We are independent & ad-supported. We may earn a commission for purchases made through our links.

Advertiser Disclosure

Our website is an independent, advertising-supported platform. We provide our content free of charge to our readers, and to keep it that way, we rely on revenue generated through advertisements and affiliate partnerships. This means that when you click on certain links on our site and make a purchase, we may earn a commission. Learn more.

How We Make Money

We sustain our operations through affiliate commissions and advertising. If you click on an affiliate link and make a purchase, we may receive a commission from the merchant at no additional cost to you. We also display advertisements on our website, which help generate revenue to support our work and keep our content free for readers. Our editorial team operates independently from our advertising and affiliate partnerships to ensure that our content remains unbiased and focused on providing you with the best information and recommendations based on thorough research and honest evaluations. To remain transparent, we’ve provided a list of our current affiliate partners here.

What is Pre-Ignition?

By Lori Kilchermann
Updated Feb 27, 2024
Our promise to you
WikiMotors is dedicated to creating trustworthy, high-quality content that always prioritizes transparency, integrity, and inclusivity above all else. Our ensure that our content creation and review process includes rigorous fact-checking, evidence-based, and continual updates to ensure accuracy and reliability.

Our Promise to you

Founded in 2002, our company has been a trusted resource for readers seeking informative and engaging content. Our dedication to quality remains unwavering—and will never change. We follow a strict editorial policy, ensuring that our content is authored by highly qualified professionals and edited by subject matter experts. This guarantees that everything we publish is objective, accurate, and trustworthy.

Over the years, we've refined our approach to cover a wide range of topics, providing readers with reliable and practical advice to enhance their knowledge and skills. That's why millions of readers turn to us each year. Join us in celebrating the joy of learning, guided by standards you can trust.

Editorial Standards

At WikiMotors, we are committed to creating content that you can trust. Our editorial process is designed to ensure that every piece of content we publish is accurate, reliable, and informative.

Our team of experienced writers and editors follows a strict set of guidelines to ensure the highest quality content. We conduct thorough research, fact-check all information, and rely on credible sources to back up our claims. Our content is reviewed by subject matter experts to ensure accuracy and clarity.

We believe in transparency and maintain editorial independence from our advertisers. Our team does not receive direct compensation from advertisers, allowing us to create unbiased content that prioritizes your interests.

Pre-ignition happens when the air and fuel mixture in the cylinder of an engine is ignited before the spark plug fires. This is typically caused from a hot spot in the compression chamber or by a spark plug that is too hot. Often called dieseling, the engine can run on after the key is turned off and if allowed to continue, can cause catastrophic engine failure.

Many high-compression racing engines suffer from pre-ignition. The fuel enters the engine and is ignited early by the heat generated from the ultra-high compression pressures, much like a diesel engine. This often causes the engine to break pistons or bend connecting rods as the other cylinders attempt to fire in the correct timing sequence. The best-case scenario will result in engine knocking or pinging.

In some early engines, this run-on was due to excess fuel being drawn into the engine by poorly functioning carburetors after the ignition was turned off. The engine would continue to stutter and pop as the raw fuel entered the hot combustion chamber and pre-ignition occurred. The advent of fuel injection has all but stopped this type of engine behavior.

Pre-ignition as well as engine knock both drastically increase the temperature within the combustion chamber. This virtually ensures that the occurrence of one of these conditions will bring on the other. Pre-ignition results in poor engine performance and is often accompanied by a rough running engine.

The pre-ignition problem is often easy to correct and can be eliminated with minimal effort. Changing to a cooler operating spark plug can often cure pre-ignition in an engine. Proper adjustment of the carburetor and a corrected air-fuel mixture can also cure most pre-ignition conditions. Another cure for the problem can be the addition of a cleaning agent to the vehicle's fuel supply. Also, cleaning the combustion chambers of carbon deposits will often solve the problem.

The timing sequence of combustion in a piston engine is an exact science. Any combustion occurring either too early or too late can cause sever problems. The fuel-air mixture entering the engine must be allowed to travel to its intended destination before igniting. Any variance of this timed event can result in engine damage or destruction.

Engine builders often spend many hours removing sharp edges from engine components. This is done not only to reduce stress risers and prevent parts breakage, but also to prevent hot spots that can cause pre-ignition. By removing the sharp edges with sand paper or other methods, the builder can continue assembling the engine with less fear of problems later on.

WikiMotors is dedicated to providing accurate and trustworthy information. We carefully select reputable sources and employ a rigorous fact-checking process to maintain the highest standards. To learn more about our commitment to accuracy, read our editorial process.

Discussion Comments

By anon957264 — On Jun 19, 2014

I have an Opel Corsa Essentia 1.4 16 valve car. It had a blown gasket which was fixed and the timing is done to spec, but when I start the engine and then switch it off, it takes a couple of seconds to go off, which you call pre-ignition, so what should I do?

WikiMotors, in your inbox

Our latest articles, guides, and more, delivered daily.

WikiMotors, in your inbox

Our latest articles, guides, and more, delivered daily.