phazer rough start

[faithfullyamaha]

So I fixed a few things on the phazer today and when I went to start it up I got the code 22. I plugged the sensor in that I had forgotten and when I went to start it up again it fired up after only one revolution. This has never happened before and I certainly don't mind it. Maybe it had something to do with the intake air temp sensor? Any thoughts?

 

[Voda2000]

I wonder if with the intake temperature sensor disconnected the computer added more fuel. Then when you restarted there was already extra fuel in the cylinders?

 

[faithfullyamaha]

At first that's what I thought. But then I was thinking the engine still started and ran while the sensor was disconnected. So it would have burned off any extra fuel. I wonder if the sensor read that the air was colder than it was could it have fooled the ecu into changing the a/f ratio? Maybe the whole thing was a coincidence but I'll be checking tomorrow to see how it starts up.

 

[cannondale27]

That is interesting. If you find that it does assist starting would be easy enough to add a valve in those hoses. Great job!

 

[faithfullyamaha]

The intake air temp sensor actually is the one next to the intake air pressure sensors which are the ones with the hoses. This sensor just has a little probe that sticks into the air box. But instead of a valve a cutoff switch would work. That's if this is the reason for my abnormally easy startup

 

[faithfullyamaha]

The intake air temp sensor actually is the one next to the intake air pressure sensors which are the ones with the hoses. This sensor just has a little probe that sticks into the air box. But instead of a valve a cutoff switch would work. That's if this is the reason for my abnormally easy startup

I've done some more research and it is possible to switch the sensor but if extra wiring is added in for a switch it could alter the resistance of the sensor and make the engine run rich or lean even when not switched off. I'll be trying a couple things tomorrow hopefully I stumbled onto something really useful.

 

[faithfullyamaha]

I wonder if with the intake temperature sensor disconnected the computer added more fuel. Then when you restarted there was already extra fuel in the cylinders?

Not to comment on my own post too many times but Voda2000 would be right because when the sensor was plugged back in it started quick which would mean either the ecu was still pumping in fuel like it was disconnected or there was excess fuel in the cylinders. Hopefully someone smarter than me can shine some light on the subject.

 

[Voda2000]

I don't know how Yamaha configured the ecu but based on it being an open loop system here is my thought.

The ecu looks at air temp and pressure (and throttle position) and sets a a/f ratio based on a predefined tables. When the computer "loses" a sensor it would be programmed to go to the most conservative setting, like "limp mode" on a new car. For the Phazer, I assume that if the ecu the lost of temperature it would assume it was very cold and make the mix very rich to minimize the risk to the motor.

My guess is that your sled loaded up on fuel and that's why it restarted so quickly. I'd be careful using this idea to try and start it because you may end up fowling the plugs. Plus you would have to trick the sled before you shut it down to get the extra fuel in the cylinders and this could result in wall wash.

You also are right about the extra resistance messing up things. There used to be products on eBay that claimed to add horsepower simple by plugging in a little black box inline with a harness. A lot of those are just resistors that trick the computer into dumping in more fuel and done really make any more power.