Rough running in very narrow range - SOLVED

[Guest jmnvhc]

Hello all,

 

I recently added Mistral muffs and PCIII to my bike, and loaded it with the appropriate map (Dynotune happened to have one already for Mistral muffs and stock everything else). This is more FYI, because I noticed the following issue before I did anything to the bike.

 

If the bike is running between 2500-3000 RPM, AND the throttle is just baaaarely open (for example, running on perfectly flat or slight downhill and just barely enough throttle to maintain speed), the bike will cough and stumble, which is a lot more noticeable in the lower gears.

 

I tried balancing the TB, but that didn't help, and I think I may have made it slightly worse (I'll have to redo the TB balance). But my current theory is that TPS voltage may be slightly off, because if the TPS mistakenly reports 0% throttle, when in actuality it's slightly cracked open, then the ECU would send less fuel to the bike, leaning the mixture, and producing stumbling/misfires.

 

How does that sound? Anybody?

 

Also, I've seen several ong threads on TPS voltage, but nothing about how to adjust it, just stuff about checking it!

 

Thanks for the help.

 

Jose

[Guest ratchethack]

Jose, there's some disagreement on this, but here's my take, FWIW:

 

My bike has the exact same symptoms when the TPS voltage is set too low. I also have a PC III, an "off the shelf" map, Stucchi X-over, and FBF oval carbon cans, and stock intake, which is a similar config to what you're running.

 

Our semi-resident PC III Guru and DynoJet Rep, Todd Eagan (see GuzziTech.com), recommends a sort of "rule of thumb" setting for the TPS when a PC III is installed. This will differ from stock setups and from other methods. Simply set the TPS at 500-525 mV with the TBs connected, at idle. I suspect that if you took a current reading before moving the TPS setting, you might find a reading below this.

 

Using Todd's rule of thumb TPS setting, my bike runs so well and pulls so smoothly (gets decent mileage too) with the "off the shelf" map that I've had no need to consider a custom map.

 

I'd make certain that you have the valves set (World spec or more open by .001"-.002" each) and TBs balanced correctly first.

 

The TPS is adjusted by loosening the adjustment screws that fasten it to the TB and rotating it very slightly. A very tiny movement makes a big change.

 

Hope this helps.

 

BAA, TJM, & YMMV

[Ouiji Veck]

Then there's my seat of the pants method...

Ride the bike @ the RPM it stumbles @ ...reach down and

dial it out....( VERY small increments...)

Did this over 10,000 miles ago...the bike runs

flawlessly every where on the dial....

Also have stucci-PCIII -Mistrals....

Valves- loosey goosey...

[Mike Stewart]

Jose,

 

When you say that the throttle is at 0 percent with the throttle opened slightly, are you refering to when the bike is running and you are looking at the Powercommander table on the computor screen?

 

If that is so, then you need to zero your throttle opening through the Powercommander program. Check out the CD that came with the Powercommander and there is a section on the proceedure. Make sure the bike is warmed up and have the fast idle lever all the way off.

 

This is probably the most over looked part on installing a powercommander.

 

Also, the tps adjustment is important as well, use the figures Ratchet posted and you should be fine.

 

Mike

 

Hello all,

 

I recently added Mistral muffs and PCIII to my bike, and loaded it with the appropriate map  (Dynotune happened to have one already for Mistral muffs and stock everything else).   This is more FYI,  because I noticed the following issue before I did anything to the bike.

 

If the bike is running between 2500-3000 RPM,  AND the throttle is just baaaarely open (for example, running on perfectly flat or slight downhill and just barely enough throttle to maintain speed),  the bike will cough and stumble, which is a lot more noticeable in the lower gears.

 

I tried balancing the TB, but that didn't help, and I think I may have made it slightly worse (I'll have to redo the TB balance).   But my current theory is that TPS voltage may be slightly off,  because if the TPS mistakenly reports 0% throttle,  when in actuality it's slightly cracked open, then the ECU would send less fuel to the bike, leaning the mixture, and producing stumbling/misfires.

 

How does that sound?  Anybody?

 

Also, I've seen several ong threads on TPS voltage, but nothing about how to adjust it, just stuff about checking it!

 

Thanks for the help.

 

Jose

77796[/snapback]

[Mike Stewart]

I did a search and found this,

 

http://www.v11lemans.com/forums/index.php?...osition++sensor

 

just scroll down and there are pictures on how to set the tps.

 

Mike

[Guest jmnvhc]

Jose,

 

When you say that the throttle is at 0 percent with the throttle opened slightly, are you refering to when the bike is running and you are looking at the Powercommander table on the computor screen?

 

77808[/snapback]

 

What I meant was that I was thinking that if the TPS is slightly off, then when the thottle is slightly open, the TPS voltage is still too low for ECU to register the throttle change (so ECU thinks it's at idle).

 

I haven't zeroed out the TPS using software yet... I guess i always figured that zeroing it out was solely for the purpose of reporting the throttle position on the screen (computer side only), and not for zeroing out the throttle position input to the PC unit itself (on the bike).

 

I'll give it a shot anyway.

 

Thanks for the replies, I'll try out the suggestions and re-post.

[dlaing]

What I meant was that I was thinking that if the TPS is slightly off, then when the thottle is slightly open, the TPS voltage is still too low for ECU to register the throttle change (so ECU thinks it's at idle).

77823[/snapback]

For it to be that low, I think the bike would barely run.

It is more likely you have a lean condition from a slightly mis-set TPS.

So, the advice of the above posts is will probably get you where you need to be.

If not, I would try adding a little fuel to the problem area on the PCIII map.

Zeroing the PCIII is critical, because it tells the PCIII where to overlay the map.

The PCIII and the ECU use different markers for throttle position, but both are based on TPS voltage.

[Guest jmnvhc]

Simply set the TPS at 500-525 mV with the TBs connected, at idle.  I suspect that if you took a current reading before moving the TPS setting, you might find a reading below this. 

 

 

 

UPDATE - I measured the TPS at idle and it was at 420mv.

 

I followed ratchethack's advice by first removing the RH throttle set screw, setting the TPS to 500mv, then making a small adjustment to throttle body balance using the good ole merc sticks. (BTW, I realize I may have done some of the steps out of order, but it did the trick)

 

I took it out for a spin and it was smooooth. No more coughing/stumbling at part idle no matter how hard I tried to trigger the condition.

 

I also noticed a MUCH smoother transition from small part-open throttle to shut off. No more herky-jerky.

 

 

Thanks so much ratchethack and everyone else... me and the Guzzi are very happy now!

 

[DeBenGuzzi]

UPDATE - I measured the TPS at idle and it was at 420mv.

 

I followed ratchethack's advice by first removing the RH throttle set screw,  setting the TPS to 500mv,  then making a small adjustment to throttle body balance using the good ole merc sticks.      (BTW, I realize I may have done some of the steps out of order, but it did the trick)

 

I took it out for a spin and it was smooooth.    No more coughing/stumbling at part idle no matter how hard I tried to trigger the condition.

 

I also noticed a MUCH smoother transition from small part-open throttle to shut off.  No more herky-jerky.

Thanks so much ratchethack and everyone else... me and the Guzzi are very happy now! 

 

78021[/snapback]

I think mine might have this same problem I think I'll have it looked at when I take'er in I don't exactly have the tools or the know-how to giterdone. Thanks for the info and the updates