wall or a garage door so I can see the reflection of the lights. This will work on most models and is a good way to tell if one of your daytime running lights is blown.

If your interested in more automotive articles this next link will take you back to the main page for the auto repair blog from this post about daytime running lights.

Timing Tester

Improper ignition timing can cause several car problems. Anything from hard starting to lack of power might be traced back to the root cause of incorrect base ignition timing.

In rare occasions I have also seen a hard start condition from this as well. Often when people are having poor performance from their engine they may wonder if it is an issue with the engine timing.

You have to remember that poor engine performance can also be caused by poor compression, overheating, incorrect valve timing that can be caused by a timing belt that slipped one notch. Clogged catalytic converters and probably about 20 other things can also cause this condition.

How to test for improper ignition timing

When the ignition timing is not correct there are a few tests that can point to the car problem. The main symptom of a timing issue would be incomplete combustion at different engine speeds. Incomplete combustion can cause an excess of oxygen in the exhaust stream.

In this case the powertrain control module will try to compensate for this imbalance of the air fuel mixture by changing the injector on time to straighten out the mixture. If you have a scan tool that can read the data stream you can pull up the fuel trim mode and see if the computer is forcing the injectors to stay on longer or shorter.

If you have exhaust gas analyzer such as the kind that is used by automotive shops and inspection stations you can sample the exhaust stream and read the amount of oxygen. You can also pull up the oxygen sensor data stream on your scan tool and see if the voltage is changing properly.

Vacuum test for incorrect timing

The vacuum gauge is inexpensive and handy device that can quickly perform a few tests that can help diagnose lack of power problems from clogged exhaust among others. Incorrect ignition and valve timing also affects manifold vacuum readings. If you connect your vacuum gauge to a strong manifold vacuum source and low readings are observed you can adjust the base timing to see if the readings are able to be brought back into specifications.

Another telltale sign of a timing problem would be excessive engine ping. Engine ping is referred to as cylinder pre-ignition. This is when the air fuel charge is ignited at the wrong time. If it is ignited before top dead center it can cause the valve train to generate a noise that is known as engine ping.

In most cases engine ping is caused by timing that is too far advanced. If the timing is too far retarded the most likely symptom would be a hesitation lack of power and very poor fuel economy. I am working on an article about using a timing light to check for improper ignition timing. It should be ready for my next weeks post here on the auto repair blog.

Distributor Cap and Rotor

This post is for people that still have a distributor cap and rotor ignition like me instead of the more modern ignition systems such as direct ignition or coil on plug type systems. Some vehicles including my 2004 Chevrolet Blazer still use a distributor cap and rotor to fire off their spark plugs.

This type of ignition system can cause car problems like an engine misfire or shudder under load. Caps and rotors have been around for a long time and for the most part they are extremely reliable. There is no shame in having a distributor ignition.

Sure your friends may say your vehicle is old-fashioned as they point and laugh at you while you’re in the parts store buying replacement parts. When this happens remind your friends that your cap and rotor only cost $28 while their individual coil that has failed might cost $200. A direct ignition coil and module assembly could cost around 350 bucks.

Problems with cap and rotors

The reason I’m writing this article is that I continue to see a common problem that develops on vehicles that use a distributor cap and rotor ignition systems. This would be moisture and corrosion that can build up inside. Back in the early 1990s the 4.3 Liter engine was extremely susceptible to this type of corrosion.

Bosch Distributor Cap

Technical service bulletins were created by General Motors to make technicians aware that the vent on the base plate could become clogged and accelerate the moisture buildup and corrosion inside the distributor. Not only would this damage the cap and rotor but it could also affect the ignition module.

The module connections can turn green and even disintegrated if the problem is not addressed. The technical service bulletin informed technicians that they needed to check that the vent screen and the base of the distributor was clean and allowing moisture to be vented out.

Just about every distributor that I checked in the early 1990s was experiencing this problem. When the cap was removed it looked like it snowed inside the distributor. Often it wasn’t until the vehicle was towed in for a no start condition that the problem was identified.

More problems with rotors and distributor caps

You should also make sure the distributor cap is properly seated on the base plate and all clips and screws are tightened securely to provide a good seal to keep moisture out. It is a good habit to inspect the distributor cap and rotor and check for physical damage and also corrosion build up inside.

Other types of damage that needs to be inspected would be electrical damage from high voltage. You can check for burned metal terminals and also carbon tracking inside the distributor cap. Carbon tracking is the formation of a line of carbonized dust between distributor Terminals or between a terminal and the distributor housing. Carbon tracking indicates that high voltage electricity has found a better path over or through the plastic.

The result can be car problems such as a misfire or shudder under load due to the spark plug firing at the wrong time. You can check the outer Towers and metal terminals for defects. Although distributors are usually well protected sometimes you find cracked plastic that may warrant replacement. You should also inspect the distributor rotor for a buildup of corrosion on the tip that passes voltage to the terminals of the cap.

Although you can take an emery board to the tip of the rotor to clean it I usually recommend replacing it because a distributor rotor is only about six dollars. For more information about solving car problems and the latest posts from this auto repair blog visit the homepage from that last text link. I recently wrote a page on my other website about no starts and no spark. If you have a no start condition and are interested in learning how to test for spark take a visit.

My Toolbox

Most people bring their vehicles into a professional auto repair shop because they believe this will be the fastest and most cost efficient way to get their vehicle back on the road. In a perfect world this is absolutely the case.

As an automotive consumer you should be vigilant and ask questions to make sure your auto repair shop is holding up their end of the bargain (even if you trust the shop).

This is more important when you are paying for things such as check engine light diagnosis or even when you are trying to get drivability problems repaired that require pinpoint troubleshooting.

If you go in for an intermittent stalling condition or rough running car problems the way that the shop handles the troubleshooting and diagnosis can affect the total cost of the repairs. Your repair shop should be using a standardized diagnostic method that brings them to the failure in an orderly and efficient manner.

If the mechanic starts guessing at what is wrong and begins to replace parts he hopes will fix the problem this will add dollars to the repair bill. This is the exact opposite of the reasons that you brought your car in four professional auto repairs.

Professional mechanics don’t guess

When car problems baffle an experienced mechanic they know where to go and what to do. This can vary with the symptoms of the automobile that they are trying to repair. But in general it would be consulting vehicle specific publications.

Diy repair manuals

Professional and Diy mechanics have access to a mind blowing amount of information. Symptom charts and technical service bulletins can put the mechanic back on the path of efficient auto repairs.

A good mechanic also knows that it is Okay to discuss the vehicle’s problems with other technicians, shop foreman and other experienced coworkers. For smaller shops technical assistance is also offered by phone and Internet.

If a mechanic feels like asking for assistance will hurt his pride or damage his reputation he could wind up going down the path of replacing parts that are not needed (guessing). If they are electrical components then they will not be returnable.

In the end the customer winds up paying for parts that were not actually needed. Sadly in this situation the shop and the mechanic may cover up the fact that these parts were replaced in error.

Ask questions about the auto repairs

When you go to pick up your vehicle examine the parts and labor break down closely. If the information provided to you is not clear ask that it be explained. Take a look at the list of parts that were replaced. In general one car complaint should equal one part replaced.

TPS Sensor

This is not always the case! But ask questions if it is not the case. Let me give you an example. If a dealership mechanic replaces more than one warranty covered part per complaint the repair is reviewed by the factory. The reason being is that the factory knows that in most cases one complaint equals one part replaced.

If you brought your vehicle in for a rough running condition and there is a list of four or five electrical components such as throttle position sensor, oxygen sensor, idle air control motor, EGR valve, egr solenoid then you need to find out why so many parts were used to fix one complaint.

Remember that you are paying for professional auto repairs. You should not be responsible for unnecessary repairs, parts that were not required to fix your complaint and the training of shop mechanics.

If you are interested in more information about this subject visit my auto-facts.org website and this page that talks about the auto repair business. For more of the latest posts to this blog this next link will take you to more auto repair information.

Rough Running Engine

Let us not forget that the engine runs rough condition can be caused by basic car problems. Many times professional and do it yourself auto mechanics start searching for answers in the vehicles high tech areas.

In many cases, the car problem is located in the most basic principles of engine operation.

Not all engine performance problems are directly related to on-board computers, throttle position sensors, fuel injectors or other fancy electronic systems.

This is the reason that all types of mechanics will still need to understand basic engine operation, as well as time tested engine testing procedures.

These basic tests are an important part of modern day engine troubleshooting and this will not change for some time. Well at least not until the electric vehicle is the only car on the roadways.

The engine runs rough

4 stroke internal combustion engines use compression of the air fuel mixture to maximize the power produced. The upward movement of the piston on the compression stroke will compress the air fuel mixture within the combustion chamber providing an easy to ignite mixture.

An engine with low compression will run rough, and will most likely have a noticeable lack of power.

Not to mention turning on the check engine light due to high engine emissions that will for sure fail the emission tests that are required in most states.

Compression Tester

A compression gauge is used to check the cylinders ability to seal against high pressures. This is an easy to use inexpensive tool that comes with instructions on how to use it.

Before conducting a compression test, it is recommended to disable the ignition and also the fuel system.

You should also find a good and reliable way to hold open the throttle plates.

Even better would be the wide open throttle position to allow the maximum amount of air to enter the cylinder during the compression test.

Why engines run rough?

In a perfect world each cylinder of an internal combustion engine will produce the same amount of vacuum. This is why when you are diagnosing the engine runs rough condition a quick vacuum test is recommended.

Vacuum Tester

When you perform this test the vacuum gauge readings should be steady and give a reading of about 20 inches of mercury.

You can check your auto repair manual for your exact specification which may vary slightly due to compression ratio of your specific engine.

If one cylinder sucks less than the others the needle of the vacuum gauge tester will fluctuate.

When vacuum tests are used on engines that are misfiring, the intensity of the fluctuation of the needle on the vacuum gauge indicates the severity of the mechanical engine problem.

Wild fluctuations may indicate a problem on multiple cylinders. Steady slow fluctuations usually mean a problem on one cylinder.

If the vacuum tester reads low all the time let’s say a reading of 10 inches and is steady as a rock, this could be a sign of a clogged exhaust system. A common car problem that would cause these types of readings is a catalytic convertor problem.

The honey comb catalyst can become damaged and break up and turn sideways severely restricting exhaust flow. If the engine does not breathe well on both inhale (intake) and exhale (exhaust) severe engine health problems may result.

When your engine runs rough it’s hard to enjoy the ride. But also your fuel consumption may increase at the same time your losing power. The exact opposite of what we all expect from our automobiles.

Find out more about the basics of engine operation and how this knowledge can help you diagnose car problems. As well as common tests used by professional mechanics. Discover the You Fix Cars website and my page about rough engine idle.

Or head on back to the main page and look through recent posts on the auto repair information blog.