Halderman: What you are hearing is called one of several terms used in the industry including:
• Ping
• Detonation
• Spark knock (my favorite term for this)
The cause is the uneven burning of the air-fuel mixture inside the cylinders of the engine. Engineers have said that if you hear a little spark knock, that means that the engine is tuned for maximum power. Sometimes this is called “the sound of economy” because if you do not hear it the engine could be adjusted to give slightly more power and better fuel economy. However, if this noise is just now being heard and it was not heard before, something has changed to make this occur. Several possible causes include:
1. A tank of fuel that has a lower octane rating compared to the fuel you had been using
2. A restricted exhaust gas recirculation valve or passages, limiting the amount of exhaust gases being re-circulated back into the combustion chamber.
3. Carbon buildup inside the combustion chamber
Therefore, the first thing you can do is to try a different brand of gasoline. You should not have to purchase midgrade (plus) or premium fuel, although this will stop the noise, but will not solve the root cause and will cost more. If this action does not help, try using Techron in the gas tank. Techron is the only gasoline additive I know that is approved by several vehicle manufacturers. If after using Techron for a tank and the problem is still present, then it is time to see a professional service technician.
A service technician can check the computer using a scan tool to see if there is any indication of faults with the EGR system or some other problem, such as with the cooling system that can cause the engine to operate hotter than normal. Often a cleaning of the exhaust passages around the EGR valve will solve this problem but only after the engine control system has been checked and confirmed to be operating correctly.
James D. Halderman is an ASE-certified master technician, a member of the Society of Automotive Engineers and the author of 12 textbooks. Submit your automotive care questions to Halderman via e-mail at jhalderman2@juno.com, or write him in care of: Wheels, Marketing Publications Department, Dayton Daily News, 1611 S. Main St., Dayton OH 45409.
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