Bad idle with cold ambient temps

[quixitoc]

Got an 04 FZ6 and have issues with idling when the outside temp is cooler than ~80 degrees Fahrenheit. After about 10-20 minutes of riding, the idle goes up by 500-1000 rpm and stays there. After another 10-20 minutes (sometimes longer) it drops down to about 800-900 rpm, which sometimes causes it to stall when coming to a stop. One thing I’ve noticed is the smell of the exhaust changes when dropping low, not sure if it goes lean or rich because I don’t have much mechanical experience, but it does smell like those gas go karts do. The bike also sounds “hollow”.

I’ve checked the TPS sensor using diag mode and it reads as normal, and also the air temp sensor reads as expected, gives the outside temp for a bit and then reads a bit higher when the bike warms up. Any help?

 

[Motogiro]

See how it behaves by warming up the bike and adjust the RPM to about 1100.

 

[Gary in NJ]

Do you notice any swings in the water temperature gauge when the idle anomaly happens?

 

[quixitoc]

Do you notice any swings in the water temperature gauge when the idle anomaly happens?

No, it stays between 2-3 bars when riding depending on the outside temp, and it goes up to 4 if it's warm enough when I'm standing still. Seems normal as far as I can tell

 

[Gary in NJ]

You may have a faulty Air Cut-Off Valve, or the signal from the ECU to the valve may be intermittent due to corrosion in a connector. It would explain the fuel smell as well. From the FSM:

AIR CUT-OFF VALVE
The air cut-off valve is controlled by the signals
from the ECU in accordance with the combus-
tion conditions. Ordinarily, the air cut-off valve
opens to allow the air to flow during idle and
closes to cut-off the flow when the motorcycle is
being driven. However, if the coolant tempera-
ture is below the specified value, the air cut-off
valve remains open and allows the air to flow
into the exhaust pipe until the temperature be-
comes higher than the specified value.

 

[quixitoc]

You may have a faulty Air Cut-Off Valve, or the signal from the ECU to the valve may be intermittent due to corrosion in a connector. It would explain the fuel smell as well. From the FSM:

AIR CUT-OFF VALVE
The air cut-off valve is controlled by the signals
from the ECU in accordance with the combus-
tion conditions. Ordinarily, the air cut-off valve
opens to allow the air to flow during idle and
closes to cut-off the flow when the motorcycle is
being driven. However, if the coolant tempera-
ture is below the specified value, the air cut-off
valve remains open and allows the air to flow
into the exhaust pipe until the temperature be-
comes higher than the specified value.

Thanks, I'll check out the connector to that tomorrow. If the connector is fine, is there any method to test the valve itself? The FSM just says to replace if you see any visible damage.

See how it behaves by warming up the bike and adjust the RPM to about 1100.

I'll check that out next time I ride, I have the idle set to about 1300 in normal conditions to prevent it from stalling instantly when it drops low.

 

[quixitoc]

See how it behaves by warming up the bike and adjust the RPM to about 1100.

Ok, just did that and now warm idle is about 1100-1200 rpm down from 1300-1400. I had to turn that idle adjust screw a lot, but it seemed to fix the high idle issue.
However, the low idle thing still happens after about 30 minutes to an hour. Haven't been able to check the air cut-off valve yet, and the strong gas smell still remains when the idle drops.