Cold & Hot Start Issues

My new to me 2005 Swing has a bit of a temperament. Sometimes it starts as it should, but most of the time on a cold start if I just start and with no throttle, it will start and the idle will be high, them it will slowly drop the idle and die after a about 10-15 seconds, sometimes it will keep running, but barely. If I notice this happening, I can bring the idle up to about 1700-1900rpm and give the throttle a quick blip and it will go to the cold start high idle and then idle down as it should, and run fine from there.

On hot starts, most of the time it will stat and almost immediately die, but if I give it about 1/8 to 1/4 throttle it will start and run fine.

I have replace the fuel pressure regulator and spark plugs, air filter is clean, gas is fresh and ran some fuel injector cleaner through a couple tanks.  Have run it on the highway for miles to try and clean things out.

To me it seems like it might be some sort of sensor that is malfunctioning I am not getting any errors on the dash.

Any thoughts on what might be causing this issue?

Thanks in advance for all your expertise.

Chad

Hi Thmp Thmp.

Have you tried the Self Diagnostic Procedure as listed in the workshop manual ? under PGM-F1(programmed fuel injection) systems 02-07.

Hope this helps.

Be safe, be seen!

I have not, as a matter of fact I didn’t realize there was a self diagnostic feature. I will look into this.

Cracked vacuum line?

Welp, did the self diagnostic and there were no codes or codes in memory.
Oh yeah, forgot to mention that I replaced all of the vacuum lines when I installed the new FPR.
It’s a strange one.
Thanks for the suggestions so far, I am open to hearing any other idea the forum comes up with.

Could this be electrical? rectum fryer? weak coil? , bad plug leads?

Loosemarbles wrote:

Could this be electrical? rectum fryer? weak coil? , bad plug leads?

What exactly is a rectum fryer, is it Honda's more powerful version of a heated seat?

It's an old-school term for 'rectifier'.

Make sure the brass air-screws on each throttle body are open a max of 1.5 turns, if not set both to 1.25 as a starting point, warm up scooter to normal hot temp. and make sure idle is approx. 1,300 rpms and adjust as needed.
The cold starting is an air bleed passage, controlled by a non adjustable "Wax Choke", the wax choke position is regulated by coolant temperature alone. Passage is open when cold, allowing more air to bypass and higher idle, when coolant warms up, expanding wax pushes passage close. Normal cold starting should not require touching/opening throttle.

zrx212 wrote:

Make sure the brass air-screws on each throttle body are open a max of 1.5 turns, if not set both to 1.25 as a starting point, warm up scooter to normal hot temp. and make sure idle is approx. 1,300 rpms and adjust as needed.
The cold starting is an air bleed passage,  controlled by a non adjustable "Wax Choke", the wax choke position is regulated by coolant temperature alone. Passage is open when cold, allowing more air to bypass and higher idle, when coolant warms up, expanding wax pushes passage close. Normal cold starting should not require touching/opening throttle.

Funny enough I have both air-screws at 1.5 turns out and the idle is at about 1300 rpm.
I don't need to touch/open the throttle on a cold start to get it started, I just need to bring the RPM's up and give is a blip to get it to sit at it's high idle.
I am running out of ideas.

The next step is to replace the K&N air filter (previous owner installed), and "reset" the ECU to make things as stock as possible.

I'm not sure that this is entirely relatable, but my 2004 ST1300 had some annoying cold and hot start issues that were not too dissimilar. Bear in mind that the FI system is pretty similar on that bike with the wax unit etc, just twice as many cylinders and it is a manual not CVT. I eventually traced the fault to a dirty electrical connection in my case the clutch diode; this was visibly OK, but after I properly cleaned the terminals the fault vanished and it has been perfect ever since. Given this, I'd suggest you work your way through the electrical connectors and fuses and disconnect each, give it a blas of contact cleaner, and then reassemble.

I think your plan of replacing the K&N with a stock filter is also pretty sound.

Terry Smith wrote:

I'm not sure that this is entirely relatable, but my 2004 ST1300 had some annoying cold and hot start issues that were not too dissimilar. Bear in mind that the FI system is pretty similar on that bike with the wax unit etc, just twice as many cylinders and it is a manual not CVT. I eventually traced the fault to a dirty electrical connection in my case the clutch diode; this was visibly OK, but after I properly cleaned the terminals the fault vanished and it has been perfect ever since. Given this, I'd suggest you work your way through the electrical connectors and fuses and disconnect each, give it a blas of contact cleaner, and then reassemble.

I think your plan of replacing the K&N with a stock filter is also pretty sound.

Very interesting. Thank you for the information. I like the idea of going though the electrical connections and cleaning with contact cleaner, it is definitely not going to hurt anything.
Corrosion can do strange things.