rpm surge 2003 sportster 4tec
- Thread starter Drdjewel
- Start date
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- Tags
- rough idle rpm surge sportster
- Status
some success
My initial thought is that it could be the TPS - throttle position sensor. And is still may be. But it is an expensive part ($200+) and not easy to get to. You need to take off the throttle assembly. But I just had an experienced mechanic do some routine maintenance and he noticed that something was missing. Part of routine maintenance is lubricating the throttle assembly. There is a fitting on the throttle body into which you spray lubricant peroidically. This assembly is usually capped. Mine was missing. So we attached a 2 ft piece of silicone tubing onto that assembly to facilitate spraying lube in there. I then clamped that. It seems to have helped. I would not say it eliminated the problem, but it seems better. It is possible that having that assembly "open" allows air to get sucked in, sort of like a manifold leak. So, check if you have that fitting. Also, I notice this problem is worse when the engine is cold. Improves a bit after running. Lastly, I find the engine settles in better when you overshoot your intended rpm on the throttle then back down to where you want it, as opposed to inching up. These fuel injected engines are finicky - you are relying on a sensor to formulate the mix rather than a simple carb. Let me know if any of this helps. Good luck.
My initial thought is that it could be the TPS - throttle position sensor. And is still may be. But it is an expensive part ($200+) and not easy to get to. You need to take off the throttle assembly. But I just had an experienced mechanic do some routine maintenance and he noticed that something was missing. Part of routine maintenance is lubricating the throttle assembly. There is a fitting on the throttle body into which you spray lubricant peroidically. This assembly is usually capped. Mine was missing. So we attached a 2 ft piece of silicone tubing onto that assembly to facilitate spraying lube in there. I then clamped that. It seems to have helped. I would not say it eliminated the problem, but it seems better. It is possible that having that assembly "open" allows air to get sucked in, sort of like a manifold leak. So, check if you have that fitting. Also, I notice this problem is worse when the engine is cold. Improves a bit after running. Lastly, I find the engine settles in better when you overshoot your intended rpm on the throttle then back down to where you want it, as opposed to inching up. These fuel injected engines are finicky - you are relying on a sensor to formulate the mix rather than a simple carb. Let me know if any of this helps. Good luck.
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