Ducati.ms - The Ultimate Ducati Forum banner

1 - 11 of 11 Posts

·
Registered
Joined
·
233 Posts
Discussion Starter #1
The bike gets up and goes but at partial throttle will develop a miss and stumble. The front plug was quite dark and a replacement made it better but still noticeable. I'm only getting 70miles to a tank now. It's running rich on the gas analyzer.
Any ideas what might cause this?

Thanks
 

·
Registered
Joined
·
233 Posts
Discussion Starter #2
So apparently the TPS adjusted its self to well out of range. Anyone ever hear of a TPS moving on it's own?
 

·
Registered
Joined
·
1,443 Posts
It happens, that's why it's spec'd to check and adjust it's setting during full services. I have a similar issue right now on my '03, not sure it's the TPS but I'm going to check it.
 

·
Registered
Joined
·
724 Posts
So apparently the TPS adjusted its self to well out of range. Anyone ever hear of a TPS moving on it's own?
The TPS shouldn’t “Move” on it’s own unless it was never tightened completely. After use, engine wear, component wear, etc, does require periodic adjustment/checks. To just go rich (assuming the the TPS was tight) from running normal, it is possible one (usually not both -- but not saying it can‘t happen) injector is not atomizing the fuel correctly, partially plugged -- dripping or more of a solid stream instead of an atomizing mist, and possibly not seating completely (shutting the fuel off completely between firings).

Maybe run some injector cleaner through it a couple of tanks worth. Did this happen after a recent fill-up? Air filters clean/dry? Did the bike get wet?
 

·
Registered
Joined
·
233 Posts
Discussion Starter #6
Thanks YB. There was no specific event that caused this to happen. It did sprinkle the day i noticed this issue but just a few drops. The TPS definitely moved. It was put on the computer and it was at 2.3 instead of 1.something. It ran fine for 2 miles after put back to 1.something but the missing and stumble has reared it's ugly head again. There is definitely something to the injectors maybe being stuck open because my fuel economy is horrible now and on the sniffer it's running rich. I'll try some injector cleaner for sure and report back. Thanks a bunch.

Kevin
 

·
Registered
Joined
·
724 Posts
I’m assuming when the TPS was checked the butterflies were “Completely” closed? Was the TPS actually found to be loose? After Initially setting the TPS to the correctly voltage (and it is worth the time it takes to get it exact - not the plus/minus setting) it is increased to an Initial idle voltage, but that voltage is only a setting to get it to idle, after that it will end up somewhere close but it’s not really important were it ends up as long as the correct setting was accomplished with the butterflies closed.

Is the miss you are feeling a sharp drop as in ignition? Or is it more of a starvation type miss, which seems unlikely if it is running as rich as you say. Could be something like a Coolant Temp sensor, Air Temp sensor, or possibly the Absolute Pressure sensor sending incorrect info to the computer. Measure the readings on these to verify.
 

·
Registered
Joined
·
233 Posts
Discussion Starter #8
The TPS is set correctly and is holding its position yet it's still runnng super rich. I'm getting 70 miles per tank ad you can see the richness out of the exhaust when you brap the throttle.
 

·
Registered
Joined
·
724 Posts
I guess the question is did this just happen? Has it been a gradual richness or over night? My first thought is air cleaners (other then the previous posts)..

You say you’ll see rich condition smoke when the throttle is blipped -- to a certain extent this is normal. - 70 miles per tank isn’t - What is the CO%? -- 3.5%- 4% is about normal, and as much as 6%, but I consider that on the high overly rich side. I get about 115-130 miles before the light comes on - (2000 - 996) - no, that‘s not a limp wrist - ha!. Check the easy things first.

As long as the TPS is set correctly “without question“ since this controls the amount of fuel introduced through the injector (but not the only factor) through throttle position, the TB/cylinder balance adjustments need to be gone through to verify they are correct (a large part of getting it to run correctly and also influences the mixture). As long as tune-up items are no longer questions (including clean air filters, plugs, fresh oil [if let go too long can affect mileage] chain lubed), also consider riding style - valve adj ( how many miles?) -- and none of these are contributing to the lower mileage, I think the sensors would be the next check.

Another thought: Are you filling the tank completely?
 

·
Registered
Joined
·
3,642 Posts
The TPS on the testastrettas is in a fixed position, unlike the desmoquattros which is adjustable. To set the TPS on a 749, you need a mathesis or other diagnostic equipment to set the TPS reference signal to the ECU.

The OP stated the the symptom occured with the front cylinder after a sprinkle, so a likely cause is the front coil shorting; which has been an issue with these bikes. Try packing the coil lead with some silicone grease, or possibly replace the coil if it continues
 
1 - 11 of 11 Posts
Top