This thread looks empty. Did you resolve the issue? My first thought would be overall service and maintenance. e.g. have you had the valves inspected/adjusted if you have substantial mileage? My next guess if the bike is in decent mechanical condition and the service is up to date, would be to do a fuel pressure check. The fuel pumps are pretty competent these days but it can be a pretty straight forward test with a trip to harbor freight. The quantum and caltric pumps are cheap but I have personally had some spotty reliability and fitment problems in the past. Interested in what cam of it in the last almost full year.
Intermittent low idle on 2007+ SV650
I have a low idle rpm condition that happens occasionally with a warm engine, when pulling in the clutch when the bike is coming to a stop. The rpm will drop down to 1,000 rpm for a few seconds before going back up to normal 1300 rpm idle speed. Once in a while the engine will stall. This is on a 2008 SV650 with electronic idle speed control. There are no FI codes for the ISC valve or anything else.
Are there any common issues that cause this?
I did have some dust in the airbox from a rodent nest situation a few years back. I ran some Seafoam through the throttle bodies and they still look pretty clean. I'm thinking of spraying some Seafoam or carb cleaner into the ISC valve (idle speed control valve) hose that connects to the airbox. I'm thinking that it will be sucked through the ISC valve and then through the hoses that connect to the throttle bodies. Is there any good reason not to try this?
Are there any common issues that cause this?
I did have some dust in the airbox from a rodent nest situation a few years back. I ran some Seafoam through the throttle bodies and they still look pretty clean. I'm thinking of spraying some Seafoam or carb cleaner into the ISC valve (idle speed control valve) hose that connects to the airbox. I'm thinking that it will be sucked through the ISC valve and then through the hoses that connect to the throttle bodies. Is there any good reason not to try this?
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The valves are in spec. Bike has 37,000 km on it. I would suspect that if the fuel pump were failing, or if the fuel filter were clogged, I would first notice running issues at higher engine load when the pump needs to provide a lot of flow, but maybe this isn't always the case?This thread looks empty. Did you resolve the issue? My first thought would be overall service and maintenance. e.g. have you had the valves inspected/adjusted if you have substantial mileage? My next guess if the bike is in decent mechanical condition and the service is up to date, would be to do a fuel pressure check. The fuel pumps are pretty competent these days but it can be a pretty straight forward test with a trip to harbor freight. The quantum and caltric pumps are cheap but I have personally had some spotty reliability and fitment problems in the past.
I just made the post a couple of days ago. You must have looked at my forum joined date 🙃. Anyway, I do have an update. I put the bike in dealer mode to check the TPS calibration, which was in spec. The 2007 service manual says that entering dealer mode and then cycling the ignition on and off also sets the ISC valve pre-set position. Not sure what that means exactly, but it's apparently required to do this procedure after removing or replacing the ISC valve. After doing this, the warm idle rpm seems to be slightly higher, and I haven't noticed any dips in idle rpm since, but I've only ridden the bike for 20 minutes or so, and maybe didn't get the engine warm enough to replicate the issue. I'll provide an update once I get some more riding in.Interested in what cam of it in the last almost full year.
I could see the Idle Speed Control being an issue. Possibly lowering the idle under low vacuum too much and ultimately shutting the butterfly all the way, especially under decel. The Throttle Position Sensor and the Manifold Absolute Pressure sensor would be an input, telling the throttle bodies how far to open/close the output (ISC). It is just odd that it would be altering itself all willy nilly. Because they are set functions. Resetting the ISC would be reminding the ECU where the ~0-5mv range is at closed throttle. I am not familiar with the Suzuki ECUs but I know that early Mirelli 1.5 ecu would create absolute ridiculous fuel mapping and idle air control conditions if it was not set the correct millivolt readings when closed. But, if you have not altered any of the settings in the throttle bodies and they are clean, there is no reason for those to change. Maybe any small discrepancy is resolved by resetting it in the dealer mode. I have just seen lots of smaller machines, primarily the honda metros and vespa 150/300s have weird idle problems under high vacuum(map)/low rpm(closed throttle/tps) such as coming to a stop or coming down from ISC/auto-choke settings to idle when cold. 20 minutes should be enough time to get the engine warm enough to kick on the fans for a water cooled machine.
That being said, I would like someone with actual mechanical and electrical engineering knowledge to educate me on my primitive concepts. Stoked to hear what resolves it.
That being said, I would like someone with actual mechanical and electrical engineering knowledge to educate me on my primitive concepts. Stoked to hear what resolves it.
My thinking is that the ISC valve monitors idle rpm, and adjusts the ISC valve position to maintain the set idle speed. If the idle speed is low, that suggests that there is not enough airflow through the valve and hoses to the throttle bodies. This could be due to a sticky valve that can't go fully open, or something clogging the valve or hoses, restricting airflow even when the valve is fully open. The other possibility is that the ECU wasn't applying enough voltage to the solenoid to fully open the valve, and maybe the dealer mode reset allowed it to learn to apply more voltage, though I don't understand why it wouldn't just be programmed to max out the solenoid voltage if the engine was struggling to idle.
I need to wait for the weather to warm back up before I call the issue solved, but for now the bike is running fine. The fact that it only happens with a warm engine makes sense, since when the airbox is heat-soaked, the hotter air is less dense and more volume needs to flow through any restriction to achieve the proper mass flowrate. The problem most often occurs after decelerating from highway speeds in warm weather, when the airbox would be heat-soaked.
I need to wait for the weather to warm back up before I call the issue solved, but for now the bike is running fine. The fact that it only happens with a warm engine makes sense, since when the airbox is heat-soaked, the hotter air is less dense and more volume needs to flow through any restriction to achieve the proper mass flowrate. The problem most often occurs after decelerating from highway speeds in warm weather, when the airbox would be heat-soaked.
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