How to Clean Intake Valves with STP
STP Pro-Series Intake Valve Cleaner lets DIYers get professional grade results in their own garage. This cleaner is designed to remove hardened deposits without any need for an engine teardown (Which can be pricey!). One person can follow 5 steps to clean their intake valves in 20-30 minutes.
The act of exploding the air-fuel mixture can lead to the development hardened deposits within the intake valves of internal combustion engines. These deposits are troublesome, because they can cause detonation, disrupt the atomization of air-fuel mixture, and potentially keep the valve slightly open, which will reduce the compression of individual cylinders. Problems like these can lower fuel economy and cause rough idling or sluggish acceleration.
See the process below. To get started, you'll need a screwdriver, safety glasses, and gloves.
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How to Use STP Intake Valve Cleaner
Safety and Prep
Wear protective gloves and eyewear throughout these steps.
Park in a well-ventilated area, start your engine, idle for 5 minutes, and write down the engine's idle speed before shutting the car off.
Once the engine's off, pop the hood and locate your vehicle's throttle body. Look after the engine air filter and boot connection on the engine side. Use your screwdriver to loosen the clamp that holds the intake boot, and pull back the top of the boot slightly.
Ready the Can
Shake the can gently, uncoil the hose, and hang the intake cleaner can above the throttle body or on the hook for the hood latch. Make sure that the hose is clear of belts, fans, or any other moving parts, and that the can is away from any sources of extreme heat.
After positioning the can, insert the hose end towards the throttle plate, keeping the hose in place on the throttle body with the protective aluminum guide. Then reattach the air intake boot back on the throttle body and create a tight seal.
NOTE: Do not feed the hose into the Mass Air Flow (MAF) Sensor.
Dispense the Formula and Rev
Turn the red dial all the way to "I" and then turn the blue switch to the "I" position. The dial must terminate at "I" to ensure proper function.
Start the engine within 1 minute and the cleaning formula will begin to dispense in about 1 minute. Rev the engine to increase it to around 3x factory idle speed. Some vehicles will not allow you to rev the engine at 3x idle speed. If so, rev as high as the engine will let you (usually 2000 RPM).
NOTE: You might need to feather the gas pedal during cleaning to maintain proper idle. If your car has sophisticated electronics, the Check Engine Light (CEL) could come on. Most of the time, this will correct itself after cleaning is over.
Maintain 3x Idle Speed
Keep the engine at 3x factory idle speed for 9 minutes while the cleaning formula goes through the intake system. Turn off the engine after 9 minutes.
Putting it All Back Together
With the engine off, turn the blue switch back to "O" to shut off, and then loosen the air intake boot just enough to remove the hose and guide from the throttle body.
After removing the hose and guide, reattach and reclamp the intake boot. After cleaning, drive for 10-15 minutes to ensure the formula exhausts from the intake system, removing any remaining carbon build-up. If the CEL came on while cleaning, it should clear while you are driving it for 10-15 minutes.
STP’s Intake Valve Cleaner works in GDI, PFI, and turbocharged engines, and it is designed to be used once a year or every 12,000 miles.