Non-linear TPS reset - Stumble at idle

[rule62]

My 04 620 just started a new behavior.  At idle, it stumbles.  It almost seems like at times, it isn't firing.  Recently, I replaced the timing belts, adjusted the valves, replaced the fuel filter, replaced the spark plugs and changed the oil.  When the problem began, a buddy of mine asked when was the last time I changed the battery.  I told him that I was still running the stocker, and that I had never put a tender on it.  The bike has about 16,000 miles on it.  We agreed that I had gotten my money's worth out of the YUASA and that perhaps a new battery would solve the issue.  I installed the new battery, but the problem persists.

Volts off = 12.85
Volts at idle when first turned on = 13.05
Volts at 4000-4500 rpm = 14.5

Here's the fun part:
As the bike warms up, the voltage at idle begins to drop.  The hotter it gets, the more variation.  The volts begin to drop below the 12.85 reading and eventually, the stumble behavior begins.  The bike runs like butter when it's moving along, but at idle it stumbles and wants to die.  The regulator/rectifier is getting pretty hot, but I thought that was normal.  

I'm going to clean all of the electrical connections and protect them all with some dielectric grease, as well as inspect and clean the ground.

Anyone had a similar experience?  Thoughts about stator, rectifier/regulator, anything?  Would a poorly set TPS or throttle sync cause a stumble at idle.  How about the thick 20w50 oil I'm running?

Thanks,
Ryan

[rule62]

So... I disconnected the VR and relocated (flipped) it so that it's more out in the open and it can get a better flow of air over it for cooling.  Cleaned all of the connectors.  The ones to the VR looked like they my have had a little corrosion in there.  Cleaned and reconnected the ground to engine block.  I also took out the block-off bolts I had in my TBs and replaced the little nipple connectors I use to sync.  I just ran a hose from one to the other.  My thoughts are that the connection between the two may smooth any slightly non-sync'ed areas in the rev-range. 

Ready to ride and check it out... and wouldn't ya know it... It's about rain in Phoenix, AZ!

I wonder if some of the slight corrosion I saw in the connectors may have caused the VR to not work properly.  And/or if it caused any irrepairable damage. 

Please post up your experiences with bad regulator/rectifiers so we can compare symptoms and maybe help some poor shlub in the future.

Thanks,

[Speeddog]

The stumble at idle may be a voltage issue, or just may be due to the engine temp and how the ECU adjusts fueling dependent on it.

The ECU itself is voltage sensitive, I've seen a bad ground at the cases keep an S2R1k from starting.

Seeing as you've just adjusted the valves, that muddies the water a bit further.
What clearances did you set the valves to?
Did you sync the TBs?

I haven't seen any late-model regulators fail, but it doesn't get as hot here as in Phoenix.
Doesn't mean yours is good...

The RRs do get hot, hotter than I'd like to see, but they seem to deal with it.
Keeping it cooler definitely won't hurt it.

[rule62]

Valves are all within spec.  Openers at 5, closers at 1.  The stumble began after replacing a valve guide seal, putting some really thick oil in and taking it on a 750 mile ride through the mountains where we saw a bunch of rain and some really cool temps.  While riding, my indicator actually dipped low enough to blink "LO" like it does when first started.  I thought it was just the altitude (8000) that my bike didn't like.  No O2 sensor, so I figured it was just running rich and flooding a little at idle.  Back in the valley (alt 1000) the crumby idle persists.  The regulator is getting burning hot.  Can't keep my hand on it when the problem shows up.  I don't have any electronic diagnostic interface or software.  I'm trying to narrowe out the mechanical issues before I have to take it to the dealer$hip. 

Do the ECU's "learn" like a car's ECU?  I wonder if it tried to compensate for the rain and cold air temps on the trip and now it can't re-adjust.  I have no idea.  Can the ECU be reset without an interface or software?

[yotogi]

Do the ECU's "learn" like a car's ECU?  I wonder if it tried to compensate for the rain and cold air temps on the trip and now it can't re-adjust.  I have no idea.  Can the ECU be reset without an interface or software?

Some do. I know that the one on my 06 S2R1000 does some learning in closed loop mode. I believe that you can "Reset" the ECU by disconnecting the battery overnight. Your shop might be able to clear it also, I can't imagine that they would charge you much if anything if they are worth their salt.

[Speeddog]

Only the bikes with O2 sensors have ECU's that can 'learn'.

[rule62]

I picked up a couple of used RRs.  One from a 695 and another from an S4.  I'll keep ya posted.

[rule62]

Switched out the regulator.  Still stumbles at idle.      Runs smooth everywhere else.  Think it may be the TPS.  I've heard tale of those things drifting out of range over time.  After the 3000 revolution (3 min) warm up time where the ECU runs rich, is when the problem starts.  I think it's a fueling issue.  If the TPS if out of range, the ECU may be sending the wrong signal to the injectors.  Gonna do a complete TPS calibration and TB synch real soon.  I'll post up when complete.

On another note: I just went for a ride with a few 1000 DS's.  Bumped off of the rev limiter pretty hard in 1st gear trying to get the front up in the air like the rest of the gang (not so easy on a 620 with an extra inch of height in the back).  Next few idles at lights, after the rev limiter bump, seemed smoother. 

Still gonna do the TPS and TB's.

[rule62]

Stumble at idle...
Replaced Battery...   
Replaced Voltage Regulator/Rectifier...   
Replaced Horizontal Spark Plug Coil...     
Replaced Spark Plug Wires...     

Finally read enough to feel comfortable with resetting the TPS.  The specified reading at idle should be 434 mV.  Mine was reading 325 mV.   Loosened the set screws, rotated it a little, dialed it in at 434 mV running and warmed up at 200 degrees.  (The entire TPS reset process is a bit more complicated, so I opted for the abridged version.)  I did not close the butterflies entirely and set the base level at at 0 degrees open to 150 mV.  The LH throttle-body stop was too hard to get to and the factory yellow paint was way to thick to get out of the little 2.5 allen hole.  I just took for granted that the butterflies were at the correct degree of opening as it was set, and then adjusted the mV on the TPS to 434 mV. 

Maiden voyage is this evening.  Wish me luck.

Update...

I think we have a winner.  Definitely could use a TB synch, but the bike doesn't seem to want to cut out when I'm waiting at a light.  Idles a bit higher now ~ 1150 rpm or so.  Hopefully that'll be it.  I was so intimidated to mess with the electronics. 

[rule62]

update

http://ducatimonsterforum.org/index.php?topic=31155.msg540495#new

First of all... Thank you Mr. Black

http://www.bikeboy.org/ducati2vthrottleb.html

I went to the Toyota Dealership on Wednesday to have them take a look at a rattle I had in my driver's side door.  Loose window regulator.  They tightened it up and while they were at it, decided to give me a new battery for free.  Power Toyota in Tempe, FTW.  Stopped by the parts counter to sign the warranty paperwork and spotted a multimeter for sale $9.99.

Now with multimeter in hand, I was ready to tackle the TPS reset long version!
(The short version was just setting it to 434 mV at idle without setting the base level or messing with the throttle stops at all.)

This time I did not set the TPS with the bike hot.  All work was done with the bike cold, just flipping the key to on, the bike not started.

Observations:

The short version TPS set I did at idle with the bike on and hot (220 degrees) was set at 434 mV.  The initial TPS reading I took with the bike cold and not started was 448 mV. 

I backed out the RH throttle stop pretty far.  I did not remove it, although it is indicated that you can just get rid of it in Brad's directions.  It is still there but is serving no purpose at this time.  The LH throttle stop is the only one you need.

I loosened the balance adjuster 2 full turns, as indicated, before messing with the LH throttle stop.  I returned the balance adjuster to its original position after setting the TPS.  I will most likely benefit from another TB synch in the near future. (Perhaps when I install the PCIII I just scored for cheap $$$.  Thanks D!)

After backing out the LH throttle stop and closing the butterflies, the base TPS reading I got was 290 mV.  It's supposed to be 150 mV.  I thought that was pretty far off, and when you take the mV relation to the butterfly opening, may be part of the reason that my bike would not idle with the air-bleeds closed the last time we synced the TB's. 

I set the TPS base setting at 150 mV as indicated.  Then I began adjusting the LH throttle stop to get 434 mV exactly as indicated.  After that I returned the balance adjuster to where it was previously by tightening it 2 full turns.  Put the air-box back in and fired her up.

The bike was idling pretty high.  Both of the air-bleeds were backed out pretty far from the last time we messed with them after synching the throttle bodies.  I closed them both and let the bike come up to temperature.  At 200 degrees, I backed each air-bleed out only 1/4 turn to get an idle speed of about 1150.

Oh yeah... I also put my original voltage regulator back on.  Really no reason.  Just to keep the part #s matching as much as possible.

Tomorrow will be the shakedown run.

[DucHead]

How did you hook up a voltmeter to the TPS?  What ECU do you have?

[rule62]

I used a razor blade to expose some of the bare wire from the 2 outside leads running into the TPS.  Then just touched them with the probes from the volt meter. 

5.9 ECU

[DarkMonster620]

I used a razor blade to expose some of the bare wire from the 2 outside leads running into the TPS.  Then just touched them with the probes from the volt meter.  

I had something like that, bought a PowerCard from DesmoTimes and voila, problem gone, $269.00 plus S&H...

5.9 ECU

[DucHead]

I used a razor blade to expose some of the bare wire from the 2 outside leads running into the TPS.  Then just touched them with the probes from the volt meter.  

5.9 ECU

thanks.  I'm often reluctant to do the most obvious thing.  

I was really hoping I could find a set of those amp connectors.

[brad black]

i've never found the small tps connector.  someone told me it was a delco crank angle sensor connector, but then you have to find the female as well.

air bleed setting has a big influence on idle mixture, and that can have a big impact on idle quality.