06' ST3s surging issue - Possible culprits - Ducati.ms - The Ultimate Ducati Forum
 
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post #1 of 4 (permalink) Old Aug 15th, 2019, 4:05 pm Thread Starter
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Question 06' ST3s surging issue - Possible culprits

My ST3 has been lonely for far too long because I've been working (slowly) to narrow down a diagnosis before bringing her to a shop.

Starts easily, plenty of power, idles pretty good, if hunting around a bit. Under light throttle (cruising or through a turn for example), I can feel the power surging a little, as if I'm making rapid small adjustments.

Even though I drained the tank before winter storage, I neglected to drain the fuel lines. Changed the spark plugs, threw in some techron, and tried a good high speed run int the mountains. After getting back into town, my butt dyno is telling me the problem got worse

So, I sent the injectors out to be professionally tested and cleaned, but at 24kmi, one was only slightly out of spec (3% or so). I also replaced the fuel pump and filter, and found the filter screen on the pump had what looked like a pea-sized hairball right under the pickup. Of course I cleaned the screen before fitting the new pump.

After these changes, it seems the issue is less acute, but its frequency has not changed. A little annoying on the highway, but unnerving when the balance changes in the middle of a corner

I tested the fuel level sender while the pump assembly was out, and noticed the Ohm reading moved around a bit if I wiggled the harness wires near the flange fitting/sleeve. Testing the connector on the sender itself, readings are pretty consistent. Is this harness failing slowly (ethanol breaking down the epoxy)?

What's the next most likely culprit given the bike's age? Vacuum leak somewhere? Other electrical faults ?

Thanks!

2013 Hyperstrada 821 | 2006 Multistrada 620 | 2006 ST3s
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post #2 of 4 (permalink) Old Aug 15th, 2019, 9:57 pm
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original ecu or dp?

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post #3 of 4 (permalink) Old Aug 16th, 2019, 4:30 am
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The ‘06 ST3 is the first year that Ducati used a lambda sensor on this engine. The fuel system runs lean and surges at lower rpm’s. My ST3 did the same. I put on a G2 throttle tamer that made the throttle response a bit more fine tuned and installed a Fat Duc between the lambda sensor (O2 sensor) and the ECU. The Fat Duc fools the ECU to make the mixture a bit richer when the sensor is active. This resulted in a much better (not perfect) ride.

Ultimately, the solution came with an ECU change and removal of the lambda sensor. You can have the ECU reflashed to achieve this too...my ECU died so it was the opportunity to make the switch!


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Mike
2006 ST3 - 2004 KLR 650 (the Truck)
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post #4 of 4 (permalink) Old Aug 19th, 2019, 12:27 am Thread Starter
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Thanks for the suggestions. How can I find out if it's a DP ECU? I'm the second owner and don't have any documentation the ECU was changed.

2013 Hyperstrada 821 | 2006 Multistrada 620 | 2006 ST3s
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