MotoZA
Tuned and Synch'ed
Hi all,
Time for remote diagnostics/ideas/hints again, please...
My Stelvio NTX (MY2012) runs like a champ as soon as it's on the move, the engine runs smoothly, no surging, dropping, nothing like that. Basically, the bike pulls like train once on the go. BUT, as soon as the rev's drop to below about 2000 rpm (for example when stopping or at parking lot speeds), she will sometimes stall, or idle very rough, other times she'll idle fine. Very intermittent behaviour.
Mostly, the problem is that the bike won't idle constantly (cold or hot), the engine rev's surges up and down (between 1200 and 1600 rpm), sometimes it drops (misfires), I can both hear and feel this. I can see the stepper motor trying its best to get a constant idle (if I watch the throttle body tie-rod).
My throttle bodies are synced perfectly (to within 0.5 cm Hg with my CarbMate at 3500 rpm). TPS is 4.8 deg. I also know it cannot be unbalanced throttle bodies or incorrect TPS, since the bike runs so well once on the move. Throttle bodies are clean on the inside. The bike starts very easily. Spark plug wires/cords are fastened, I have the NGK plug caps installed. No ECU or Dashboard errors. I've never touched the sacred screw or tie-rod, and they've never been touched (the sacred screw has a small tack weld that is still intact; I assume this is done at the factory).
I've run different fuel maps (for other reasons, not sort out to idling), it makes no difference (I don't expect that it should), but even with the stock map and everything back to stock, I have the same idling issues.
Here is a confession of sorts that may point to my problem, both my air bleeds screws are closed. Why? Since the bike struggles to idle, the vacuum changes form left to right, so I have no idea which air bleed to adjust. I remember long ago when I first synced the throttle bodies, that the one air bleed was turned out quite a bit (the right hand throttle body), but at that stage I turned it in to get balance at idle. I also used to idle quite high (at about 1600 rpm). At the time I wanted to get things "as they should be".
In the past the bike used to idle OK (although high), but then it used to surge whilst on the go. I have the surging sorted now, but not the idling.
Any advice or ideas on what I should try next? Could it in fact be coil or spark plug (and caps or wires) related, or perhaps the stepper motor? I think it is the air bleed screw(s), but I'm not a trained mechanic and don't have much experience, so cannot say for sure. Also, I live a 1000 miles (literally) from the nearest Guzzi dealer, so that's not an option...
Thanks,
William
Time for remote diagnostics/ideas/hints again, please...
My Stelvio NTX (MY2012) runs like a champ as soon as it's on the move, the engine runs smoothly, no surging, dropping, nothing like that. Basically, the bike pulls like train once on the go. BUT, as soon as the rev's drop to below about 2000 rpm (for example when stopping or at parking lot speeds), she will sometimes stall, or idle very rough, other times she'll idle fine. Very intermittent behaviour.
Mostly, the problem is that the bike won't idle constantly (cold or hot), the engine rev's surges up and down (between 1200 and 1600 rpm), sometimes it drops (misfires), I can both hear and feel this. I can see the stepper motor trying its best to get a constant idle (if I watch the throttle body tie-rod).
My throttle bodies are synced perfectly (to within 0.5 cm Hg with my CarbMate at 3500 rpm). TPS is 4.8 deg. I also know it cannot be unbalanced throttle bodies or incorrect TPS, since the bike runs so well once on the move. Throttle bodies are clean on the inside. The bike starts very easily. Spark plug wires/cords are fastened, I have the NGK plug caps installed. No ECU or Dashboard errors. I've never touched the sacred screw or tie-rod, and they've never been touched (the sacred screw has a small tack weld that is still intact; I assume this is done at the factory).
I've run different fuel maps (for other reasons, not sort out to idling), it makes no difference (I don't expect that it should), but even with the stock map and everything back to stock, I have the same idling issues.
Here is a confession of sorts that may point to my problem, both my air bleeds screws are closed. Why? Since the bike struggles to idle, the vacuum changes form left to right, so I have no idea which air bleed to adjust. I remember long ago when I first synced the throttle bodies, that the one air bleed was turned out quite a bit (the right hand throttle body), but at that stage I turned it in to get balance at idle. I also used to idle quite high (at about 1600 rpm). At the time I wanted to get things "as they should be".
In the past the bike used to idle OK (although high), but then it used to surge whilst on the go. I have the surging sorted now, but not the idling.
Any advice or ideas on what I should try next? Could it in fact be coil or spark plug (and caps or wires) related, or perhaps the stepper motor? I think it is the air bleed screw(s), but I'm not a trained mechanic and don't have much experience, so cannot say for sure. Also, I live a 1000 miles (literally) from the nearest Guzzi dealer, so that's not an option...
Thanks,
William