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Easy PEASY M50 ICV (Idle Control Valve) cleaning

43372 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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Given the religious nature of this post...from Denmark no less...

I was thinking of printing this out and putting 1 copy in my Bentley manual, and 1 copy is a Bible. I knoweth the snake arm method for that little ribbed hose that bends at a 90 degree angle and constantly falls off IF you don't have the little plastic hooter (sorry, don't know the exact name of that part), but the hooter has a little FLANGE that holds the hose tight. Problem is, this is often broken off and nobody knows it, and just jams the hose on, thinking it'll hold. WRONG, as I know, from having to jam the hose back on when it's blown off (and the motor is hot-hence references to Satan and snakes). THANKS BIG TIME for this right up. Very handy and very detailed.

The Lord will stuff a few more feathers in your pillow for your good works.


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And, given I've got this problem now...

Will be trying this this weekend. Unless anyone else has a super suggestion about cleaning ICV's without dissassemblying the manifold.
I actually performed the trick as suggested by our friend from Australia

It did not take that long...however, having a spare piece of hose made blowing the carb cleaner and WD-40 a whole lot easier. One thing to be aware of is when you are trying to drain the hose in a downward position toward the ground, you run the risk of disconnecting something else that you really can't see. I have had major major issues with that ribbed 90 degree bend hose coming loose from the manifold, and it's a problem with the broken flange on the small plastic part that keeps the hose connected to the manifold. This part is easily broken when someone starts yanking on components that they can't see (ie, someone changed the starter and broke the part and either didn't know it or just jammed the hose on and hoped for the best. It will eventually disconnect due to pressure and your car will run like a Mack truck with a disconnected cylinder at low speed. Working in the tunnel area is difficult unless you have small arms and hands, and trying to access from under the car is not much of a major improvement.

The part in question is Air Hose Connector with O-Ring - Intake Manifold to Idle Control Valve Hose found on Pelican's website. The flange I mention is the pointy plastic part on the top of the picture. Cost is $10.50 and buy it from them. I'll see if I can attach it.

But the procedure to clean the valve on the 21 point exam, so to speak, was very clear and detailed, and I learned a few thing I didn't know about the car (location of relays and main components). Just take your time especially removing hoses, and you shouldn't have a problem.


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The post was by Mamij...unless he moved to Denmark...

and changed his name.

As for being an arse, well, the last thing this WORLD needs is two Jersey boys arguing over something, without regard that Jersey boys love to argue about anything...201 vs 609, Yankees, Mets...whether the Dodgers should have left Brooklyn or not and the best place for a pizza...and you know, a real pizza, not one of these corporate Frisbees.

The idea behind the 21 point cleaning was it was purported to be FAST and EASY, and I was trying to clear up a rough idle. Anyone with an M50 engine knows the ICV valve is almost impossible to service properly WITHOUT taking off the manifold. I get that. In one of the sentences you wrote, you said it was easy, followed later by two sentences that used the word "difficult". I can do easy, the difficult takes slightly...well, who's kidding who, a whole lot longer. I've pulled manifolds and sometimes, lo and behold, getting them back on and sealing properly tends to make me wish I never started (and lets not talk about breaking a stud removing it from the old '66 Plymouth--in winter, of course)

There are threads about whether you need to remove the manifold to change the starter, and 60 responses to the thread left me with the feeling of..."it depends".

One thing you didn't mention is whether you need a gasket set once you crack open the intake. I assume you do, so there's an additional expense that you may or may not need IF the 21 point cleaning works. The only thing I didn't fully understand was the use of "WD-40", as it's known as "Water Dispersing compound #40". Supposed to displace carb cleaner, which would normally evaporate or burn off, or erroneously thought to be a lubricant, which we all agree it is not. Just look on the can, and you'll not see lubricant. WD-40 made a great lubricant called "TAL-5", but it never made it commercially as a success. I was lucky to have a rep drop off some samples and it was great stuff, but in the same "you lose the red straw" and people just hate you.

I've seen a Roberto post here and there, and it this was his originally, then I get your drift.

I've still got this low grade rough idle which sometimes trips the CEL, and I've changed the MAF, TPS, and tried cleaning the ICV. I've changed the O2 sensor, but used a Denso, figuring that would be just fine, since I've Denso components elsewhere (think AC compressor, when I upgraded the 1991 to 1994 R-134 standards.

The last time EVERYTHING on a car was easily accessible was on the 1959 Ford, whose front hood was hinged in the front. Or, as the recipient of a Medicare card, maybe I'm mistaken.

All thoughts are appreciated, and yes, if I can't fix this, I'll tear down the compartment to remove the manifold to try and find an elusive vacuum leak. It's gotta be something.

Best regards

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Shoot, I remember when people flew to Denmark to have "the operation"

Something for you to Google. One day I'll tell the story of Robert in the spring semester and Roberta in the fall semester at Univ of Texas at San Antonio. See above reference.

Sometimes you're born at the intersection of Rts. 1 & 9, and some times you castigate your parents for NOT buying that bungalow on the causeway to LBI for $2,875.00, guaranteeing those hardy souls flying over the Pulaski Skyway (8th Wonder of the World--no joke) a permanent shore experience for their kids. But noooooo...he just had to buy that '54 Buick.

Now that's a good post and good write up on pulling a manifold, something I haven't tried. Once the manifold is off, anything you think is a "must replace" item, so you don't have to do it again?

My brother still has his Bell Ford '69 Mach 1 in the garage. Bought it with his savings from doing his duty in Vietnam. Faces Detroit each and every morning and kicks himself in the fanny for not buying the CobraJet 428 RamAir model (plus air conditioning). You live, you learn. But that would have set him back more than 4K!

But seriously, great post on the manifold. More detail is always better than less.


PS...1969 Mets. Who'd have thunk it that they'd will the World Series. Now that was truly Amazin'
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Wait a second...Victoria, Courtenay, Comox...I had to Google all that. Since I'm from Vancouver, Washington (also called "Vansterdam" since we now have legal marihuana), on the mighty Columbia River across the border from the People's Republic of Oregon, I'm distressed to find that the Canadians saw fit to rip off our fine name and put it in a dinky place called Vancouver, British Columbia. I have to read the papers once in awhile. Go figure!
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Lemme tell you sumpthin'

Jersey people may be sometimes gullible, and maybe even sometime stoopid, but if you guys vote to go with self service gas, yer all idiots. Two states hung tough...Jersey and Oregon, and I live on the border between the two. WA State gas is routinely 5-8 cents more expensive than Oregon, so I gas up in Oregon as much as I can. I hate pumping gas, but out here in WA, (and every other state that bought into this line of crap) there's more of the...park your car, get out, walk to the convenience store, wait in line, pay the guy, then pump, then go back inside, wait in line AGAIN, and get your change. OR, put nothing larger that a 20 in a kiosk, and if you put in too much, see example above.

I was a gas pumper back in the day, and it was a service (made a nickel a quart of oil as a commission + got to keep anything left over from the days before oil came in screw capped bottles, a Godsend for the '62 Ford with the bad rings (40W, straight worked best)). I thought Christie was out of this fight and Sweeney was against is, so, in one of those rare instances, I go with the Dems on this one. Anyone that says you're gonna save money at the pump is sniffin too much ethyl. For once, "Jrzy Girls Don't Pump Gas" is spot on.

And I throw the guy pumpin' on a cold crappy day a few bucks for coffee. I remember those days as a college kid makin' $1.25/hr honest money. Learned something about cars too.
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Sadly, Satin Dolls in Lodi is no more but...

it's time to revisit this issue of ICV valve cleaning, since my son has custody of said 1991 E34, and I'm hoping to get at least another year before putting the .45 pistol to the engine block like an old Cavalry trooper. I've learned that the words "banned" now show up under a person's name, and its for a reason. Quick question. I'm gonna pull the intake manifold before tackling this job and that engenders the gasket set. Do you need to get new gaskets? If so, I'l have to probably order then before taking a crack at this. Give me your best Jersey opinion please.


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Looks like Satin Dolls has "left the building" in more ways than one.

As soon as I hit the send button, I went up and reread the various posts and realized "of course you change the gaskets, you idiot...the car was built in Munich in Nov of 1990", one month before I got called up from the Army Reserves and shipped out for Desert Storm. My wife at the time was pregnant with the current owner, my son. Yeah, change the gaskets and while you're at it, do some research on other hoses under that intake manifold and replace them while everything is exposed. I drive a '94 E36 with the same motor, so there's some overlap. Like most things with cars, somethings will change out easy, and some will be a bitch and a half. Pretty much the same with virtually everything made that's mechanical. When I read and re-read what you posted, I think things were clear enough for me to follow, and it doesn't look all that daunting to do the job. I just hate doing the job in the winter, as I'm a fair weather part changer. My interest in cars came about when I was going to college in the late '60's and the old '62 Ford wouldn't start, and it was January, the streets were slushy, it was snowing lightly, and I was in dress shoes (we still went to college back then, in Jersey City no less, in coat and tie as fine Christian gentlemen).

I swore that I was going to learn as much about a car as I could so this would never happen again.

Can't say I've never been stranded since '67, but I've had more than a fair shot at fixing something on the road than having my car towed (happened only twice-E34 fuel pump and E34 steering column failure). Now that I think about it, why do I still own this car? Or rather, why did I give it to my son, and still effectively "own this car". Anyway, I appreciate your posting, information and the help you provided. The knowledge gained is and was certainly useful.


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I decided to bite the bullet on taking off the intake manifold, and your information was very helpful. Be mindful, this was a 1991 E34, and not all E34's have the exact same configurations. So take my advice with a grain of salt if your year is different and part of the later run in the series. I plan on doing a write up with pictures, if I can figure out how to upload them, detailing my experience with reaching the ICV. Anyway, I smoked a damned Swisher Sweet (2 for $1.79 plus tax at Safeway) and blew smoke into a vacuum line up by the PCV value and couldn't find a leak... until I started disassembly and then I discovered a split fitting in the 90 degree VERY LARGE "boot" hose (if you can call it that) that was NOT visible unless the boot was loosen from the throttle body and removed...meaning as you were bending over the car from the front driver's fender, from the 6 o'clock viewpoint, the break in the boot was exactly at the 12 o'clock position, meaning, facing the side of the motor and NOT VISIBLE on cursory inspection. It was the larger of the two vacuum hoses, the one that runs to the ICV and is closest to the firewall...about a foot long (the hose in question) and an inch thick. There is a slightly angled plastic "connector" between the boot and the ICV hose, and both my ICV-Boot hose, AND the boot itself we're compromised, meaning cracked at the top. I almost called it quits and declared the problem solved, but couldn't shake the feeling that the ICV value would need attention. So I followed your advice and tore into the intake manifold removal process. I'm going to have to replace a small short rubber fuel hose as the one in the front that attaches to the fuel rail (there are two) pretty much disintegrated. No big issue there. It needed to replaced. And once I got to the ICV and figured how to disconnect the electrical connector (super easy IF YOU REMEMBER to press "IN" on the wire and wiggle it out. My ICV was plugged. No movement was detected upon shaking the ICV unit. With a Harbor Freight orange handled pick, I was able to barely move the innards. However, with about 15 Q-Tips, some brake cleaner, and some elbow grease, I got the valve "unstuck", meaning basically, when you shake it from side to side in a twisting motion, it should rattle. Mine didn't, but it sure does now. I ordered new hoses, air filter, PCV value and other parts from Pelican Parts, so they are arriving tonight, and tomorrow I should have it all buttoned up and test fired. Here's hoping.
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