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Easy PEASY M50 ICV (Idle Control Valve) cleaning

44480 Views 17 Replies 4 Participants Last post by  EyeDoc1
How happy art thou if thou dost not have an M50 engine. If thou hast an M20, M30 or M60 engine, how happy art thou ! Thy ICV is within easy access, can be removed AND replaced within 3 minutes (with a little practise), and without damaging anything in the process, and on a hot engine without any risk of burns, to boot.

An ICV that is removed can be nicely cleaned out within 5 minutes, with just carburetor cleaner, contact cleaner, brakleen, ethanol, gasoline, or any other organic solvent, sprayed in and shaken in a wrist twisting motion back and forth for 2 minutes, drained out, then hit with a little WD40 to lubricate the valve inside, shaken out, drained out, and then reinstalled and reconnected with all hoses tightened securely. And its clean !!

With an M50 engine, thou must transform into that wisest of all of God's creatures, the serpent, snake one's arm under the intake manifold and throttle body, nudge out the ICV's connector, then the ICV from under its securing plate, lean over and grunt, with the horror of working with a hot engine, and....and...I can't continue it is too awful.

Enter Roberto. A beautiful way to clean the M50's ICV has been created. A beautiful way indeed. Quick, simple effective and takes around 10-15 minutes.

I can't see what I'm typing. Please give me a moment to dry my eyes, and sigh.


M50 ICV cleaning (on-engine)

Look at the big curved intake boot connected to the throttle body. It has a big hose on its bottom right (roughly directly under the tps) that snakes under the intake manifold. This hose connects to the one of the ICV's two ports (the other hose looks like a question mark and connects to the intake manifold from directly behind the throttle body).

This hose is the key to this method.

Here are the steps.

1. Run the engine at idle.
2. Pull the FP fuse while the engine is running and let it die.
3. Try to start the engine for 5 seconds after that. Stop when the engine cannot start. The rail is depressurised now.
4. Yank the hose mentioned earlier from the air intake boot.
5. Hit it with a 10 second burst of carburetor cleaner. It will pool inside and coat the ICV valve with itself.
6. Use your mouth and blow into the hose to ensure the pooled carb cleaner goes all the way into the icv. Leave the hose angled upwards.
7. Get into the car. Switch to key2. Come out and blow into the hose once again to recoat the icv in the on position. Leave the hose angled upwards and get back into the car.

8. Switch between Key0 and Key2 30 times slowly but without pausing in between switches. Key2 switches the ICV on and activates its internal valve and spins it one way. Key0 deactivates it and spins it the other way. Thus you get a total of 30 cycles or 60 spins with this method.

9. Angle the hose downwards. The excess carb cleaner should flow out, and it should be black. That's how you know you have got a good clean out of this.
10. Key2 the ignition and blow deeply and strongly into the hose with your mouth. Then angle the hose back down again as best as you can and let more fluid flow out.
11. Hit the hose inside with a 2 second burst of WD40. Blow hard.
12. Reconnect the hose. Make sure its secure.

[If it goes in too easily, wrap some pipe/pvc tape around it first. Use your fingers to check the hole the hose fits into for cracks. Use high temp silicone non gasket sealant, or replace the boot entirely, if cracks are found or suspected. ]

13. Remove the main relay or unplug the DME. We need to kill spark.
14. Key0 and Key2 the ignition 10 times to let the WD40 coat the ICV's internal valve good.
15. Ventilate the chambers for 10 seconds. This will purge most of the carb cleaner fumes from the intake manifold.

[ Combustion chambers are ventilated by depressurising the fuel rail, holding the throttle wide open, and cranking the engine fast twice in 5 second bursts with a 5 second interval in between ]

16. Reinstall the main relay.
17. Attempt to start the engine. If it starts, let it die naturally.
18. Reinstall the FP fuse.
19. Prime the fuel rail (i.e key2 the ignition for 3 seconds), then start the engine.
20. Let it run, and feather the throttle for a few seconds if need be.
21. After the idle has stabilised, flick the throttle several times. Confirm normal behaviour. The tach needle should quickly but gently settle to its normal idle rpm (this depends on engine temperature) without bouncing down and up to it.

There might be black smoke out the tailpipe for 30-60 seconds. That's fine. Let it play out. Any excess carb cleaner and wd40 will vent out naturally.

I know that looks like a long series of actions - 21 steps. However, when you are smooth with it, it takes under 15 minutes end to end. You don't need to remove the icv and reinstall it. You get it almost as clean as you would if you cleaned it manually. And it can be done easily, every 6-12 months, as part of your DIY maintenance regime, or as part of your DIY troubleshooting sequence if you have potential ICV issues.

If you fail to vent the chambers with the ignition system disabled, you will get a very strong loud scary smokey backfire when you first crank the engine. Unless you think this is way cool, depressurise the rail, disable the ignition system, and vent the chambers first.

Or just follow these 22 steps religiously. If you understand what you're doing conceptually, it won't be a chore. If not just print out and follow the steps without fail.


The ICV gets dirty because it is also exposed to and coated with alot of oil vapour-laden air from the CCV system. The valve inside is made of metal, which gets hotter, and causes sludge to form on it more easily when the engine is shut down. As this sludge builds up (over 6-12 months), it interferes with the smooth oscillation of the internal ICV valve. This manifests as an imperfect idle, and can sometimes be a pretty rough idle and other ICV symptomes such as a bouncing idle, jerky throttle flicks, etc.


Everyone with an M50 engine is invited to try this and to improve on the above listed steps in any significant way.

After you have finished sighing with profound joy, that is.

It is such a simple method that even a noob can do this without much difficulty and without turning it into a skill of some sort, and without any significant safety risk.

And no, there is not even the slightest risk of hydro locking etc if you follow all the steps in the correct sequence. Blow a lot of air through the hose after draining it down. Or you can do this on a hot engine, which causes carb cleaner to vapourise more quickly, if you are really concerned.

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