3 tips to keep direct injection clean

Valve gunk is nasty stuff that comes from the toxic vapour of steam, oil, gasoline and hydrocarbons circulating around the inside of your engine.

It’s a normal process of combustion in any gasoline powerplant and, normally, gunk-causing vapour is vented back into your vehicle’s intake system, where it’s sucked into the cylinders and burned up.

En route to the cylinders, that nasty vapour or ‘blow-by’ passes the intake valves, where it can leave deposits behind. These deposits accumulate, harden, and turn into valve gunk. What cholesterol is to humans, valve gunk is to an engine — over time, it can build up and cause issues with the heart of your ride.

Lately, more and more reports of gunk-related issues are surfacing on owner forums relating to vehicles powered by direct injected (DI) engines. What’s the issue?

In an older engine with conventional ‘port injection,’ fuel injectors sit above the intake valves. When these injectors squirt their fuel into the cylinder, that fuel washes the tops of the intake valves clean.

It’s a process that happens many, many times per second, whenever the engine is running. In effect, the gunk-causing deposits are cleaned off of the valves in real time, as quickly as they’re deposited there, and burned off in the cylinder below. But the new breed of direct injected, or turbocharged direct injected engines, have fuel injectors directly inside the cylinders — not outside, and above the intake valves.

Only air and gunk-causing vapour goes past the intake valves in a direct injected engine. There’s no repetitive pressurized squirting of gasoline over the intake valves to help keep them clean.

So, same oily blow-by, same potential for deposits, but no cleansing spray of fuel over the valves. This can allow valve gunk to build up, unchecked, and quickly.

There’s more. If valve gunk deposits build up enough to cause problems in a direct injection engine (including a loss of compression, poor fuel mileage, even possible engine damage), the commonly-accepted fix is to partially dismantle the engine and clean it manually. This is not inexpensive.

Thankfully, following three simple tips can help fend off the build-up of valve gunk in this increasingly popular style of engine. If you’re not running a direct injection engine in your current ride, chances are, you will in your next one. If that’s the case, be sure to bear the following in mind to minimize or eliminate valve gunk buildup, to ensure long and trouble-free engine life. Follow your factory-prescribed spark-plug change intervals religiously, every single time and consider changing them early, too. Reason? As your spark plugs age, they wear out, reducing the effectiveness and efficiency of the combustion process. Running older plugs, and especially, plugs past their service life, quickly diminishes the cleanliness of the combustion process, causing your engine to generate more contaminants and soot, which contribute to valve gunk indirectly.

Worst of all, old plugs can strain your ignition coil packs, which may cause them to overheat and suffer damage while trying to fire an old plug.