Ducati.ms - The Ultimate Ducati Forum banner

1 - 14 of 14 Posts

·
Registered
Joined
·
629 Posts
Discussion Starter #1
I did a search and found several semi-related threads, but none with quite the same problem that I'm experiencing, and not a solution that I haven't already tried. A little background first.

I bought my bike a little over three years ago, and from the time I got it, it would sometimes cough through the throttle body(s) when taking off from a stop. Not every time, not even half the time, but often enough to be annoying. Sometimes, it would cough severely enough to stall the engine. That was more than annoying. It was embarassing and dangerous in traffic.

I got the bike with fairly complete service records, and it had always been maintained at the local dealer who had a stellar reputation. I prefer to do my own maintenance, so when the time rolled around I did the valve adjust, belts, TPS adjust, and TB sync myself. Miraculously, the cough dissapeared after that service. I was fat, happy and pretty proud of myself for the next 6,000 miles.

So, I just finished another 6k maintenance and the cough is back. It's not as bad as it was when I first bought the bike. You can't feel the bike jerk and it doesn't stall the engine, but once again it bugs the heck out of me. It seems to happen at about 1800 rpm when taking off from a stop, and doesn't affect operation at any other speed. It runs great otherwise.

I've gone back and double checked my work and can't find the culprit. Any ideas or things to check? Thanks in advance.
 

·
Premium Member
Joined
·
5,647 Posts
Too lean idle mix / CO.

Unless you're using a gas tester to measure CO, you're guessing. Last time, you guessed right, this time not as lucky.

Did you mess with the TPS again? Did you adjust the air bleeds again? Do you have a means to adjust fuel trim?

Getting CO at idle correct is a balancing act between proper idle speed, and air bleed / fuel trim settings. You could try fattening it up some by closing the air bleeds a touch, and it’s a good idea to find out which cylinder is spitting at you so you can try to fatten that one up a 1/4 turn or so.

For years, on the ST and my old SS, I did it "by ear". Sometimes it would come out good, sometimes not. What I am telling you here about needing a gas tester and a way to access the fuel trim is from much personal experience. You need these tools to do it right and make it repeatable.
 

·
Registered
Joined
·
629 Posts
Discussion Starter #3
Did you mess with the TPS again? Did you adjust the air bleeds again? Do you have a means to adjust fuel trim?

Getting CO at idle correct is a balancing act between proper idle speed, and air bleed / fuel trim settings. You could try fattening it up some by closing the air bleeds a touch, and it’s a good idea to find out which cylinder is spitting at you so you can try to fatten that one up a 1/4 turn or so.
I adjusted the TPS again because it was off by a few mV, but I didn't change it much. I synced the TBs, adjusted the idle screw and the air bleeds using BikeBoy's procedure. It worked last time but not this time.

I also suspect the air bleeds and have spent over an hour riding around the neighborhood making 1/4 turn adjustments trying to work it out. I can change the problem a little with the air bleeds, but can't make it go away completely. This time it seems to run best with both air bleeds set at 1/2 turn out, but last time they were set at 1-1/2 turn out H and 1 turn out V.

Thanks again for your input.
 

·
Premium Member
Joined
·
5,647 Posts
All add that if you followed the moto one page, you know the settings he specs of 423mv or 2.6 degrees of throttle angle as a place to set the idle stop screw to after base lining the TPS @ 350mv fully closed. Well, I had a problem with that set up at my 24K service. When I set up to those specs, I was unable to get a good balance and had a high idle with lean cough on one cylinder. I found I had a sloppy butterfly pivot at the front TB (the one with the TPS). I could not get a consistent / proper setting.

I ended up buying a set of TBs on eBay off a bike that had 12K on it. Problem solved. Might want to have a look at the condition of your TBs. I now put a drop of lube on the pivots when I am in there.
 

·
Registered
Joined
·
629 Posts
Discussion Starter #5
All add that if you followed the moto one page, you know the settings he specs of 423mv or 2.6 degrees of throttle angle as a place to set the idle stop screw to after base lining the TPS @ 350mv fully closed. Well, I had a problem with that set up at my 24K service. When I set up to those specs, I was unable to get a good balance and had a high idle with lean cough on one cylinder. I found I had a sloppy butterfly pivot at the front TB (the one with the TPS). I could not get a consistent / proper setting.

I ended up buying a set of TBs on eBay off a bike that had 12K on it. Problem solved. Might want to have a look at the condition of your TBs. I now put a drop of lube on the pivots when I am in there.
BikeBoy TPS specs are 150mV inital and 423mV for idle stop. Am I using the wrong setting? It worked fine before :think:

An intake leak is also on my list of suspects. My bike has almost 28k miles on it and things might be loosening up. But, it ran near perfectly before the service, so it's more likely something that didn't get sealed up during reassembly. Maybe I need to hit it with a can of WD-40 and see if I can find a leak.
 

·
Premium Member
Joined
·
5,647 Posts
BikeBoy TPS specs are 150mV inital and 423mV for idle stop. Am I using the wrong setting? It worked fine before :think:

You're correct! Don't know where I came up with 350mv! Just going from my fading memory. Good thing I review procedures before actually doing them!
 

·
Registered
Joined
·
1,470 Posts
TB Or Not TB;

That is The Congestion ...

Consumption be done about It?

Of Cough, Of Cough ...

Not Helpful, but I couldn't resist. :)

(Woody Allen; Everything you wanted to know ...; Jester skit)
 

·
Mr Leakered
Joined
·
8,831 Posts
I think you should go back through the EFI setup and sync again, just to be sure. It is more difficult with the 4s as you guys don't have the trim pot. But, ducatidiag can help you with that. Just dial in a touch more mixture until the cough goes away. I had the same issue on my second attempt. A turn of the trim pot fixed it. The fuel mileage has never really changed.

Have a good one.
 

·
Registered
Joined
·
629 Posts
Discussion Starter #9
I've gone through the setup process twice with no real change. Maybe it's time to get a little more creative. I hadn't thought about trying ducatidiag. I might give that a whirl as well.

I probably won't have much time to work on it this week, so it might be the weekend before I have another update. Thanks again for the help!
 

·
Premium Member
Joined
·
5,647 Posts
Since picking up the VDST software, I no longer use the DVM method. I use the throttle angle method as read by the ECU. When first doing it that way, I did verify my numbers with a DVM, and they do match, at least for zero (I have a Fluke 87 that is calibrated yearly). I forget if the “post set screw position” matched EXACTLY or not, but I'm sure it was close. Now when I do the work, I just pull the linkage and cable give it a gentle tap or two and read zero. Also of note, since changing to the new set of throttle bodies, I have NOT had to make any adjustment to the TPS at all. It's been dead nuts on (for zero) each time I've checked. My thought here is if you had to make an adjustment from the last time, then why? What could have changed? My particular problem was the sloppy pivot at the TPS, yours could be different. It could also be calibration of the DVM you're using. Are you using the same meter? You mentioned it was fine before, and you found you were a few mV off from last time. A few mV is likely within the allowable error for some inexpensive meters (Radio Shack, Home Depot etc.), if that's what you're using, and enough to screw with your set up. The diagnostic tool folks are talking about here sounds real freaking nice. I'd be all over it if I didn't already have the VDST. The real value is the ability to adjust that trim setting. My VDST is used for two primary purposes. Reading TPS angle and fuel trim adjustments. Haven’t really needed the other stuff it does yet as far as trouble isolation. I am starting to wonder if the VDST cable will work with the new software... It does sound pretty neat.
 

·
Mr Leakered
Joined
·
8,831 Posts
When I set up the EFI, I find that the throttle closed reading varies outside of the 150mV +/-5mV. Sometimes it is 140, sometimes 160. The swing across the sensor range on the DMV or now on ducatidiag is very smooth.

My problem, with the link rod and cables disconnected, is getting a repeatable zero number. I try to get a consistent release of the throttle and let it spring closed. Tapping it closed, I'm all over the place (anywhere from 140 to 170mV). I wish there was an index mark or similar. 140 feels jammed shut.

This last time, coming up to the service, the sync was going away and the trim felt a bit lean. On the valve side, I had to mess around with the always finicky (for me) horizontal exhaust shims. I swapped one opener and one closer on the horizontal intake, and one closer on the vertical cylinder. So, the breathing changed slightly.

Setting it up, I came away with a very similar throttle angle to going in, I had to play with the high RPM balance, and only the vert bleed screw was turned out, as usual. I don't know how far. In the end, the trimmer hasn't been touched in the past two services and feels maybe just a tad lean down low. We'll see how it progresses over the next week and the next tank of fuel.

Someday, I want to see what is coming out the exhaust. ;)


Dan,

Ducatidiag uses the same connection as VDST. It is an RS232 connection or an RS232 replicator over USB. Just load up the program and enter your COMM port. It should be good to go.

Have a good one.
 

·
Premium Member
Joined
·
5,647 Posts
Dan,

Ducatidiag uses the same connection as VDST. It is an RS232 connection or an RS232 replicator over USB. Just load up the program and enter your COMM port. It should be good to go.

Have a good one.
That's what I was wondering. A standard serial connection should provide a means to connect the ducatidiag software using the VDST supplied cable. My "garage computer” is an inexpensive eBay find. It's an old Dell running XP with an actual serial connection! Didn’t need the USB adapter.

The flip side of this is VDST "should" work with the inexpensive cables you guys are getting to use with Ducatidiag. Before I ordered the VDST, I was able to download the software from the Technoresearch site. I was able to play around with it, but of course not connect to the bike. When my kit came, with the cable and disk, I didn't load it from the disk, I just used the software I downloaded and everything worked. No license number was give to unlock anything. It seems the money spent was for the cable... Kind of a pisser now that this is available, especially if those cable s work with the VDST software. Oh well, like all those who spent the big money on actual DP ECUs before the availability of these re flashed units, that’s just how it is…
 

·
Mr Leakered
Joined
·
8,831 Posts
When I was flip-flopping about buying the VDST software, I was happy that I wouldn't have to mess with the RS to USB issues since I had a classic COM port also. Needless to say that I am happy that I never pulled the trigger.

Even the simplest OBD gadgets were crazy expensive until recently. The big deal is that you have had a lot of utility out of it.

Of course, the same complexity and hurdles will need to be overcome with whatever is next.

Have a good one.
 
1 - 14 of 14 Posts
Top