Off-idle stumble on a G8V that isn't cable slack

[makarushka]

UPDATE just to close this thread with some positive info: after all the tuning and adjustments that took place at the dealer for this problem, the off-idle hesitation went away also and the bike runs fine.

Just continuing to sort out a couple of issues with my wonderful 09 G8V. I mentioned (ahemm, make that "bitched about") the other one here.

So on my Griso there is this delay after you open the throttle from full closed before RPMs start to climb up and anything happens. You can wack the throttle half-open momentarily and the RPMs will not even hit 2K. You can also open the throttle VERY, VERY slowly, and you'll notice this delay still. "HA! Take that slack out of the the throttle cable, stupid!" you say. Stupid did... but it didn't help.

I noticed it right when I was picking the bike up for the first time, thought it was your typical throttle cable slack issue, and so mentioned it to the dealer right then. We made an adjustment, it SEEMED better, and away I went, all excited and sporting a stupid grin that a new Griso can give you. Long story short, the problem isn't the cable adjustment -- I have now checked and re-checked that numerous times: cannot tighten it anymore without the engine racing on lock-to-lock. The throttle cam, if you watch it as you twist the right grip from closed, is moving seemingly instantaneously, before any reaction in engine is taking place.

This delay is hard to quantify but it is enough to mess with you quite a lot -- during slow speed maneuvering especially, or getting back on throttle during deceleration -- in the twisties, for instance, of which I do at least 20 miles daily . Together with a slightly lumpy response below 4K in general as outlined in my other post, it makes the whole experience quite less of an enjoyment than expected. Have to pretty much feather the clutch with rpms well in high 3K on anything slow -- turns, etc.

QUESTIONS:

a) anyone has (or had) this on their 8V, Griso or not?
b) do you think it's purely fueling-related? I'd expect similar reports from other stock 8V owners running map 68 in that case but who knows

Any help appreciated...

 

[draidt]

Might be related to your "other" problem. You said you reset the TPS so I assume you have a VDTS or Ducatidiag setup ?

Hook up the bike to whatever you have and establish ECU - PC connection get on a screen where the TPS value is, Then SLOWLY open and hold the throttle, It takes awhile to register the change on the PC, If you get no change until you get past a certain point, Your TPS could be bad and it might explain your other condition.

The bike does not have to be running just turned on for this test.

 

[Mi_ka]

Is the TPS on these bikes of single voltage sense line type?
I encountered a yamaha R6 or so that had a double line TPS (0-5V line a, and 5-0V line b, a goes up, b goes down when opening throttle) for redundancy reasons.

 

[kmac33]

You may want to seriously consider sending Todd your ECU for re-flash. Was worth every penny for the improvement on my 4 valve Griso. From what I have read from those with 8 valves that have had it done, they are just as satisfied with the resulting improvements.

 

[Bill Hagan]

****

QUESTIONS:

a) anyone has (or had) this on their 8V, Griso or not?
b) do you think it's purely fueling-related? I'd expect similar reports from other stock 8V owners running map 68 in that case but who knows.

***

In answer to your questions ...

a. No, not on Griso.

b. DNK if "purely fueling-related," but agree with your stated expectation.

I have not gone yet to "the other post" yet, but I have to say at the outset that I find it annoying that anyone rides twisties "at least 20 miles daily."

Seriously, while, as usual, I have nary a clue as to why your Griso does that, I have some sympathy and experience with same on my Norge, especially if it's "cold to middling." There is a quite perceptible "bogging" when I turn the throttle, especially if done quickly. This is not a throttle cable issue on the Norge.

Now, that said, I have nothing like that with my Griso. While I have occasionally had a bit of an early stumble in the first few seconds after start-up, the fuel delivery is otherwise a fluid-like and there is a flawless roll on from idle to redline at a stop and on the move in all gears.

Cannot help but think yours is a mapping or similar issue. Jim Barron at Rose farm Classics did the delivery set-up and first service. I was uneasy when he hooked the software up at the 1K mark, as I did not want him to change anything. But that was an unnecessary worry, as the wonderful beast did and does run superbly.

Best wishes for you to have that soon on yours.

Bill

 

[makarushka]

Thanks everyone for your feedback; it's much appreciated!

Dan: that's what I'm thinking -- that there may be a connection. It's just that the idle stumble was there from the start, whereas the other issue SEEMs to have appeared -- or at least gotten significantly worse -- some time during the spark plug incident and running with one cylinder misfiring. I do have both software packages and will do the test as you suggest. Would be nice if the sensor wasn't buried so deep, as I'd much prefer to see the rate of voltage rising on a Fluke. On my Aprilia, there is this known tweak where a most minute position change in the TPS sensor produces a change of some 0.2millivolts. Via the regular diagnostics the computer does not see it and shows the same angle opening but it has a tremendous effect on how smoothly the bike runs, and especially in low RPM.

Kevin: absolutely, I will be doing that in the foreseeable future; I have experience with Todd's reflash on my V11 and that was a single most radical and useful change for that bike's fueling, no doubt. I want to first make sure, however, that the machine is mechanically sound first and that I don't start applying fixes that may not eliminate the root cause problem.

Bill: Yes, I am lucky to have a most wonderful commute that I actually look forward to every day and am able to ride it pretty much all year round. On the other hand, I have very little time outside of this to do leisure riding. I rarely ride on a weekend, for example, probably no more than once a month... Do you feel sorry for me now instead? Come on, have a heart ) I wish I had a good, experienced and enthusiastic Guzzi dealer somewhere around but that does not seem to be the case. There are a couple of great Guzzi mechanics that I know but these are people very well versed with previous generations of Guzzis and not necessarily so well-versed with the particulars of the new 8V engines. I find that, for instance, everyone seems to want to tune the 8V the same way they'd tune the older big block, and that only one bypass screw needs to be open is news to them and causes head scratching in disbelief. Plus on a new bike you really want to sort out the quirks with dealer involvement so that anything "chronic", so to speak, is known up the chain and perhaps improved upon in future production.

Again, thank you all for your input!