Rhode Warrior

Supercharged
Joined
Mar 17, 2012
Messages
227
Location
Rhode Island
Ride
2005 Rocket III
My 2005 Rocket was running perfectly all last year. Last month all of a sudden the bike starts to break up at low RPM's under load, like when taking off from a stop or giving it gas from low RPM's. It only does it after I ride the bike for about 20 minutes to a 1/2 hour and it does it consistently.

After it started doing it, I replaced both throttle position sensors. The bike had a bad secondary TPS complete with error message. I replaced that and while I was at it replaced the new style primary TPS. I did the voltage and stepper adjustments on the sensors and it was dead on. I did the adjust ISCV and reset adaption multiple times.

I have TuneECU and I went through all the tests, everything is fine.

Since then I have cleaned the crankcase sensor, (which was very clean anyways), synched the throttle bodies and they're all the same, and removed the secondary plates. I checked all the low voltage connections on the coils and crimped them a little tighter. I took a shot and replaced the stepper motor and it didn't help. I did the headlight relay upgrade as soon as I bought the bike. Could the ignition switch still be the cause?

It starts and runs perfectly, idles at 800 and feels really strong..............except for when I ride it for more than 20 minutes then it has the stumble off idle up to about 2,000 RPM's and a little bit of a rough idle. It's OK above 2,000.

I'm thinking it might be the MAP sensor? Maybe vacuum hoses. I'm racking my brain trying to figure what might change after it warms up. The spark plugs look good too.

My plan is to look at all the readings on TuneECU, especially MAP when it's cold and running right, then look at the readings after it starts to do it and see if I can find the culprit.

The bike has a cat delete, otherwise it's stock. It has fresh gas in it. Bike has only 3,300 miles on it.

Make sense? :confused:
 
I'm a bit reluctant to say this due to the mostly positive comments on here about removing the secondary throttle plates, but a member on another forum removed his and he found exactly the same problem. He posted that there was a loss in throttle sensitivity and the bike would stumble at lower revs.

If you don't find a cure it might be worth putting the plates back just to see.

Right I'm ready for the flack. :D

I'm open to suggestions.
 
I'm open to suggestions.

you should try to figure out if the problem is gas or electric.
you can spray a small amount of starting into the air filter,about as quick as you can no more than 1 second. (i have been doing this for about a year to save my starter and battery and seem to have no side affects so far.) if it tries to fire you have a fuel problem if it don't fire you should check your plugs to see if they are sparking. if the plugs are wet they may be bad.
if you open your gas cap and try to hear when you first turn on ign. do you hear the fuel pump run for about 2 or 3 seconds?
hth herman
 
you should try to figure out if the problem is gas or electric.
you can spray a small amount of starting into the air filter,about as quick as you can no more than 1 second. (i have been doing this for about a year to save my starter and battery and seem to have no side affects so far.) if it tries to fire you have a fuel problem if it don't fire you should check your plugs to see if they are sparking. if the plugs are wet they may be bad.
if you open your gas cap and try to hear when you first turn on ign. do you hear the fuel pump run for about 2 or 3 seconds?
hth herman

It starts OK, it's just rough when I take off or lug it at low RPMs. My plugs look OK and I can hear my fuel pump cycle when I turn the ignition on. :confused:
 
having read your post #1 several times and as you say it is after the engine has heated up/run for 20min I think you may want to check to see if the engine temp sender unit is ok as if it is telling the ECU that your engine is still cold the ECU would be still trying to feed it a richer mix which could cause your stumbling, (these are just my thoughts as the stumbling could be the engine trying to flood) it could also be the map sensor but I would be checking the engine Temp sender unit myself
Hope you solve this quickly as we don't want you pulling all your hair out :eek:
 
It starts OK, it's just rough when I take off or lug it at low RPMs. My plugs look OK and I can hear my fuel pump cycle when I turn the ignition on. :confused:

sorry i went off in wrong direction. i miss read your #4 post
nothing it started before i removed the secondarys
herman
 
having read your post #1 several times and as you say it is after the engine has heated up/run for 20min I think you may want to check to see if the engine temp sender unit is ok as if it is telling the ECU that your engine is still cold the ECU would be still trying to feed it a richer mix which could cause your stumbling, (these are just my thoughts as the stumbling could be the engine trying to flood) it could also be the map sensor but I would be checking the engine Temp sender unit myself
Hope you solve this quickly as we don't want you pulling all your hair out :eek:

That makes sense. I'll start with the engine temp sender.
 
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