Vee2 DIY ISC Sync... - Stromtrooper Forum : Suzuki V-Strom Motorcycle Forums
DL1000A - 2014-2016 DL1000A - 2014-2016 (L4-L6)

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post #1 of 6 Old 11-05-2018, 08:08 PM Thread Starter
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Vee2 DIY ISC Sync...

The Vee2 maintenance schedule calls for a periodic throttle body sync (which is actually just an idle air sync). Problem is that the local shops all quoted me about the same price as just buying the required HealTech SDS tool. So I decided to buy the tool and do it myself.

A few pointers and recommendations...(and questions too)

The ISC must be performed at full operating temperature. This requires that you remove the tank and airbox to gain access to the adjustment screws. Then once hooked up, you have to run the engine to full operating temp. So you either have disassemble a hot bike, run the engine for quite a bit with no air filters, or do a dance with the placing and removing the airbox and tank. I would prefer to disassemble a cold bike and get some single stack air filters that can be fitted onto the throttle bodies during warm up, but I forgot to measure the TB / airbox boot diameter when I had it all apart. Does anyone have a pair of exposed Vee2 throttle bodies or an airbox hanging around their shop that they can caliper for the ID/OD of the filter side?

I did the homemade vacuum balancer (long piece of tube zip tied to a stick with some motor oil in it -- just in case of severe imbalance and ingestion of the fluid, I prefer to not use water). Each end of the tube attached to their respective TB vacuum port and the vacuum will pull to one side or the other until balanced. Once the engine reached the operating temp, I activated the ISC adjustment mode on the HealTech software. BTW, it will not activate (and will auto shut off) if the engine temp exits the prescribed range... so be sure that the engine is well within the range and/or you can see the computer screen while adjusting or you may not realize that the ISC mode has turned itself off.

Prior to the adjustment, my hot engine idle had dropped below the designated target of 1229 rpm, which I can only surmise meant that the ISC had reached its limit and could no longer open up more to restore the higher idle. My idle was down around 850rpm. A small adjustment to one TB screw easily balanced them out, but the RPM was still too low. After that I was increasing both of them to achieve the target idle and balance.

After getting the 1229rpm (which such precision is kind of ridiculous since the reported idle speed bounces around (+/- 50rpm or more) faster than you can read it and can only average it out to about 1220.

After completing the adjustment and balance, I turned off the ISC lockout mode and executed the "reset learned position" test with the HealTech tool as directed in the service manual.

I then checked the Throttle Position Sensor position. Mine was off (too low), so I corrected it. In the future, I'll probably do that TPS adjustment before the ISC adjustment.

Here's where the questions come in...

The bike's idle speed was back to normal, and all was well for the test run around the block a few times. In fact, after a few hot / cold cycles and commutes, it seems that the engine runs smoother and has more grunt. Most likely due to increasing the TPS position back to center where it belongs. However, twice since all of these shenanigans my engine has done the infamous Vee2 idle backfire, both times when the engine was cold and part throttle for just starting to take off from a stop. Did not stall. I have had the ECU recall completed and never really had any notable problems with the backfire before or after the ECU replacement. Perhaps those backfires were just a part of the ECU relearning the "reset learned position" and it won't continue. But it got me thinking about how the ISC was tapped out before my adjustment. As I understand it, the ECU has no feedback from the ISC's actual position (maybe I'm wrong on that...?). So if mine were tapped out, then locked into position during the ISC adjustment, wouldn't that mean that they are still near the end of their throw? I thought about setting the ISC adjustment idle speed a bit higher than 1229 rpm so that they can move back toward middle when the ISC lockout is released by the HealTech SDS; however, I do not know how much throw they have and could easily overshoot and end up tapping them out near the bottom of their throw.

Does anyone know how much throw the ISC circuit has to adjust the idle speed?

Is there any way to determine where they are currently at within their range of operation?

Or perhaps a procedure to center them up again?

If the backfire doesn't recur, then it is all just academic... But I would like to maximize the range of correction available to the ISC circuit so that it can deal with the widest range of environmental changes.

Last edited by Grimmer; 11-05-2018 at 08:09 PM. Reason: typing and proofreading skills could use some remediation...
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post #2 of 6 Old 11-09-2018, 01:22 PM
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Thanks for the post, very informative. I also have the HealTech hardware, and I found it to be easy to use. I have the MotionPro carb synch tool, and it was pretty much a waste of money. I bought an electronic synch tool for next time, which will be within a couple of weeks. I will let everyone know how it goes.
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post #3 of 6 Old 11-09-2018, 03:29 PM
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Grimmer, I have some info for you concerning idle speed which may be helpful.

There is no ISC valve as such. There is no such valve shown in the wiring schematics, nor is there one shown in the Engine Electrical Devices section of my factory Suzuki DL1000A Service Manual.
The ISC is actually a drilled passage in the secondary throttle shaft of the rear cylinder's throttle body. The shaft is controlled by the Secondary Throttle Valve Actuator which, while it is a separate piece, is not available separately from the throttle body assembly. It can be removed for cleaning passages in the throttle body as mentioned for addressing DTC C65 codes for "Idle speed higher than desired" or Idle speed lower than desired".
The secondary throttle valve actuator, by controlling the shaft position through linkage, sets the idle speed based on signals from the ECM.
I posted this a few weeks ago when talking about setting the TPS to the middle position as per the service manual: There is a voltage adjustment to be made for the secondary TPS of .6VDC key on while holding the secondary throttle valve closed.
When I adjusted my TPS I could have...but didnt check/adjust that voltage. If the TPS was off I have no reason to believe the secondary throttle valve position sensor is correct either. I'll adjust it when I have the tank off.
For the C65 codes the 1st 2 trouble area mentioned are 1) air passage and 2) STVA.

As per Page 1C-1 of the Engine Electrical Devices section in the manual:
ISC Valve System Description:
The ISC valve is interlinked with the secondary throttle valve. In the throttle body is provided a bypass through which air volume is varied when the cutaway on the secondary throttle shaft is moved, causing the engine idle speed to be adjusted.
Below this description are 5 cutaway line drawings showing the shaft and throttle body passages related to ISC operation at various angle.

STVA voltage adjustment would, and will be the next thing I'd check when dealing with an ISC situation.
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post #4 of 6 Old 11-09-2018, 04:01 PM Thread Starter
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That would make sense then... The "reset learned position" test in the SDS tool does pertain to the secondary throttle plate system. And the backfire / cough only happened twice and they were both within a half dozen hot/cold cycles of the procedure. It has been about 2 dozen hot/cold cycles since then and the backfire / cough has not recurred.

My ECU recall replacement was done when my junk was all out of whack and I never noticed the bike ever try to bump up the idle speed as the clutch switch closed (?) when the lever was released just a bit. I should mention that I was not aware that this behavior was part of the new ECU programming, or that it is also part of my car's ECU program. I did notice the rpm change in my car, but not for the motorcycle. Either it was too subtle, or my bike wasn't able to make it happen. Before the adjustments and balance, the natural idle of my bike was well below the target as well (almost low enough to trip my "it's gonna die" spidey sense). After the adjustments and balance, the idle has returned to normal AND it started bumping the rpm a bit when starting to let out the clutch lever.

The engine is decidedly running smoother and stronger, and the idle is working normally. Previously, I would always subconsciously short shift before 5K~6K rpm. Since the adjustments, I don't even notice that 5K+ rpm band and have caught myself several times rolling in 3rd or 4th at freeway speeds. I still get a bit of blurr in the mirrors and can occasionally feel a little buzz in the soles of my boots on the pegs, but all in all it seems much happier to run at any rpm. Not bad for a rig with crash bars and a heavy duty (EnduroGuardian) skid plate with highway pegs. However, this doesn't help my fuel economy one bit ...

I'll look into the service manual for that secondary TPS voltage adjustment. It didn't come up while looking over the other instructions, but that manual is pretty well compartmentalized and I didn't go looking for it. I vaguely remember seeing something about it before though. However, the bike is running great as is so I most likely won't need to adjust it.
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post #5 of 6 Old 11-09-2018, 05:38 PM
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Grimmer, look at Page 1C18 and 1C-19
STP Sensor Adjustment
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post #6 of 6 Old 12-16-2018, 03:50 PM Thread Starter
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Originally Posted by MAZ4ME View Post
Grimmer, look at Page 1C18 and 1C-19
STP Sensor Adjustment
I had to lift the tank yesterday to route the wires for my Innovv K2 dash cam install, so I used the opportunity to take off the airbox to check the STP sensor as well as tighten the radiator hose clamps between the cylinders and thermostat.

The STP read 0.591V, so I'll consider that to pass the spec of approximately 0.6V.

Those radiator hoses aren't leaking enough to drip, but weeping just enough to build up crap at the interface and offer a faint whiff of coolant smell when conditions are just right. I suppose replacement is coming soon, although I would hope that they will last until the next coolant change. If the smell backs off it'll probably be OK. Hoses haven't bulged at all, but the clamps were a bit loose.
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