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Discussion Starter · #1 ·
This has me and my friends at a loss. I have a 2003 999 with 40,680 miles on it and up until about 30 miles ago it ran reliably and strong. Out of the blue the idle dropped from 1,200 rpm to 1,000 and would skip a beat or, sometimes, quit running altogether. Thinking that the injectors might be getting gummed up I put some cleaner in with the gas but over the course of about 15 miles or so it got worse. I hooked up the ELM / M5X app and checked to see if I had any fault codes. Yes, yes I did. Some were listed just once while others more than once. Everything from Crank Angle Senor to MAP Sensor to Wheel Speed Sensor to Air Intake Circuit Malfunction to Ignition Coil Malfunction to Cooling Fan Loss of Signal to Immobilizer Invalid Signal and one that is ever-so-helpful, "U165B: Unknown". SMH. I cleared those codes then disconnected the battery, joined the two battery cables together for while to reset the electronics then reconnected the battery. I started the bike up and no codes appeared. No, I did not get my hopes up.

As the engine ran okay once running above idle I opened the airbox and adjusted the idle speed screw back to 1,200 rpm which initially helped a little though the engine did skip a beat every now and then. Hoping to aid the injector cleaner in doing its job I took it out for what we called in my long-past youth an "Italian Tune-up". That is, running the engine at high rpms for sustained periods of time and it ran reasonably well until I did my first WOT blast and got up to around 8,000 rpm and POW! The backfire was LOUD and the engine noticeably skipped a beat. This was going from not good to not good at all!

I read a forum comment that a faulty Crank Angle Sensor can lead to other codes so I changed it with no improvement. In fact, I took it for a short, very short as it turned out, test ride and when I pulled out into traffic it died leaving me at the mercy of on-coming traffic. Fortunately, I got it re-started and out of harm's way quickly then headed back home counting my blessings the entire way.

Since then, I have changed the Speed Sensor, installed a replacement Ignition Coil first on the horizontal cylinder then onto the vertical cylinder and soldered a new Absolute Pressure Sensor onto the instrument panel circuit board. None of these changes showed even a trace of improvement.

In a nutshell, this is what the engine is doing now: When it is started up cold, which it does just fine, it will idle nice and smooth. (I would like to rev it at this time to see if it would backfire at higher rpms but we all know to NEVER rev a cold Ducati, right?) I keep an eye on the engine temperature as it warms up and shortly after the temp gauge stops flashing and steadies around 140 - 145 degrees F the idles becomes unsteady and, more often than not, the engine just shut itself off. It will restart just fine and continue to run rough. If I raise the rpms up somewhere between 3,000 and, say, 5,000, and try to hold it there, it's a lost cause.....the engine will either increase or decrease in speed and refuse to hold a steady setting. If I rev the engine hard from idle it will rapidly gain rpms without a stumble but it will backfire most often around 8,500, sometimes before that speed and sometimes after and always loudly with a huge stumble in the engine.

The plugs, timing belts and fuel filter were changed within the past 100 miles and the plugs have excellent color, light brown with zero signs of oil or excess gasoline, they are dry and the gaps are correct at .030" / .76mm. The voltage display on the dash shows 14.1 at idle and 14.3 when cruising. The battery is a Shorai Lithium and it will reach a full charge in less than a couple of minutes according to its charger even after a long ride.

I am out of ideas and would appreciate any and all opinions from the Forum members. Thank you all in advance.

Rrudytoo
Simpsonville, SC

Tire Wheel Fuel tank Plant Automotive lighting
 

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The beauty of FI is its ability to diagnose itself. There are 6 ways to find out:
1. Wire out of connector.
2. Connector not connected.
3. Sensor short.
4. Sensor out of spec.
5. Wire open in harness.
6. Wire open in sensor.

None met those variables when the phantom codes were cleared. Some causes could be:
Loose battery cables.
Air leak past the sensors, or the spigot holding the throttle body on the engine.
Air assist [leaks] for idle, meaning, no longer an idle cable used to set the idle.
Tight valve.
Compression is?

First code set is?
 

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Discussion Starter · #3 ·
Thank you for your thoughts, Bott. Right now, replacing the ECU is being considered due to the rash of various and sometimes unrelated fault codes. I will keep updating as troubleshooting continues.

Rrudytoo Tire Wheel Fuel tank Plant Vehicle
 

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Glad to help. Let's look at the ECU:
It self codes if it turns into a brick.
It can compute and can light a code up.
It fires and continues to fire up the bike.
It can clear phantom codes.
It is going to be an expensive crapshoot.
 

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If... I'm saying if it has a cam sensor, it could call out a tooth, but it would spit a code I'm assuming. But no cam sensor, I would think it would bend a valve? That would say a single belt would tag the one cylinder, but the other would chug it along if you will. Being a bent valve reads 0 compression, so it would be like starting the bike without the one plug in it.

As the engine ran okay once running above idle I opened the airbox and adjusted the idle speed screw
Let me get this straight. The new belt change, was this running with zero problems?
Let me get this extra straight. Are you telling me that to get to the idle screw(?), you have to remove the airbox cover to get to it? The bean counters said to tell the engineers to find a way to eliminate a simple cable this way?

Or are we moving a screw that is preset for idle and there is no access for an idle screw being it's idle is not vacuum and electronically fixed? Were you sort of messing with those screws? Am not familiar with the generation changes.
 

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I’m not certain that a single tooth off would bend a valve.
Also, if you know where to drill, there is a short cut to removing the air box cover by drilling a small hole to make your adjustments.
Also no cam position sensors.
 

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In my mind it sounds like a temperature related issue affecting electrics - bike gets up to temp then behaves erratically. The ECU is a good call, as I've heard they get fried low down by the header. I'd pull out and unwrap the loom and inspect every single wire/connection. Valves out of spec may not be the main cause but may exacerbate the issue.

Let us know what happens.
 
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