Hello allNew to the forum.
I bought a used 2010 king quad 500axi recently.
It runs, but not well.
did not start every time. Acts like a cold carburator engine.
The idle at rest fluctuates up and down, if in neutralIf it's in gear, the machine with lurch forward.
When going into gear, it grinds a bit, then goes in. (Idle too fast?)
When I get it running and increase the throttle then release, it does not return to minimum idle very fast. Stays at an increased level... Then returns to the up and down.

I started searching...
Jumper on the plug under the seat and the code is -C40. The- (dash) is in the middle. ( Proper TPS) The red FI might is on solid as well.
that lead me to the idle control sensor.
Replaced, no change.
More research, the wires that connect the ICS to the ECU. I used my multimeter to check continuity and shorts to ground or supply voltage. All good.( Battery disconnected)

I checked for 12v supply at the ICS plug, good.
Brand new battery that is meant to be used on an ATV.
Voltage measure ~14v while running and just over 13v when not running. 12.8v when not running and headlights on. These measurements seem normal.

I started the engine with the ISC plug remove and the idle is exactly the same. (?)

New spark plugs and Chevron injector cleaner, seafoam as well...

I can't figure it out...
Any help will be very appreciated.
I don't have a big ego, so If you see anything boneheaded that I've done, let me know.

Jarrett Liner

 

I took the air box off and the intake is exposed.
The idle control sensor is right there( of course). I'm pretty sure the ICS adds or restricts the air coming in when the throttle is closed and The engine is set to idle.
So when the idle is going up and down, I put my finger over the hole inside the intake where the ICS is supposed to add or restrict the air flow.
When I covered the hole, the idle was normal, low idle, no fluctuations. When I increased the throttle and released, the idle returned to the normal low pretty fast.
Also, cranking works every time as long as my finger is over that hole.

The ICS is not doing it's job.
I need to understand if it's a faulty unit or the ECU is not telling it what to do.

The wires to the ICS are good, no shorts, no opens.
Anyone know what voltage I should see at the plug for the ICS?

It sure felt good to hear the engine operate and idle as it's supposed to.

 

I'm a bit hazy on Suzuki EFI as there are so many different systems, all the various KQ engine sizes had a slightly different EFI and face lift (2018 on) models are different again. Firstly has fitting the new ICS sensor removed the fault code?

Check fuel pressure and blow the injector out with an air line. The problem could be the bike is underfueling at idle so idle speed drops, ICS detects this increases fuel supply or, if as you suspect, the ICS controls an extra air supply, as well as the sensor there will be a valve (ICAV) which could be faulty. This overdoes it, resulting in too high an idle which the ICS detects and drops it back again, but overdoes it, to repeat the "hunting" cycle. If it has an Intake Circuit Air Valve check it. Honda 420s often give this trouble and it is usually the ICAV sticking on them.

Trouble is anything can be telling the system to underfuel or overfuel, a temp sensor saying it is hotter or cooler than it really is, for example. Welcome to the wonderful world of EFI.

 

I really appreciate your advice.

first, the error remains after I changed the ICS unit.
I like what your saying about the engine " hunting" for the correct idle. That seems accurate.
My thoughts are; when I completely block the air path that the ICS controls, the engine really seems to operate correctly. If the engine is hunting, why not apply full close to the ICS valve? When the idle is going up and down ( hunting) it never goes as low as when I block the hole. I can hear the air going in through that ICS path and it does not seem to vary, constant fully open path. I think the ICS is not working. I just don't know how to figure out if I have a ( another) bad ICS or are the signals not getting to the ICS for proper action. I believe the ICS I keep referring to includes that valve. The component has a coil inside that surrounds a plunger. It appears to be a voltage controlled solenoid.

Does the fuel delivery system also work to control the idle? If the ICS is always fully open, what is causing the hunting? Does the fuel system have an active feedback function? Modulate the fuel delivered to control the idle. I am not sure, but I don't think that's how it works. I think that's the job of the ICS.

On the other hand, maybe like you said, other functions are failing, causing the ICS to remain fully open.
I will remove and indirect the injector. Blow air through it ( pressure?).

I checked the radiator fluid, the overflow is full, maybe too full. When the engine is cool, the overflow is just above the max fill line. Any thoughts there???

Again, I seriously appreciate your thoughts here.
Additional

 

If the ICS has a solenoid valve attached, that would indicate it also controls air flow, so if both get changed together, this would eliminate that, unless you have got another faulty ICS. Fairly sure code should have gone though. Certainly the red EFI light should go out once running. If it doesn't, the fault is still on, which would indicate a wiring fault. Had endless problems with 450 temp senders and found it was the wires to it. Had one which really thew me, fixed a broken wire and fault still on, tried all sorts of other possibilities before realising other wire to sensor was also broken, but contacting sometimes, and had been working when tested. Don't think there is anything wrong with the cooling, the overflow is an expansion bottle after all. You can't blow right through the injector, but an air line will shift the dirt in the tiny filter which is built into the inlet.

 

I broke down and paid the $15 for the repair manual.
The process to check that idle speed control valve is to carefully measure the wires from the sensor plug back to the ecm.
I did that, the wires are all good.
Next the manual had me asure the pins at the sensor. About 30 ohms across the coils.
I made those measurements and I think the sensor is good. That makes sense, since I just installed it.
With the wires being good and the sensor testing good, the repair manual says the fault is the ecm. Gracious, that's not going to be cheap.

I can't think of much of a worse issue than the one that you described. Finding a broken wire, fixing it and then the second wire was intermittent.

I'm still going to blow out the injector. I'm on my second tank with seafoam.

Have you had any experience with the electronic control module? I'll do the research, but I was wondering if there is a reset or a factory default setting.

On a different note, unrelated here. My four-wheel drive wasn't working and the actuator is a $500 component. I did some research and it ends up there is a small motor inside of the actuator module that burns out. I ordered a replacement on Amazon for $8 and fixed the four-wheel drive actuator last night.
Pretty happy with myself about that.$8 repair versus a $500 replace.

 

I am ashamed to say I got a new ECU for that 450, as we got the dealer to check it on his computer and he got the same code 15 temp sender fault, which I thought was cured. Anyway never had any real ECU problems with Suzukis. Had one early Honda 420 that blew 2 of them due to regulators failing and overcharging. We stopped buying non genuine regs for 420s after that.

 

have you found the issue to this problem? I’m having the same issues and it’s not the things you checked either. Did it end up being the ECU?

 

Worst problem ever!!
I was chasing the actual signal that goes to the ISC.
I removed the ECU and thought I would do a careful inspection.
2 pins on the ECU are broken of right at the point where they come out of the ECU.
it's 2 of the pins that send the signal to the ISC.( Of course )
Shoot me, in the face.

Another pin is looking suspect
I ordered a new ECU from the warehouse in Japan, MegaZip. Pretty good actually. I couldn't find a used ECU anywhere.
It has shipped, due at my house on 9/20/21 (5 more days)

 

I'm the meantime, I took off the ISC and throttle body. Cleaned then very well. Q-tip level cleaning. Especially the home that the ISC guess in. Then I put WD-40 in that hole.
reassembled. The idle hunting is nearly gone and the KQ starts on the first try many times.