Tech Tip - January 2009

Carter Automotive
107 West 11th Street
Coffeyville, KS 67337
Phone: (800) 225-4813 (620) 251-4700
FAX: (620) 251-2215

Four most common causes of engine "pinging".

Pinging, knocking and detonation are all terms for a condition known as "pre-ignition". That means some of the gas and air mixture is igniting in the cylinder before it's supposed to. And when that extra flame front crashes into the normal flame front (created by the spark plug), you hear a noise, and that noise is pinging.

There are four major causes of pinging. The first three are related to heat.

Overheating: The first is severe engine overheating. If the engine is running too hot for any reason, the temperature in the cylinders can simply be too high. In that case, some of the mixture can ignite before the spark plug fires just from the intense heat.

Overheating can occur for several reasons. The coolant level inside the radiator may be too low. The thermostat may be stuck partially closed. The flow of air through the radiator may be blocked by bugs, road dirt or debris. The fan or shroud may be damaged. The fan belt may be slipping. The fan clutch may be slipping.

Identifying the root cause of engine overheating is important not only to eliminate pinging, but also for extending the life of your vehicle's engine.

Carbon buildup: The second major cause of pinging is carbon buildup inside the cylinders and on the pistons.

Carbon builds up inside the engine's intake chamber and around valves slowly. Often, the process occurs when the engine is shut off and a small amount of liquid gas is left in the intake area from the last firing of each fuel injector. The liquid gasoline quickly vaporizes on the hot metal of the engine leaving behind a small amount of residue. Over time, especially in an engine that does many short trips and is turned off and on a lot, the carbon builds up to levels which can affect the smooth flow of air and fuel into the engine.

When too much carbon collects around the valves, it can lead to drips of gasoline entering the combustion area instead of fully vaporized gas and air. When the carbon collects inside the cylinder itself, it can reduce the size of the cylinders (increasing the compression and temperature of the cylinder contents) and retain excessive heat. The carbon acts as an insulating layer preventing efficient heat transfer away from the cylinder wall to the circulating coolant.

Carbon buildup can be removed by using throttle body cleaner or seafoam or injector cleaner type products. Fogging products are also available that are sprayed into the engine intake and allowed to settle and loosen carbon. In severe cases, the spark plugs might need to be replaced after cleaning the carbon.

EGR Valve: The third cause of pinging is a malfunctioning exhaust gas recirculation (EGR) system. The EGR is supposed to send non-combustible exhaust gas into the cylinders to lower the temperature of the mixture.

How does 800-degree exhaust gas LOWER the temperature in the cylinders? Because it doesn't burn, and it crowds out some of the oxygen that would have burned and made an even hotter flame. And if that EGR is not working properly, the cylinder temperature can be too hot and the engine can ping.

Faulty EGR valves can sometimes be cleaned. If it is not repairable, it should be replaced.

Timing: And finally, incorrect ignition timing can cause pinging. The ignition timing determines when the spark plugs fire. And if they're set to fire too early, the stuff will begin to burn too early.

Modern engines use a variety of sensors to correctly adjust the engine timing "on the go" for best power and fuel economy. These include crank position sensors, drive by wire throttle systems, pre-ignition detectors, individual coil packs, and spark advance modules that all work with the ECM or brain of your engine to adjust it to pre-determined settings mapped out by the engineers who designed the engine.

These systems are designed to keep your engine operating within safe limits that protect it from damaging itself. When one of the sensors or control units malfunction, it should throw a code and set the check engine light alerting the driver that something is wrong.

The use of higher-octane gas often makes the pinging stop because it has a higher ignition point. By requiring a higher temperature to make the gasoline burn, you reduce the likelihood of it "pre-igniting" somewhere else in the cylinder.

But premium gas doesn't address the underlying problem. So start by checking the EGR system, the cooling system and the ignition timing. If your check engine light is on, bring it in to Carters so they can read the code(s) with their scanner and identify the broken component.

And if none of those things fix it, then you can consider using a higher-octane fuel.

We hope these reminders will help you to keep your car or truck running smoothly all year round with no surprises. If you are unsure about how to do something, the friendly service team at Carter Automotive will be glad to help. Carters stocks a full line of chemicals, coolants, and replacement parts to help keep your engine running smoothly and efficiently and to help you protect your automotive investment.

Print me and take me to one of the 6 Carter Automotive locations in SE Kansas. Our friendly and knowledgeable counter staff will help you find the perfect parts for your application at the right price.