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VN1500 Fi cold idle problem

2105 Views 4 Replies 2 Participants Last post by  QKENUF4U
My 2001 Vulcan 1500 Fi always starts right off and idles well hot. The issue is that the colder the morning, it goes like this: after start, the engine will idle at an elevated speed and after about 10 seconds or so, will idle down to a very slow rpm and begin to miss and stumble. Sounds like a vintage tractor hitting about every 10 revs. I have to crack the throttle a little or the engine will finally stall. After it warms up, it idles fine. Runs above idle fine.
On a possibly related note, I seem to be getting a little lower overall gas mileage (from 48-50 mpg to 40-45). No other symptoms are noted, runs strong and smooth when hot.
These symptoms seem to indicate the ISC valves are working as well as the temperature sensor.
Anybody run into this before?
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Hopefully I am, but what has me a little bugged is that the FI light has not come on indicating a sensor out of range. One would think that if the sensor is crapping out that the ECU would pick it up. Hmm, wonder if a sensor is giving a false signal and ECU just thinks it's okay??
I did a little more diagnosis - pulled out the ECU, grounded terminal #37 to put it into diagnostic mode and there were no stored trouble codes. Now I am :?: ... so, ran it at idle awhile until it warmed up, shut off the engine, and pulled the plugs. They had a bit of soot on them. Expected them to be black from just running at idle but the soot was a little fluffy and wiped off readily.
Next, I hooked my laptop up to the PCIII and got the map from PCIII and started the bike. It idled around 900 or so and the throttle position indicated 2-3%. The map indicated the PCIII was adding 8 points enrichment at the 2% and 1000 RPM. So I went in and zeroed the settings at 2% and 5% at 1000 RPM since the algorithm uses a smoothing formula, I believe between the points. Lower revs were already set at 0. I want to try this out and see if things improve.

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