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Discussion Starter · #1 · (Edited)
Hello all, I was wondering if I could get a little assistance with something I've been troubleshooting with my '04 Daytona 955i.

I am of the opinion that there is something wrong with the IAC. Frequently when I try and start the bike, it will fire up but then die immediately. This can happen several times in a row,once it happened like 8 times before the engine begrudgingly and quite roughly stayed on. However, every once in awhile it will fire up right to fast idle and everything is fine, but most it doesn't. 99% of the time a cold startup is at low idle, about 800rpm.

So today I decided to take a closer look at the IAC and its hoses. I removed the stepper motor to check the resistance at the pins and they are all within spec. The vacuums line all look good as well. So next I decided to hook it back up and give it power to see if it was moving up and down.

Now here is where I need a hand. From the looks of how its put together, when the stepper motor is compressed (moves down) it is allowing air to travel down the hoses. When the stepper motor is extended (moves up) it will limit, or block air from traveling down the hoses. Based on what I understand from working on cars, when you block the air you're effectively choking the engine. Therefore, I would think that on a cold start up, that the stepper motor would be fully extended (up).

However this is not what happens when I turn the key. With the sensor at the top of the air box reconnected when I switch the key to the on position the stepper motor compresses, thus allowing more air to travel. When I shut the key off the stepper motor seem to do a self test and extends all the way out until it can't anymore then resets itself back in a compressed position.

My question is, shouldn't the stepper motor full extend and block the hoses when the ignition is on for a cold startup?

Thank you in advance, your help is greatly appreciated :)
 

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activeseven, From my experiance with fuel injection systems the ECU performs the 'choke' function on a cold engine by increasing the injector duty cycle, if this is what you're thinking.

The big problem for cold starts in the 10% ethanol gas. My '04 became difficult to start when the change over occured in my area. From what I've learned the ethanol percentage is maxed at 10%, but sometimes is mixed at a smaller percentage...when my '04 cold starts easily I'm guessing the percentage is less than 10%. The long term fuel trim can have the CO percentage increased for easier starts, which I haven't bothered with.

Brad
 

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Discussion Starter · #3 · (Edited)
I see, so the stepper motor is functioning properly then? I seem to recall reading something on these boards earlier about the 10% ethanol issue. There is a way to have the dealer correct this isn't there?

edit:
Just did a quick search on the CO issue, you and I have had this conversation before :)
So I just tell the dealer to raise the long term CO percentage raised? Any idea what it should be raised to? 10%?
 

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activeseven, I don't know positively as I haven't done it, but it'll be more like to 3-3.5%. IIRC, my '04 is just under 3% CO according to the dealer's tool.

Brad
 

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CO level is set automatically on your bike with the O2 sensor. Any adjustments will bring it back to its norm.
The CO level used to be adjusted manually on the pre-2002 bikes because there was no O2 sensor

Idle control:
The throttle bodies normally receive air through the large main open port at the top; the volume of air is controlled by the throttle plates which are directly operated by the throttle control.
At idle those plates are completely closed. There is a small volume of air however, that is directed through a bypass orifice in the throttle body. That orifice is fixed but the volume of air that is directed is controlled by the Idle Air Control valve. That valve receives its direction from the ECM - the ECM measures the engine RPM and will instruct the ISCV to introduce more or less air to maintain the correct speed per the preset value in its 'look-up table'
There are different values of preset value depending on the engine (coolant) temperature so the set point will change according to that.

The most common problems associated with idle control are usually that it will idle fast - this is because more air translates to higher rpm and the common failure is a leak (whether through cracked hoses or bad TB gasket or whatever) - the ECM detects the higher speed and attempts to 'shut down' the ISCV to reduce the speed; however if the air is entering the system beyond the valve, it is powerless to get the speed down, even if the valve virtually closes.

If the idle speed is low however, that says that the ISCV should be commanded to open up, yet it still can't get the engine speed up.
Now that could be a problem with the ISCV or a blockage of the intake to it, however that is less likely. In the instance of low engine speed, I'd be looking more to the fuelling or ignition side of things.

First off I'd pull/replace the plugs - check for fouling and also check the igntion coils.
 

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Discussion Starter · #6 ·
First off I'd pull/replace the plugs - check for fouling and also check the igntion coils.
Thanks DEcosse, the plugs are new so I'll look in the service manual for a way to test the coils tonight. While I'm at it, I'll check the O2 sensor as well just to be sure.

Do you still think I should take it to the dealer and have the long term fuel trims CO% looked at?
 

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Discussion Starter · #8 ·
Thanks DEcosse, I actually did that already as well before I checked the IAC

Regarding the ignition coils though, I just tested the resistance on all the coils and they are showing 1.4 - 1.5 the service manuals say they should be .8 though. Is this an "acceptable" deviance? Or should I buy new coils?
 

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Discussion Starter · #11 ·
Ok thanks DEcosse, I figured it was fine since they all read the same, I just wanted to make sure. Everything seems to be fine mechanically with the bike.

I'm getting the bike tuned this weekend, I'll let you all know how it turns out :)
 
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