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A Quick Guide to Degrading Engine Power

Posted by Scott Goldfarb on

If you take your diesel-powered vehicle up a hill regularly and notice one day it doesn't seem to handle it as well as usual, you might rightfully be concerned. A number of factors could contribute to the degrading of your engine's power. Here's a quick guide to help you troubleshoot the reason your engine isn't functioning at its best.

1. Check Engine Light. The first place to check is your check engine light. If the light is illuminated, run some diagnostic software to determine what is causing the issue, or take it to a shop to be checked out. There are many different scenarios that could cause a check engine light to turn on, so using the software codes is an easy way to figure out what is going on under the hood.

2. Dirty Fuel Filter. If there is no check engine light, a common culprit for low power is a dirty fuel filter. Fuel filters are installed to keep water and dirt from entering the fuel, and when they do their job well, they can get clogged up themselves. Although it is tempting to only fix one of the two filters, it is best to change both of them at the same time. If you empty them and find an excessive amount of trash and water, you may want to consider draining the tank.

3. Plugged Exhaust. Unnecessary back pressure can be created when the exhaust system is plugged. This will cause a serious decline in the engine's power. Mufflers need to be replaced occasionally. If you notice condensation, a strange noise, or a bad smell from the engine's exhaust, consult the manufacturer's recommendation for changing the muffler. You may be overdue.

4. Failing Fuel Injectors. A failed fuel injector might turn on the check engine light, but it is not guaranteed to trigger it. Diagnostic software typically has a test for the diesel performance injector. Be sure to test all of the fuel injectors, as more than one can be bad at the same time.

5. Malfunctioning Turbocharger. Any damage to the turbocharger or trash that enters the turbo can cause a loss of power. You can perform a visual inspection on the turbocharger, and if nothing seems out of place, you can run diagnostic tests to see if the turbo or actuator are damaged.

6. Air Intake Problems. If the air intake has a leak or other restriction, the engine is not working as efficiently as it can, and you will easily lose 20% of your engine's power. Start by inspecting the turbo clamps. The clamps will naturally loosen over time due to the vibrations of the engine. Check them against the torque spec to make sure they are where they are recommended to be, but also make sure they are lined up correctly.

If the clamps seem to be correct, check the hoses. Hoses can wear down due to chafing or any friction against them. Pinholes can also develop in the hoses. If the hoses are in good condition, also check the air filter for any obstructions.

7. Throttle Pedal Malfunction. While a throttle pedal malfunction will often trigger the check engine light, it does not always. The throttle position sensor (TPS) can fail in different ways, including having dead areas on the pedal, malfunction of the hardware itself, the pedal not being accurate, and bouncing readings. Diagnostic software can help determine the accuracy of the pedal.

8. Low Fuel Pressure. Since fuel is absolutely necessary to power the diesel engine, it makes sense that a decreased amount of fuel will give you a decreased amount of power. Check the fuel system lines for any leaks or weak and loose spots. If air is able to penetrate the system at any point, it will decrease the power of the engine. The lines can soften over time, and that softening can make them porous and susceptible to airflow.

9. Internal Diesel Engine Problems. If none of the above seem to be the problem with power for your diesel engine, the engine might be experiencing internal problems. This can be anything from a compromised head or head gasket to a damaged diesel camshaft to bad or poorly adjusted diesel delivery valves. If you are able to troubleshoot and eliminate all other options, take your diesel engine to a mechanic for an inspection to help you determine why you are losing power.

As you work your way down the list to find the reason your diesel engine is experiencing a power loss, remember that more than one problem could be presenting itself at the same time. Just because you find a dirty fuel filter and replace it does not mean that there aren't also problems with the air intake system and the engine needs new fuel injectors. If you are having power trouble, take the time to rule out all of these possibilities so you can get to the bottom of it completely and restore your engine to its full power.

If you are in need of any diesel parts while you are maintaining your engine, be sure to check our online inventory. We have parts for every type of diesel engine.


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