Cold Stumble

[GaTeach]

Has anyone cured the cold stumble?

[shooter]

Teach , I've never had it. I've heard others talk about it. I do have the Guhl flash but rode it three years before that. I mostly run Shell 93. Not trying to start that debate. If you haven't run any Lucas or Seafoam in the bike you might try that. I believe it's caused by a lean condition. A good cleaner might help. With your mileage have you had a set of plugs installed?

[GaTeach]

I haven't had new plugs. My mechanic thinks it's the fuel pump and they are replacing the fuel pump under warranty. (I don't think it's the fuel pump, but WTH, let them replace the fuel pump)

I've tried Seafoam.

Right now, I have to let her warm up to operating temp or else I get the stumble.

[shooter]

I haven't had new plugs. My mechanic thinks it's the fuel pump and they are replacing the fuel pump under warranty. (I don't think it's the fuel pump, but WTH, let them replace the fuel pump)

I've tried Seafoam.

Right now, I have to let her warm up to operating temp or else I get the stumble.

Maybe not so much the pump as the in tank screen/ filter. I still think it's a lean condition , lack of fuel.

[53driver]

Maybe not so much the pump as the in tank screen/ filter. I still think it's a lean condition , lack of fuel.

If it's a screen or filter issue, why would it seemingly disappear at operating temperature?
I been chasing this one for 50,000 miles now....I'm ready to believe almost anything!

[shooter]

If it's a screen or filter issue, why would it seemingly disappear at operating temperature?
I been chasing this one for 50,000 miles now....I'm ready to believe almost anything!

Once the engine is warmed up it requires less fuel to operate efficiently.

[53driver]

I think new plugs helped Isleen's stumble, but it's still there.
I'm getting an ECM to Guhl soon - too much performance going to waste in the name of the EPA.

While I'm waiting/getting the reflash, I'm going to run a full can of seafoam in the next 3 tankfuls just to ensure her pipes are clean.

It's embarrassing riding out of the driveway and have the bike buck and hiccup.....

[53driver]

I am in FULL agreement that there is a fuel flow issue.
But is it one or all of the following:
Electrical
- The demand signal
- The demand signal feedback loop
- A sensor somewhere giving false information
Mechanical
- The fuel pump not responding to the demand flow (main jet / pilot jet issue??? lol )
- A filter
- Mechanical feedback in the throttle body

I believe it's in the ECU - no one with a Guhl reflash has had this problem.
Can't wait to get mine to him and back.

I also want to see if GaTeach's mech had the solution.

[shooter]

Steve I do know a couple guys on another forum that still had a problem. Sent the ECU back to Guhl a second time and no issues after that. If it was me I would tell Don about the problem so he could pay special attention to that area.

[Pumper]

Steve,
I believe also it is in the ECU...Fuel injection has a cold start circuit. That is controlled through the ECM of whatever vehicle it is.
Cold start stumbles, typically are a result of misinformation being sent (sensor) to the ECM. Hence the ECM will produce a lean condition.

Sensors are hard to diag. as they have gremlins and we all know how hard they are to catch...

Has anyone had a code thrown due to the stumble??