Fixing an engine knock can be an intermediate to advanced project for most DIYers. Here’s what you need to know to investigate engine knocking at home.
- DIY Difficulty Level: Medium to Advanced
- Time Required: One or more hours, depending on circumstances
- Tools & Materials:
- Carbon-cleaning additive
- Oil and filter
- Spark plugs
- Spark plug wires
What Is Engine Knocking?
Knocking or pinging noises coming from the engine vary in source and severity. Analyzing the symptoms to determine possible causes is the first step. The issue could be a minor fix or require extensive work. It’s always wise to check on issues before they lead to a breakdown or more serious issues down the road.
Today’s modern vehicles have computerized systems that regulate the fuel and air mixture and many other systems, so engine knock should be uncommon. When the computer can’t fix the problem, the check engine light will illuminate. Older vehicles, especially those with carburetors and ignition points, or that require the engine timing to be set manually, are more susceptible to fuel mix issues that lead to pinging and knocking.
For more information on “What Is Engine Knocking and What Causes It?” and more, check out the Fixdapp blog.
Is It Safe to Drive With a Knocking Engine?
Knocking or pinging noises are indicators that something isn’t working correctly inside your engine. Ignoring an issue can lead to a more serious engine trouble, so any unusual noises need to be checked.
When To Fix a Knocking Engine
Due to the potential severity of internal mechanical issues in your engine, the issue should be diagnosed and repaired as soon as possible. Immediate checks like making sure engine oil and coolant levels are sufficient should be made before driving further.
Disclaimer: The guidelines in this story are general and not meant to replace instructions for your specific vehicle. Please consult your owner’s manual or repair guide before attempting repairs.
What Are Common Symptoms of Engine Knocking
It’s a good idea to monitor your engine’s regular noises and look for any unusual or loud sounds or leaking of oil, coolant, or other fluids. Noises could vary from tapping, knocking, rattling, and pinging. Causes can be as simple as bad fuel, carbon deposits, or needed adjustments to mechanical issues in the engine.
- Tapping engine noise
- Knocking or pinging with timing issues
- Engine rattling
Keep in Mind
Engines usually make noises that vary depending on how high they’re revving and how much strain they’re experiencing. Low rumbling sounds from the engine are normal. Knocking, tapping, or pinging noises may come and go after starting your car while driving, idling, or continuing nonstop while running.
Knocking issues have many possible causes:
- Low-octane fuels burn faster than they should, causing detonation knock. Make sure you always use the correct octane fuel that the manufacturer recommends for your particular engine.
- Incorrect, faulty, or improperly gapped spark plugs cause detonation issues. Narrow gaps cause weak sparks, wide gaps may prevent sparks, and dirty or worn plugs won’t fire correctly.
- A faulty knock sensor won’t relay information to the Engine Control Unit (ECU), which controls fuel injectors, fuel-air mixture, and timing.
- Too lean of an air/fuel mixture, which means too little fuel in the combustion chamber, can cause multiple detonations and knocking. Oxygen and mass air flow sensors, fuel injectors, and fuel pumps could be culprits.
- Carbon build-up inside engine cylinders increases the pressure or creates hot spots, causing premature detonation.
- Low oil levels, old oil, and low oil pressure can lead to an inadequately lubricated cylinder head. This can lead to issues including damaged piston rings, residue on cylinder walls, and compromised performance. Bluish-black smoke indicates oil being burned.
- A valve near the cylinder head closes completely, causing issues regulating air and fuel. Faulty valve lifters may make a clicking or tapping noise, leading to further damage.
- Worn engine bearings or a damaged or broken crankshaft could cause engine noise. Both issues require extensive repairs.
How To Fix Engine Knocking
Step 1: Check oil and coolant levels
Regular oil changes and monitoring fluid levels can prevent significant issues like engine wear and poorly performing timing-related components in the upper portion of the engine. Make sure fluid levels are correct, and that there aren’t any noticeable leaks around the engine or puddles under your vehicle. If you detect an oil issue or an oil change is past due, complete an oil change with high-quality oil and a filter that exceeds the specifications for your vehicle. Fresh oil can prove to remedy engine noise.
Step 2: Upgrade to high-octane fuels
Minor pinging issues could be caused by low-quality or low-octane fuel that causes premature detonation. Fuel and additives with carbon-cleaning properties can help eliminate excess carbon, another potential cause of pinging and knocking.
If your manufacturer specifies mid-grade or premium fuel for your engine, always use it, despite the higher price. While using low-grade fuel may save a little money in the short term, it can cause big engine problems later that will cost much more to fix than using high-grade fuel.
Step 3: Tune up your engine
A tune-up, including new spark plugs and wires, can help fix pinging and knocking caused by loose wires or faulty spark plugs that could be fouled or cracked. You can test your spark plugs to diagnose whether you need to replace them or not. Depending on your situation, you may be able to complete the tune-up yourself. Check to see if your engine has been tuned up in the last couple of years. Spark plugs often last about 100,000 miles, so higher mileage engines likely are due for tuning.
Step 4: Check for more complicated issues
Crankshaft issues or worn-out engine bearings could also cause knocking and require specialized knowledge to diagnose and determine how and if the engine should be repaired. Older or high-mileage cars may not be worth extensive repairs that could cost hundreds or thousands of dollars. Engines with internal mechanical issues likely won’t operate for very long. At this point, some drivers may decide to sell their cars, have repairs made, get a new engine, or have a used engine installed.
Still Need Help?
Do you want an expert mechanic on speed dial who can walk you through DIY repairs and answer any questions you may have regarding your knocking engine and more? Join FIXD Mechanic Hotline for unlimited access to our Master Mechanics Monday-Friday, 8 a.m. to 8 p.m.
At FIXD, our mission is to make car ownership as simple, easy, and affordable as possible. Our research team utilizes the latest automotive data and insights to create tools and resources that help drivers get peace of mind and save money over the life of their car.