Cold idle issue on 1500FI

[T-man]

Here is one that has developed over the last year or so. As the temps cool in fall, cold start idle gets rough and slow. Specifically, after start, the ECU is activating the ISCs properly and a fast idle is initially present. The fast idle exists for about 15 seconds or so, then the idle speed drops quickly to about 900 RPM. If left to idle, the idle speed drops further and the engine begins to lope and miss, running rich. Sounds cool, like running a cam, but it's not right. If left long enough, the engine has stalled. Usually I ride off by then and the engine response above idle is fine, and after it warms a little, it idles fine, albeit still sounds a little rich.

There are no trouble codes in the ECU (been checked) and no FI light has ever come on.

I suspect the air temp sensor or water temp sensor is going bad but not bad enough to be out of range of the ECU to set a trouble code.

Well, what do ya think? I am thinking of putting a resistor in the air temp socket and try a cold start and trick the ECU to think it has 90 degree outside air and see what happens.

The only thing that bugs me is that I would think if the water temp sensor is good that it and the ECU would keep RPM up until water temp is higher. Maybe both are going south?

T-man

[larrycavan]

When the idle drops to 900, what happens if you take the engine off fast idle? Does it stall?

Larry C

[T-man]

Originally Posted by larrycavan

When the idle drops to 900, what happens if you take the engine off fast idle? Does it stall?

Larry C

The ECU controls the idle speed. I don't do anything to start the bike cold (or hot) except to turn the key 'on' and push the starter button. The ECU reduces idle speed automatically.

[Paco]

I dont know how much the sensors are? but if they not
expensive try replacing one at a time and see what happens.
If not, can you take the sensor to the shop and have them
check them out. Thats the only thing I can come up with.

[bross]

Mine sorta does a similar thing but, dies much sooner. Bike fires immediately runs for about 3-4 seconds, then dies. Fires right up the second time and runs and idles normally. I did notice when I was just running the bike after changing the oil on Sat that the idle kept dropping. I was just running the bike to distribute the fresh oil and fuel stabilizer before putting away for the winter so I just held the throttle and blipped it. Didn't think twice about it, but now I'll have to watch for that in the spring. Sorry I don't have any ideas right now.

[T-man]

Originally Posted by Paco

I dont know how much the sensors are? but if they not
expensive try replacing one at a time and see what happens.
If not, can you take the sensor to the shop and have them
check them out. Thats the only thing I can come up with.

The air temp and water temp sensors are about $33 or so from Ron Ayers, less shipping and my local shop charges $70/hr...plus I am a DIY guy <G>. I hate to 'trial and error' it but might have to...I could pull them and put them in a pot of oil with a thermometer (per the service manual) and measure resistance...lot of messing around...think I'll go to Radio Shack and get a resistor and try that approach first unless someone out there has done this before and can lead me.

Where's QKENUF4U when I need him??

[T-man]

Originally Posted by bross

Mine sorta does a similar thing but, dies much sooner. Bike fires immediately runs for about 3-4 seconds, then dies. Fires right up the second time and runs and idles normally. I did notice when I was just running the bike after changing the oil on Sat that the idle kept dropping. I was just running the bike to distribute the fresh oil and fuel stabilizer before putting away for the winter so I just held the throttle and blipped it. Didn't think twice about it, but now I'll have to watch for that in the spring. Sorry I don't have any ideas right now.

Yours sounds maybe lean rather than rich...mine chugs along very rich acting, if I throw her in gear and pull off, she'll pull right out...if it were lean, it would die. Even after it's full hot, idle has a slight lope, different than it used to be. I've been ignoring it for about a year waiting till something when totally kaflooey (tech term).

[bross]

Originally Posted by T-man

Yours sounds maybe lean rather than rich...mine chugs along very rich acting, if I throw her in gear and pull off, she'll pull right out...if it were lean, it would die. Even after it's full hot, idle has a slight lope, different than it used to be. I've been ignoring it for about a year waiting till something when totally kaflooey (tech term).

Good possibility on the lean part as I'm totally stock, but I just did the resistor mod about a week before I put the bike away, so that should have richened it up a bit. I used a 570ohm resister. We'll have to wait till spring to test it. BTW Winter sucks!

[larrycavan]

T-Man,

You might already have this link but I'll toss it to you just in case.http://www.gadgetjq.com/fi_fuelsystem.htm

FWIW, you're definitely up to the task of sorting out the problem, based on what I've read in your posts. On the old FI GP11's, if I recall correctly, grounding the air temp sensor told the ECU to go full rich. Not sure if it's the same on your VN. If that's the case, just unhooking the wire and trying a cold start might point you in a direction..

Good Luck,

Larry C

[T-man]

Originally Posted by larrycavan

T-Man,

You might already have this link but I'll toss it to you just in case.http://www.gadgetjq.com/fi_fuelsystem.htm

FWIW, you're definitely up to the task of sorting out the problem, based on what I've read in your posts. On the old FI GP11's, if I recall correctly, grounding the air temp sensor told the ECU to go full rich. Not sure if it's the same on your VN. If that's the case, just unhooking the wire and trying a cold start might point you in a direction..

Good Luck,

Larry C

Hey Larry, thanks for the words and link.

On the Kaw ECU, the resistance read by the ECU is out of range, the ECU will set a trouble code and it will assume a median value for the purposes of keeping the bike running, so I can't unplug or ground the connector without setting the dreaded FI light.

Thanks for the support!

[larrycavan]

T-man,

Tough call. It could be either sensor. It could even be ECU [though I'd pray it's not]. I mention CPU because one time I had GP11 that would run fine for days at at time, then out of nowhere it starts missing..not a steady miss, just a cough and cleard itself. It might do it 5 or 6 times in a mile and then maybe not do it again for a couple of days...you never knew when it was going to act up. Anyway the customer would come in with it and of course it always ran fine then. Ultimately, it was the CPU that was bad. Not bad in terms of not running..just bad in terms of it would cause the miss on occasion.

Larry C