cold start up engine surging

Discussion in 'Touring Models' started by roadhog54, Aug 2, 2011.

  1. roadhog54

    roadhog54 New Member

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    I bought A use 2009 ultra classic with about 9800 mile on it. I have about 14500 mile on it now, but the bike has alway surge from 900 to 1400 rpm.you ride it for about 5 block and it seems to idleand run fine. i got rush 1 3/4 slipon mufflers on and all so installed dobeck TFI tuner, have not intalled sc air cleaner yet. what do i need to check for
     
  2. glider

    glider Veteran Member

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  3. Hoople

    Hoople Account Removed

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    Are you saying that if the engine is stone cold, the first 5 blocks you ride it, the bike surges? And after it is warmed up, it runs fine?
     
  4. roadhog54

    roadhog54 New Member

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    you dont feel it when your rideing it or above say 1500rpm

    hoople yea thats about it
     
    Last edited by a moderator: Aug 2, 2011
  5. TQuentin1

    TQuentin1 Well-Known Member Staff Member Moderator

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    After checking for the air leak like Glider suggested above, it is very important to make sure you are shutting the bike off after it has achieved a stable idle. Try hands off the bars for 15 second before you shut down, and then only your thumb or fore-finger on the kill switch. Then turn off the main key switch.

    I have seen lots of folks roll up on site and kill the engine while they are still rolling. Engine has not idled down, so when the ECU sees start up again it is hunting for idle.

    Give the process above a try and see what happens.

    TQ
     
  6. glider

    glider Veteran Member

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    Excellent recommendation TQ!
     
  7. Hoople

    Hoople Account Removed

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    During the engine warming up period (which is very short) there is a "warm up fuel table" (or enrichment factor as it's called) that is used by the engine to enrich the fuel mixture. That is needed because a cold engine can not fully vaporize the injected fuel. This enrichment factor is just like choking a carb. There is also an "idle up" table that is used by the ecm. It is perfectly normal to see an uplift in RPM (just like an engine w/ a carb) during the short warm up period.
    Just because the bike has EFI, it does not mean the engine no longer needs to be choked during cold starting or no longer needs a little help during warm up.

    You did mention that the bike always has done this. So has mine. There is a stop light about 5 blocks from my house. 90% of the time, my warm up table finishes by the time I get to that light,,and I can tell because the idle up RPM is now down to normal (1000).

    The warm up enrichment factor has a "slope" which can be altered using a SEST. I adjusted the slope characteristics to eliminate most of the surging but I left my idle up table factory stock. When I seen my idle settle in at 1000, that tells me that the enrichment table is no longer being used and the ECM has toggled over to a straight fuel map..

    ***Now once the engine is warmed up,,,,if you still have surging or a racing idle, that's a whole different story. Lets say for example you filled up with fuel and it takes you 5 minutes before you restart the bike. I would NOT expect the idle to be lifted or the bike to surge when taking off down the road. If it does, then that is a whole different story. But from a STONE COLD engine, I would consider a 5 block warm up to be perfectly normal.***

    But like I said earlier, if you really want to, you can make changes those two settings but it will take a SEST and a little trial and error on your part to do it.

    (With 15K on the bike, make sure the stock air filter is clean)
     
  8. glider

    glider Veteran Member

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    Just a thought here, you may want to have your dealer check what download is in the bike. It wouldn't be the first time that the wrong download was installed in a bike and the results would be pretty much what you are having. The fuel map may be too lean for your bike.
     
  9. roadhog54

    roadhog54 New Member

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    i check for a air leak did not see a change in rpm ,bike run great when warm it just that first start up after bike been cooled down for a whilethats driven me nuts. I think I all ways kill bike after a stable idle but i will double check myself. my have to let dealer check download
     
  10. ironmark

    ironmark Junior Member

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    My bike does the same thing as yours. When I start the bike when it is stone cold the idle will range from 1200 to 1500 rpm's when the bike warms up the idle smooths out. I attribute it to IAC (Idle Air Control Actuator) not getting the correct message from the ECM. I didn't have the problem until I had the custom dyno done to my bike and I never done anything about it because I am hesitant about letting a tech hook the computer to my bike and taking a chance on loosing the custom fuel map. A friend of mine is a HD tech and he said that he could access the ECM and smooth the idle out.