ISCV - Idle Speed Control Valve - Servicing

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ISCV - Idle Speed Control Valve - Servicing

Post  2wheelsagain on Thu 16 Apr 2015, 10:50 am

Having B1250 idling problems?
Read on and service and clean the ISCV (Idle Speed Control Valve) yourself.
The ISC is the valve body under the throats of the throttle bodies on the right hand side.
It's what controls your idle speed. You need a torx driver for it.

Option 1;
Unscrew it, disconnect the two hoses running away from it, and run some carb/injector cleaner through the bore to run the cleaner over the piston which protrudes into the bores and let it dry. Cleaned out very back of the inlet with a rod and lint free linen and lots of gunk will probably came out which may be preventing the spring loaded piston from travelling as far into the valve inlet as it should.

Option 2;
Take it to a dealer and be done over by qualified people having a "guess" at whats wrong.

Associated threads HERE and HERE and TWT HERE

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Re: ISCV - Idle Speed Control Valve - Servicing

Post  2wheelsagain on Thu 16 Apr 2015, 10:51 am







Thanks to barry_mcki for the above


Last edited by 2wheelsagain on Fri 17 Apr 2015, 12:52 pm; edited 1 time in total

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Re: ISCV - Idle Speed Control Valve - Servicing

Post  #Tag on Thu 16 Apr 2015, 6:34 pm

Chris, as your going to sticky I'd thought I'd try to write it out in English:

Two members have had recent problems with the idle on their Bandits. One was an occasional drop to 900rpm and the other was a highly erratic idle.
Cleaning of the ISCV cured the problem in these two cases. 

The ISCV is the valve under the throttle body throats on the right hand side. It has 3 vacuum hoses running from it. One draws air from the airbox and the two outgoing feed air back into the throttle bodies. A stepper motor in the valve runs a piston into the air passages to allow more/less air to pass and alter the idle air/fuel mix to give a stable idle.

Before beginning the manual states - if the ISCV is disconnected sooner than 5 seconds after the ignition is turned off a bad position could be written to the ECU which will give an EFI error code on startup and require a reset via SDS/OBD. Neither member required a reset and the ISCV assumed normal operation on restart.

For removal, if your a contortionist you may be able to remove the valve with the throttle bodies slid out the right side but I'd recommend removal of the bodies and get in on the bench. (I only say that because reconnection of the throttle cables drives me to utter distraction and my neighbour gets the shits when I knock on his door for the fourth time to retrieve the throttle bodies after I've flung the bastard thing over the fence into his backyard)

There are three screws securing the valve : 2 x T27 security torx in the valve and a #2 JIS securing a saddle holding the two return lines. The airbox feed tube can stay in place for removal/cleaning. A Phillips can be substituted for the JIS but if you have to knock on your neighbours front door after stripping out the heads it's your problem, not mine.

These screws are like most screws that have been in alloy for a long time and can take quite a bit of force to break out the first time and I'd recommend a dose of penetrant to the head first and if you've got an impact screwdriver get it out - they're great for breaking screws out of alloy for the first time and a dab of antisieze compound on the threads on reassembly is great for the next removal.

Once removed the two air ports through the valve are easily accessed and the piston that controls the airflow is easily seen from one side.
I had the minor stumbling and a good flush with carby cleaner and wait till dry was all I needed but another member had a bigger problem which required removing the piston from the valve for clean out.

As I said before, on reassembly neither of us needed to reset the ISC Learned Value via diagnostic software and normal operation ensued with our idles stable (But you might Twisted Evil )

For the amusement of the reader:
The manual also states "We recommend replacement of the O-rings on the connector tubes at each servicing. But we at Suzuki don't have them on our parts list. So we recommend you buy a new ISCV from us each time you service the ISCV"
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Re: ISCV - Idle Speed Control Valve - Servicing

Post  paul on Thu 16 Apr 2015, 7:04 pm

And so there is no confusion , it is the black plastic thing and the metal part it is connected to which I'm pointing at, it's on the right hand side of the bike under the throttle bodies 


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Re: ISCV - Idle Speed Control Valve - Servicing

Post  ScottG on Thu 16 Apr 2015, 9:45 pm

Points to note regarding above;

1. It is not necessary to remove the throttle bodies in order to remove the ISC solenoid and piston. The piston is a little plastic cylinder that is sprung loaded on the solenoid arm.

2. To check it is working you can have it functioning outside of the air intake in which it sits - turn on the ignition key but DO NOT START the engine. Upon turning it on and off you will see the valve reset itself, *listen to what it sounds like* and make sure it sounds same when reinstalled in the air intake bore where it sits.

3. It is the DISTANCE on preset of the small plastic cylinder inside the air intake bore that affects the idle. When it is nearly all the way in at the very last 1-1.5mm you need to push it in because it will spring back, this distance is what hugely affects the rate of idle and if there is buildup at the back of the air intake then the little plastic cylinder cannot enter all the way in and will be a wrong preset and expose air instead of blocking it.

If anyone has same problem and needs help let us know as I spent quite some time and frustration on the issue. Nothing as frustrating as not being able the ride and not know what problem is but very satisfying once you nail it.

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Re: ISCV - Idle Speed Control Valve - Servicing

Post  #Tag on Thu 16 Apr 2015, 10:26 pm

Whoa! Flash! Revelation!  (Hey, Chris, can we have a light going on emoticon?)

I automatically removed the whole valve because that's how the manual said to do it.

You hadn't said before you were just removing the two screws in the electrical housing and pulling the connector, motor and piston out of the valve while it remained in place (that's right isn't it?) 

That's way less work than the recommended method. You should have been giving me instructions.


Last edited by #Tag on Fri 17 Apr 2015, 3:44 pm; edited 1 time in total
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Re: ISCV - Idle Speed Control Valve - Servicing

Post  2wheelsagain on Fri 17 Apr 2015, 7:02 am

All the above is exactly what I was wanting.  Good contributions lads. Thanks.

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Re: ISCV - Idle Speed Control Valve - Servicing

Post  #Tag on Fri 17 Apr 2015, 3:48 pm

This thread is starting to look like a bought one, Chris

Onya, Barry. Paul is quick but you bring quality. 
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Re: ISCV - Idle Speed Control Valve - Servicing

Post  ScottG on Fri 17 Apr 2015, 4:57 pm

#Tag wrote:
You hadn't said before you were just removing the two screws in the electrical housing and pulling the connector, motor and piston out of the valve while it remained in place (that's right isn't it?) 

Yes, that's right. all you need to do is undo the two torx t screws, leave the housing in place and then remove the solenoid unit with the piston attached and pull it pretty well straight out without twisting it because the plastic cylinder is held in place or locked by pushing down on the spring and twisting it where an end "T" shaped piece on the end of the solenoid arm locks it into position.

And it will operate completely outside of the housing so you can check if it is malfunctioning but obviously only turn the bike on and off - don't start the engine.

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Re: ISCV - Idle Speed Control Valve - Servicing

Post  paul on Fri 17 Apr 2015, 6:45 pm

#Tag wrote:This thread is starting to look like a bought one, Chris

Onya, Barry. Paul is quick but you bring quality. 
What ..........so you don't think my finger is classy ? Laughing (Damn and that's my very best one as well  Sad )

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Re: ISCV - Idle Speed Control Valve - Servicing

Post  Ad on Mon 14 Sep 2015, 8:00 pm

I will be trying this tomorrow but have a question about the sounds of this component.    It has all the tell tale signs of bad idle but smooth running so i assume this is the issue as fuel pump is replaced and everything else is serviced and in order.   

I have never noticed any noise from the ISCV after shutting ignition off but now its makes what could be best explained is a lazy ticking noise.
Does this tell me that it is full of crapola and needs a clean out?
I priced these units today at a cost of $265 plus fitting.   Question

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Re: ISCV - Idle Speed Control Valve - Servicing

Post  #Tag on Tue 15 Sep 2015, 10:07 am

The screws that hold the valve in are Security Torx 25 (the screws that hold the valve housing to the throttle bodies are T27). If there is grunge/corrosion in the head it will seem tight - I have to lightly tap the driver into the head with a hammer to ensure it seats well and doesn't strip. A T20 is too small.

It may not be the cause of your problem but it takes ten minutes and it's free (well, it is if you have a T25 driver and some carby cleaner in the shed)
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Had a win.

Post  bigboresuzuki on Mon 09 Apr 2018, 6:31 pm

Bloody Brilliant this Forum. Took my ISC Valve out on the weekend as my idling was all over the place and had lost acceleration too.( Put a new fuel pump in the week before.)  Changed the Torx screws to allen head ones whilst at it.
 Put her back together and Voila...off she went like a cat on acid...or is that a hot tin roof. Anyway, thanks for the input guys as it beats going to a service centre.  Mark.
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Re: ISCV - Idle Speed Control Valve - Servicing

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