Gen2 start question

old1959

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Thoughts and comments wanted. Background: My 2017 non ES with 35k miles which I checked the valves, changed air filter, plugs at 26k has occasionally been hard to start when cold. I live in Texas so this isn’t often. Also, the bike has stalled three times in the almost two years I have owned it; did the throttle syncing per what I learned on the forum. Bike delivers great gas mileage being mostly over 50mpg. Bike runs well with no check engine light coming on. Oh, and valves were in spec.

Last Saturday, which was cold, high 40’s to low 60’s the bike surprised me with starting up quickly in the morning. Usually cranks a bit when cold. However, after a lengthy lunch stop, bike cooled down and temps were mid 50’s the bike required some cranking and started with just a slight twist of throttle. The rest of the day all but one time the bike immediately started; one time took a few extra seconds. Normally I ride in warmer temperatures and bike starts quickly.

My thoughts and observations. If this bike had a carb, I would be tempted to richen the pilot jet and raised the idle just ever so slightly. I think it exhibits a lean condition. But the bike is fuel injected and knows the outside air temperature so should adjust fuel mixture to temperature. So I started thinking . Which led me to further observations...

The temperature read out on the dash. While riding out riding and passing businesses with thermometers on their business signs last Saturday, and not stopped in heavy traffic, my dash temperature reads eight to eleven degrees higher. Also, checking the cold bike in the garage since I’ve been home the dash temperature is reading approximately ten degrees warmer than garage or outside thermometer. Hmmm. From further research, I’ve discovered the ECU is using this same temperature data to determine ambient temperature and set fuel mixture. My hypothesis: I believe this temperature difference is what is causing the bike to be slightly lean since the ECU is thinking temperature is warmer than it actually is. Comments?

Note: What got me thinking this direction is how the Booster Plug works as described on their website. The device modifies the temperature reading to the ECU to read 20 to 30 degrees lower which causes the ECU to use a richer mixture.

Thank you and would enjoy hearing some thoughts.
 

EricV

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On both my 2012 Gen I and 2015 Gen II Super Tens, the ambient air temp would be correct when turned on in the garage prior to running. During riding, at some temps and conditions the temp would be spot on, other times and conditions might see higher or lower temps, but typically it was higher than actual. This all makes sense in terms of the sensor being inside the air box.

From your descriptions, I would suggest that your intake air temp sensor is faulty. It should read accurate on a cold bike, key on in the garage, unless you have a very drafty garage where wind/air currents would impact a wall thermometer but the sensor inside the air box would be sheltered.

If you're still under YES warranty, take it to the dealer and have them check the sensor. If you have a FSM, there is likely a procedure for testing the intake temp sensor, follow that and see what the result is.
 

Longdog Cymru

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This is something that I have found on my 2017 Gen 2 bike. If I compare the outside air temperature displayed on my bike to my car or to my friend’s bikes, then mine is showing 4-5 degrees C warmer than their temperature display.
 

EricV

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This is something that I have found on my 2017 Gen 2 bike. If I compare the outside air temperature displayed on my bike to my car or to my friend’s bikes, then mine is showing 4-5 degrees C warmer than their temperature display.
And while riding, that is to be expected. The air box sits right on top of the engine and gets heated by it to varying degrees, (pun intended). The cars and some bikes, (BMWs), have separate external air temp sensors and usually are more accurate.
 

Jlq1969

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I believe that if you do not want to have cold and hot start problems, never, but never release the start button until it really starts. If you release that button before and try again .... the problems begin
 

MattR

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I always start my 17 gen 2 with no throttle at all including down to 0 c.
However, I also always plug it into my optimate every time I put it away at night.
Sometimes it seems to crank slowly but it never fails to start.


Sent from my iPhone using Tapatalk
 

old1959

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FYI. Bike always starts. And the difficulty of starting is a random occurrence. Also, the temperature reading will rise slightly if sitting traffic or not moving but so does my car, Subaru, temperature. However, at highway speeds both bike and car come down. I’m just noticing the S10 is consistently high. Faulty sensor maybe?
 

Checkswrecks

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The temp readout is actually sharing the input for the ECU so is in the airbox above the engine. No surprise that it's typically warmer than ambient. Not going to change.

Look up some of the threads about balancing the throttle bodies and that may help both the throttle feel and the occasional hard start.
 

Jlq1969

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Probably, the sensor of your Subaru, is in the front grid or in some side mirror and is to measure the outside temperature. The one of the S10 is inside the air box, above the engine, the air intake looks back, it will always receive hot air, and apart from all this, somewhere in the manual, it clarifies that the temperature shown on the board does not It is the “outside”, it is the “inside” of the filter box
 

dell835

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Probably, the sensor of your Subaru, is in the front grid or in some side mirror and is to measure the outside temperature. The one of the S10 is inside the air box, above the engine, the air intake looks back, it will always receive hot air, and apart from all this, somewhere in the manual, it clarifies that the temperature shown on the board does not It is the “outside”, it is the “inside” of the filter box
Exactly-Subaru sensor is in the lower part of the grill. It does read high if
the car sits still for a while but drops down immediately when it gets some air movement.
 

old1959

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Agree with comments. But note my earlier comments that temperature readout is high on the bike cold; hasn’t been ridden in a few days. So engine heat won’t have an impact in this situation.

I have factory manual and below is how to test sensor which I’ll do once I get a multimete; mine broke a while back and haven’t replaced it yet. Manual gives a range for resistance checks. Of course, I know my sensor hasnt failed but I suspect it is a little off; maybe at the limit of the acceptable range.
3C9EE537-36FE-412B-B007-A0764E3F54D4.jpeg
 

Longdog Cymru

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Probably, the sensor of your Subaru, is in the front grid or in some side mirror and is to measure the outside temperature. The one of the S10 is inside the air box, above the engine, the air intake looks back, it will always receive hot air, and apart from all this, somewhere in the manual, it clarifies that the temperature shown on the board does not It is the “outside”, it is the “inside” of the filter box
I agree that the air box is above the engine, but if you are travelling at say, 60 mph with an outside air temperature of, let’s say 10 degrees F, then with wind chill, the air entering the air box will be -19 degrees F.
Take a look at the link below.

https://en.wikipedia.org/wiki/Wind_chill#/media/File:Wind_chill.png

Now I don’t think that air will be in the air box too long before it is ingested by the engine, so I think there must be a calibration for that sensor to compensate for this. Maybe, just maybe, the calibration could be out a little, or the sensor may not be mounted far enough into the airstream or there could be some obstruction to the air stream such as a leaf or dead bug. Now I am speaking speculatively here but I think there is room for discussion and I think that there may just be some production tolerance making a few degrees difference between bikes.
 

Jlq1969

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Agree with comments. But note my earlier comments that temperature readout is high on the bike cold; hasn’t been ridden in a few days. So engine heat won’t have an impact in this situation.

I have factory manual and below is how to test sensor which I’ll do once I get a multimete; mine broke a while back and haven’t replaced it yet. Manual gives a range for resistance checks. Of course, I know my sensor hasnt failed but I suspect it is a little off; maybe at the limit of the acceptable range.
View attachment 62554
This is the S10 air temperature sensor. Instead of measuring the resistance, why do not you take it out, put it together with the meter you have in the garage, and apply air with the hair dryer, cold / heat .... and you get out the doubt, and you don't spend on a multimeter just for this
EC56431D-068C-407D-8A87-609A8F40A4C5.jpeg
 

Jlq1969

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I agree that the air box is above the engine, but if you are travelling at say, 60 mph with an outside air temperature of, let’s say 10 degrees F, then with wind chill, the air entering the air box will be -19 degrees F.
Take a look at the link below.

https://en.wikipedia.org/wiki/Wind_chill#/media/File:Wind_chill.png

Now I don’t think that air will be in the air box too long before it is ingested by the engine, so I think there must be a calibration for that sensor to compensate for this. Maybe, just maybe, the calibration could be out a little, or the sensor may not be mounted far enough into the airstream or there could be some obstruction to the air stream such as a leaf or dead bug. Now I am speaking speculatively here but I think there is room for discussion and I think that there may just be some production tolerance making a few degrees difference between bikes.
Probably, to avoid that, it is that the air inlet in the filter box, looks back, then the air that enters, is only the one sucked by the pistons.
 

WJBertrand

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I agree that the air box is above the engine, but if you are travelling at say, 60 mph with an outside air temperature of, let’s say 10 degrees F, then with wind chill, the air entering the air box will be -19 degrees F.
Take a look at the link below.
Wind chill is irrelevant to inanimate objects, it's only applicable to living things.

My 2015 had periodic hard / slow starts that got worse and worse. By the time the battery was 4 years old I was loosing confidence in it. I installed a Scorpion LiFePO4 battery with a claimed 387 CCA one year ago and have not had a hard or slow start since.
 
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old1959

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Another data point. I just checked temperatures... Bike 62. Thermometer 57. Subaru is 59. All very close. I don’t think the sensor is bad but maybe the tolerance on it is slightly such that it reads a bit high; maybe just high enough to cause the occasional hard start.
 

Jlq1969

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Another data point. I just checked temperatures... Bike 62. Thermometer 57. Subaru is 59. All very close. I don’t think the sensor is bad but maybe the tolerance on it is slightly such that it reads a bit high; maybe just high enough to cause the occasional hard start.
The spark plugs? .... with 35k miles, will they be there to change them? The clearance will have increased enough to delay the spark ?, And this causes some decompression. If there is a moment where a spark plug problem is noticed, it is at startup
 
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