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breva stumbles and stalls

NOLAGuzzi

Cruisin' Guzzisti
Joined
Dec 5, 2008
Messages
102
My 04 750 breva has been acting up. It starts and idles fine but while riding anywhere past about 4 K RPM it stumbles and dies when I back off the throttle. Then starts right back up when I hit the starter. This started happening out of the blue three days ago.

So far I have drained the fuel tank and refilled w/ different gas, pulled and replaced the plugs, looked at the rev sensor (it was nice and clean), looked for loose connections or hoses that might interfere with the throttle opening and closing and reset the TPS with the VDST. No change with the bike.

While the VDST was plugged in I looked for DTC error codes, current or historic, and there were none. However when I bring up the system status window I get a red flag on the TPS trimmer OK.

Any advice on how to proceed would be appreciated.

Thanks.
 
When you changed the plugs, did you also adjust the gap?
I've found my Breva to very sensitive to the gap closure, and 0,65 mm to be correct. New plugs are usually quite different to that.

Also, check the coil. I know the VDSTS do have that feature, but there might be something happening when the coil is getting hot - or would the failure occur immediately after taking off, also?

RED flag? My memory's probably wrong as mostly, but shouldn't it be green?

Ooh, one thing more. I haven't got a clue if it would work, but as everything is controlled by the ECU, you could try to disconnect the battery for a while, to reset some kind of memory flaw. Might be worthless, but it's free.
 
Interesting that there is a red flag on the trimmer. Trim on the 15RC is in relation to Lambda voltage. That is, as the lambda voltage changes, so does the trim value. With the VDSTS connected and engine warm, see if the lambda voltage is changing (should be rapidly, but commonly not). If no voltage changes, replace the lambda sensor.
 
Thanks for the replies.
I checked the voltage on the lambda sensor and it changes, but certainly not rapidly. I just ordered a new lambda sensor and when I put it in I will check the spark plug gaps too. Hopefully that will resolve the tps trimmer error and the stalling. If the new sensor does not sort things out I will pull the tank and look into the fuel filter and coils.
 
Re:breva stumbles and stalls UPDATE

So i got a new lambda sensor and a new set o plugs and the stalling and stumbling has stopped. HOORAY! I put a couple hundred miles on the bike w/ new sensor and my efi light did not do it's little on and off routine either. The bike runs better than it ever has.

But...
the TPS trimmer error is still displayed when I look at the system status. My lambda voltage fluctuates rapidly now and the open circut lambda error is gone so I assume that all is well with the sensor. Like I said the bike runs very well now so I am just not going to plug in the VDST and not worry about the TPS trim error.
 
Re:breva stumbles and stalls UPDATE

I would ignore the trim error as well. I think there are ghosts in some of these ECUs. A friends Jackal (1.5M system) always reports the TPS shorted to ground, but the TPS voltages are correct and the bike runs fine.

Have you done a clear DTC yet to see if it returns?
 
Re:breva stumbles and stalls UPDATE

You are right, clearing the error history would be a good idea. Next time I plug in the cable I will do that. Hopefully it will be a while.
 
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