1998 916 biposto misfire from idle when warm only - Ducati.ms - The Ultimate Ducati Forum
  • 2 Post By davy.j
  • 1 Post By vtwin
  • 1 Post By TomTom
 
LinkBack Thread Tools
Old Jul 7th, 2019, 8:42 am Thread Starter
Junior Member
 
Join Date: Feb 2015
Posts: 19
Question 1998 916 biposto misfire from idle when warm only

Hi All,

I am having a missfire issues when i blip the throttle from idle when the bike is at temperature only.
The bike starts well from cold, throttle response sharp until it warms up.

I think i have this issue since the bike has be fitted back with OEM exhaust and EEPROM.

What i did alredy and didn't help:

- Checked air temp, water temp, pressure sensors resistance when cold and warm -> ok
- Check harness wiring up to ECU -> Ok
- Checked Throttle body resistance -> Ok
- Did the throttle body setup procedure of service manual -> Ok
- Balanced both cylinders as indicated i the service manual -> OK
- Set the idle using the bleeders from fully closed up to correct idle rpm -> ok (1.5 turns from close)
- Set the mixture pot of 1.6 ECU according to the 1/3 turn anticlockwise from lean stumble point (I do not have the CO meter)

I can see that the bleeder setting has somehow a slight inflence of the misfire but cannot find the sweetspot.
Also the mixture pot has little influence of this misfire behaviour. What might give you a clue is that i cannot reach the stumble point with the mixture pot on the rich side..

I don't know what more to do at this point and would like to ask your advice as last chance before i have to walk in a ducati workshop.

Here the video:
The warmer the bike the worse the missfires. If i hold the idle above 2000 rpm the throttle response is good.

Am i missing something in the sync/mixture setup (is it so complicted to setup??) ? Any suggestion on what to check more ?

Cheers

Last edited by tombsix; Jul 7th, 2019 at 8:48 am.
tombsix is offline  
Sponsored Links
Advertisement
 
Old Jul 7th, 2019, 10:17 am
Senior Member
 
Join Date: Apr 2012
Location: Boyertown, PA, USA
Posts: 318
First thing to do is to check the battery and the grounds. My 916 runs like absolute shit if I am not getting 13.5 from the batt.

Re your set up, I believe that the injection system is open ended meaning that it will not automatically adjust to a change in intake or exhaust. There are guys smarter than me on this site who know this particular stuff a lot better than I. @ducvet is one of them. Be patient, the answer is here.

Failure is not an option 1995 Duc 916,1994 Bim DB2,1986 Duc MHR Mille, 1974 Duc 750 Sport, 1965 Duc Monza
casor is offline  
Old Jul 8th, 2019, 3:45 pm Thread Starter
Junior Member
 
Join Date: Feb 2015
Posts: 19
Thanks for the hint. I am indeed using a ligthweight lithium battery and i am reading 13.2 Volts engine turned off, can this be the issue ? How high is the OEM battery voltage ?

Weird stuff is that it only happens when warm !
tombsix is offline  
 
Old Jul 8th, 2019, 4:00 pm
Come in Spinner :)
 
davy.j's Avatar
 
Join Date: Oct 2009
Posts: 7,162
Images: 146
Battery type makes no difference, check the connection on your coolant temperature sensor, (not the fan switch)
Sounds like its staying rich due to lack of signal from the sensor to the ecu.
Check the chip is seated properly with no bent pins seeing as you've swapped the exhaust and chip back to stock.
SS904 and ProphetPVD like this.

2000 853
2007 Cagiva Mito.
1980 and 1978 Ultra lightweight Yamaha SR500 Cafe Racers
1967 500cc Ultra lightweight Triumph Daytona Cafe Racer
davy.j is offline  
Old Jul 9th, 2019, 4:19 pm Thread Starter
Junior Member
 
Join Date: Feb 2015
Posts: 19
Thanks.

No luck that has been already checked..

When the bike is too rich at startup when cold it run smooth.
If it would stay too rich when warm and i would lean it using the mixture pot it should improve. But it doesn't. I tried until it stumbles on the lean side, no luck to make it better.

Really weird issue though..maybe related to ignition after all if the mixture doesn't influence that much..Maybe a bad plug..

Last edited by tombsix; Jul 9th, 2019 at 4:25 pm.
tombsix is offline  
Old Jul 10th, 2019, 5:00 am
Prolific Poster Award
 
SS904's Avatar
 
Join Date: Sep 2004
Location: Coventry, CT, USA
Posts: 5,549
Garage
Trim pot has a negligible effect on anything beyond idle or a cracked throttle, like at cruise speeds. Think of it as a pilot screw / jet (in combination with the bleed screws) from carb days. If it is going really rich when it's warm and you're sure the TPS is set correctly and all the sensors have tested good, try refitting your old EPROM since the problem started after you changed it back. If no change, may be time to get your hands on a second ECU to test.

It seems it's going really rich in the vid, but is that what you think is happening? Plugs show dark, sooty exhaust, eyes watering in the garage??? Doesn't seem like it should be the case since you say it runs OK when cold, but worth checking for blockage in the original exhaust you installed. Intake blockage as well. Maybe a family of mice built a house in there...

Dan. "Painfully mistaking my big talk for the truth" Samantha Fish.
2003 ST4s (The Truck)
1995 916 (Junk Yard Dog)
SS904 is offline  
Old Jul 11th, 2019, 4:41 pm Thread Starter
Junior Member
 
Join Date: Feb 2015
Posts: 19
Quote:
Originally Posted by SS904 View Post
Trim pot has a negligible effect on anything beyond idle or a cracked throttle, like at cruise speeds. Think of it as a pilot screw / jet (in combination with the bleed screws) from carb days. If it is going really rich when it's warm and you're sure the TPS is set correctly and all the sensors have tested good, try refitting your old EPROM since the problem started after you changed it back. If no change, may be time to get your hands on a second ECU to test.

It seems it's going really rich in the vid, but is that what you think is happening? Plugs show dark, sooty exhaust, eyes watering in the garage??? Doesn't seem like it should be the case since you say it runs OK when cold, but worth checking for blockage in the original exhaust you installed. Intake blockage as well. Maybe a family of mice built a house in there...

Thanks for this suggestion. When warm it doesn't smell that much benzin (like when starting cold) so i don't think it runs so rich ! The bike is still very much ridable without backfire whatsover while driving.. I'll try to fit again the ultimap EEPROM as I have the original in right now and check exhaust. I went from a race exhaust to OEM back. No chance for the mice nest neither ;-) I'll spend a bit more time on the bike this weekend..
tombsix is offline  
Old Jul 12th, 2019, 12:31 am
Senior Member
 
vtwin's Avatar
 
Join Date: Nov 2005
Location: _, Finland, FIN, the EU
Posts: 795
Garage
Images: 1
Just a quick idea - what about fuel pressure? is the pressure regulator ok? injectors? I just troubleshooted a friends RC51, the regulator was leaking fuel to the throttle body --> Crazy rich mixture. Are the Marelli regulators prone to fail?

ping @TomTom to the red courtesy phone.
ProphetPVD likes this.

Last edited by vtwin; Jul 12th, 2019 at 12:34 am. Reason: ping
vtwin is offline  
Old Jul 12th, 2019, 10:45 am
Senior Narcissista
 
TomTom's Avatar
 
Join Date: Jan 2005
Location: Newbuying, Flatoutcounty, Sweden
Posts: 5,737
Garage
Sorry, I have no idea :/ Never heard of a p-regulator out of order on a duc.
Has anything been done to the bike lately?
The trimpot mentioned has a huge effect at low revs, if you just breathe on it itll turn one percent in co, could be it if the bike was tuned for the non oem eprom and had the oem installed after.
vtwin likes this.

Last edited by TomTom; Jul 12th, 2019 at 10:51 am.
TomTom is offline  
Old Jul 27th, 2019, 8:22 am Thread Starter
Junior Member
 
Join Date: Feb 2015
Posts: 19
Hi,

I've just done a oil change, filled the tank with new fuel.

Trying to figure out this systematic problem when it warms up I have disconnected the water temp sensor while running. Doing that the engine does even more these misfires.

If i disconnect the temp sensor do you know if the ECU defaults to cold or warm ?

If it defaults cold then i guess i am running much too rich I guess.
Runs well when cold, probably already on the rich side then goes much too rich while it warms up, right ?

Funny thing is that if i would be already very rich then I would manage to reach the rich stumble point with the mixture pot easily but I cannot reach it ! It is somehow contradictory to me.

Next i was thinking to check:

1st Borrow a CO meter to set this mix pot properly. May be sensitive but i don't belive the issue is there as i would have found the sweet spot already.

Then

- Fuel pressure
- Try without air filters (was cleaning them and spray with air filter oil, maybe i clogged them..)
- Check OEM exhaust if somehow restricted..
- Swap the eprom

makes sense ?
tombsix is offline  
Sponsored Links
Advertisement
 
 

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Ducati.ms - The Ultimate Ducati Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in









Thread Tools



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome