Low idle on cold start

Hi new 2005 SW owner and loving it, I’m finding this forum very helpful, friendly and full of information.
The bike has 13k miles and I’ve only put a couple hundred on so far so I don’t have a lot of time on it.

I am noticing that on the first start warm up of the day, the bike starts fine, but then after a few seconds goes into a low/rough idle (under 1000 rpm), I am able to keep the RMP’s up with the throttle and after about 30 seconds she will idle fine and doesn’t seem to have any issues after that, this doesn’t seem right. I assume in a normal start up scenario, the bike would start and have a high idle 2k +/- while on choke and then slow down to 12-1300rpm once it’s warm.
If that’s true I seem to have an issue.
I’ve done a good amount of searching on this forum and found similar issues idle issues (not specifically cold start), with different fixes…fuel pressure regulator, vacuum leak, bad fuel, low battery, run a few tanks of Sea Foam or Techron.

Any ideas where to start?
I’m planning on running some fuel injector cleaner just due to the age of the motor and piece of mind.

Thanks for any advice provided.

The choke is an enrichment circuit opened/closed by a "Fast Idle Wax Unit" that's coolant heated to close passage, besides checking for bad vacuum hoses, etc.  Check/count turns on air screws, sometimes air screws are turned by accident, affecting synchronization, and/or too far out, a good general setting for both airscrews is 1.25 out to a max 1.5, if set over 1.5, it could affect the fuel press at idle and/or fast idle operation when cold or even TPS idle position setting slightly. Because the idle screw was used to compensate for other issues it changes the throttle plate position and/or vacuum signal to regulator.
If you have the means to synch. air screws do it, but is not very critical IMO.

Thmp Thmp before you start fiddling to it might be worth putting a thankful something like Shell Ultra in and going for a 100 mile ride.
If the bike is only doing intermittent, short runs that could be the problem.

BOOSTERPLUG FUEL INJECTION TUNING - YOUR MOTORCYCLE WILL LOVE YOU FOR IT. The BoosterPlug is accepted worldwide as the best possible fuel injection tuning method- and will transform your motorcycle from OK to Absolutely marvellous. No need to spend a fortune on a complicated Power Commander kit + endless Dyno hours to make your bike run as it should have done from the factory. The BoosterPlug tuning module is installed in less than 10 minutes. It plugs directly into your motorcycles wiring harness using original connectors, No cutting or splicing wires, no complicated programming, no problems. A tried and tested kit to solve the common stalling and idle problems. The BoosterPlug fuel injection tuning kit is designed to eliminate the usual fuel injection problems that haunts all modern motorcycles. The too lean air/fuel mixture on the standard bike will make idle and low speed running weak, and the throttle action will be horribly on/off like. The small controlled fuel enrichment with the BoosterPlug will solve the common fuel injection problems and make your motorcycle easier and safer to ride.

09 Swing with 21k on the clock.

The Swing uses a 3 stage accelerator, the first stage (idle and tickover) is set lean to meet emmision targets, stage 2 and 3 run complete maps and require no alterations.
I fitted the above item to my std swing which then raised the tickover to 1800rpm, which I then lowered to 1300rpm.
The test ride was so much smoother, and more responsive at low speed, and tickover very stable.
I would rate this product a must for the serious rider.
Haven't done a fuel use comparison as I am very very happy with the set up now, slight increase around town but what the heck...

zrx212 wrote:

The choke is an enrichment circuit opened/closed by a "Fast Idle Wax Unit" that's coolant heated to close passage, besides checking for bad vacuum hoses, etc.  Check/count turns on air screws, sometimes air screws are turned by accident, affecting synchronization, and/or too far out, a good general setting for both airscrews is 1.25 out to a max 1.5, if set over 1.5, it could affect the fuel press at idle and/or fast idle operation when cold or even TPS idle position setting slightly. Because the idle screw was used to compensate for other issues it changes the throttle plate position and/or vacuum signal to regulator.
If you have the means to synch. air screws do it, but is not very critical IMO.

This is what I am talking about, that is a lot of good information. Does the "Fast Idle Wax Unit" ever go bad? I haven't had time to check any of this out yet, but what is the best way to access the air screws and vacuum lines? Under the seat near the intake or the little hatch below the seat?
Thank you for this information and pictures.

steve_h80 wrote:

Thmp Thmp before you start fiddling to it might be worth putting a thankful something like Shell Ultra in and going for a 100 mile ride.
If the bike is only doing intermittent, short runs that could be the problem.

I am not opposed to the option and think it is a good one, I just need to find a dry enough day of get her out on the road.

JohnyC wrote:

BOOSTERPLUG FUEL INJECTION TUNING - YOUR MOTORCYCLE WILL LOVE YOU FOR IT. The BoosterPlug is accepted worldwide as the best possible fuel injection tuning method- and will transform your motorcycle from OK to Absolutely marvellous. No need to spend a fortune on a complicated Power Commander kit + endless Dyno hours to make your bike run as it should have done from the factory. The BoosterPlug tuning module is installed in less than 10 minutes. It plugs directly into your motorcycles wiring harness using original connectors, No cutting or splicing wires, no complicated programming, no problems. A tried and tested kit to solve the common stalling and idle problems. The BoosterPlug fuel injection tuning kit is designed to eliminate the usual fuel injection problems that haunts all modern motorcycles. The too lean air/fuel mixture on the standard bike will make idle and low speed running weak, and the throttle action will be horribly on/off like. The small controlled fuel enrichment with the BoosterPlug will solve the common fuel injection problems and make your motorcycle easier and safer to ride.

09 Swing with 21k on the clock.

The Swing uses a 3 stage accelerator, the first stage (idle and tickover) is set lean to meet emmision targets, stage 2 and 3 run complete maps and require no alterations.
I fitted the above item to my std swing which then raised the tickover to 1800rpm, which I then lowered to 1300rpm.
The test ride was so much smoother, and more responsive at low speed, and tickover very stable.
I would rate this product a must for the serious rider.
Haven't done a fuel use comparison as I am very very happy with the set up now, slight increase around town but what the heck...

Funny you should mention the Booster Plug. When I was giving the bike a once over, I saw a little temp sensor by the intake, I followed the wire to under the seat and found a Booster Plug...but it was disconnected. I plugged it in the see if it would change things, but no luck, at least in the driveway, I am hoping that a nice ride will sort things out. I suspect it was disconnected by the previous owner trying to figure out this same issue.

Stoked that the bike came with the Booster Plug.

I would stick a couple of shots of Dipetane fuel lubricant(zero additives)(not sure if available in the states) into the tank and give the Swing a good runt(like you stole it) along the freeway, never fails to sort injection/emissions problems for our vehicle yearly tests.

Happy riding.

JohnyC wrote:

I would stick a couple of shots of Diptane fuel lubricant(zero additives)(not sure if available in the states) into the tank and give the Swing a good runt(like you stole it) along the freeway, never fails to sort injection/emissions problems for our vehicle yearly tests.

Happy riding.

Unfortunately we do not have Dipetane, but we do have similar cleaners that I am planning on adding before I go for my "clean out" ride.

I really appreciate all of the ideas you all are offering.

I have owned three silverwings and never had to adjust any of the fuel settings. Once a year in the spring I had some fuel injector cleaner and run good fuel in her, take out on the highway for a 30 min high speed run. Smooth as silk. good luck ps check your air filter.

Murf wrote:

I have owned three silverwings and never had to adjust any of the fuel settings.  Once a year in the spring I had some fuel injector cleaner and run good fuel in her, take out on the highway for a 30 min high speed run.  Smooth as silk.  good luck ps check your air filter.

It's a Honda, so I suspect that not much needs to be done.
I did check the air filter, the previous owner put in a K&N and he did over oil it a bit as some oil was dripping out of the air box drain. I was wondering if some oil might have made it into the intake or soiled the MAF sensor, but I see no signs of oil residue.

Just a suggestion but the injection system mechanically opens the starter valves when the coolant is cold, and progressively closes these back to the warm idle position as the coolant heats up. Sounds like your bike is doing this, but the fuel mix is a bit off until it is warm. That suggests to me that the issue may be the engine coolant temperature sensor either failing or with a connection/wire issue, so the injection volume is incorrect (probably too lean) for the cold temperature. The ECT sensor has two parts, one drives the gauge on the dash, and the other sends a resistance signal to the ECU. At the very least I'd suggest unplugging and reconnecting the plug to the ECT sensor.

My bike does not fast idle when the weather is warm here in Florida but it does fast idle when the weather is chilly. One summer day I piled a few ice cubes around the wax unit and it fast idled at about 1700 rpms. I had the chance to buy a throttle body with wax unit attached(cheap) and it acted like my original did. I adjusted the air screws with gauges and the bike performed slightly better. It doesn't fall below 1,000 rpms and now I know that it is just the warm weather so no worries.

Thmp Thmp wrote:

Murf wrote:

I have owned three silverwings and never had to adjust any of the fuel settings.  Once a year in the spring I had some fuel injector cleaner and run good fuel in her, take out on the highway for a 30 min high speed run.  Smooth as silk.  good luck ps check your air filter.

It's a Honda, so I suspect that not much needs to be done.
I did check the air filter, the previous owner put in a K&N and he did over oil it a bit as some oil was dripping out of the air box drain. I was wondering if some oil might have made it into the intake or soiled the MAF sensor, but I see no signs of oil residue.

SW doesn't have a MAF sensor. PGMFI on Honda's never did.
Either someone turned some adjustments on throttle body, or a vacuum leak is most likely the problem.

Booster Plug only changes the air intake sensor reading to the ECU and adds a bit more fuel mixture.

Terry Smith wrote:

Just a suggestion but the injection system mechanically opens the starter valves when the coolant is cold, and progressively closes these back to the warm idle position as the coolant heats up. Sounds like your bike is doing this, but the fuel mix is a bit off until it is warm. That suggests to me that the issue may be the engine coolant temperature sensor either failing or with a connection/wire issue, so the injection volume is incorrect (probably too lean) for the cold temperature. The ECT sensor has two parts, one drives the gauge on the dash, and the other sends a resistance signal to the ECU. At the very least I'd suggest unplugging and reconnecting the plug to the ECT sensor.

Thanks for this information. Very helpful. I will check these connections and maybe add some dielectric grease while I am in there checking for vacuum leaks.
I haven't had the bike for long, but a few times when I started it everything seemed normal. It has been cold and rainy lately and this issue started, so I could see it being a temperature related issue. Do you know if the sensors go bad very often, or is it usually the a wiring issue?

Mech 1 twa wrote:

Thmp Thmp wrote:

Murf wrote:

I have owned three silverwings and never had to adjust any of the fuel settings.  Once a year in the spring I had some fuel injector cleaner and run good fuel in her, take out on the highway for a 30 min high speed run.  Smooth as silk.  good luck ps check your air filter.

It's a Honda, so I suspect that not much needs to be done.
I did check the air filter, the previous owner put in a K&N and he did over oil it a bit as some oil was dripping out of the air box drain. I was wondering if some oil might have made it into the intake or soiled the MAF sensor, but I see no signs of oil residue.

SW doesn't have a MAF sensor. PGMFI on Honda's never did.
Either someone turned some adjustments on throttle body, or a vacuum leak is most likely the problem.

Booster Plug only changes the air intake sensor reading to the ECU and adds a bit more fuel mixture.

Thank you for the MAF clarification. I was just assuming it had one.
I will start with checking for vacuum leaks and go from there.

Does the engine stall if you don't keep up the low revs with the throttle?

I ask because my SW idling speeds can vary with amount of use, weather, ambient temperature, engine temperature etc. Sometimes, if laid up for a few weeks in the winter, she fires up and then almost stalls but hangs on in there for a second and then kinda settles down. I don't touch the throttle.

I rarely see my tacho showing a regular and constant idle speed. It's lived with it for 6 years and it's never been an issue.

Once warmed up and then waiting in traffic etc., it's usually around the 1100/1200rpm mark which I consider to be about right.

Loosemarbles wrote:

Does the engine stall if you don't keep up the low revs with the throttle?

I ask because my SW idling speeds can vary with amount of use, weather, ambient temperature, engine temperature  etc. Sometimes, if laid up for a few weeks in the winter, she fires up and then almost stalls but hangs on in there for a second and then kinda settles down. I don't touch the throttle.

I rarely see my tacho showing a regular and constant idle speed. It's lived with it for 6 years and it's never been an issue.

Once warmed up and then waiting in traffic etc., it's usually around the 1100/1200rpm mark which I consider to be about right.

The RPM's get really low, but not sure if it will stall as I have always kept it running by applying some throttle.