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328 Rough Warm-Up Period

Discussion in 'Technical Q&A' started by Freestyle, Jan 12, 2008.

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  1. Freestyle

    Freestyle Rookie

    Dec 24, 2007
    21
    #1 Freestyle, Jan 12, 2008
    Having a little difficulty when engine is cold. It starts a little hard and and runs rough until it's fully warmed-up. Just replaced a bad throttle switch.
     
  2. f355spider

    f355spider F1 World Champ
    Owner Rossa Subscribed

    May 29, 2001
    18,047
    USA
    #2 f355spider, Jan 12, 2008
    From a cold start, what is the idle speed?
     
  3. fletch62

    fletch62 Formula Junior

    Mar 8, 2004
    333
    Fairhope, AL
    Full Name:
    Larry Fletcher
    #3 fletch62, Jan 12, 2008
    Not enough info, but one thing it could be is warm up regulator. Remove the air filter and start the engine cold. Then put your finger on the airflow sensor plate and push it down .002" to .004" and if it gets better, if so you need to put a "CIS" type gauge on it and check your pressures. If you need more info on CIS injection call me.

    Larry Fletcher
    251-929-3771
     
  4. Freestyle

    Freestyle Rookie

    Dec 24, 2007
    21
    #4 Freestyle, Jan 13, 2008
    I'm now getting around 1500 rpm's when I first start the engine and it's cold. I don't know if it helped but I adjusted the small fuel line that goes to the new cold start valve at the intake manifold. As the engine warms-up it gradually settles down to between 900-1000 rpms, but idles rough ever since I installed the new throttle switch. I'll perform the test for the warm-up regulator and will also try adjusting the throttle switch slightly. If I still have a problem I'll give you a call. Thanks for the help!

    JP
     
  5. Adaptel

    Adaptel Karting

    Jul 21, 2007
    89
    Concord, NH USA
    Full Name:
    Kevin Pearson
    #5 Adaptel, Jan 25, 2008
    You say that it has been "since you installed new throttle switch". Make sure the switch is adjusted correctly, as it can be rotated about 2 degrees when the fasteners are loosened. Some switches are designed only to provide feeback in the "Wide Open Throttle" state (2-wires on connector), and others also detect the "closed throttle, or idle state (3-wires on connector). I think your motor uses the latter, and make sure the lower-limit switch is being pressed when the throttle plate is closed.

    This is easy to test. With the motor off, slowly rotate the throttle open and listen for the "click" of the microswitch deactivating. This switch is important to be pressed in at idle so the engine is in the correct "state" for idle. If you can't hear it, adjust the switch by rotating it counter-clockwise. Be careful that you don't rotate it too much so that the switch is holding the throttle plate open a tiny bit. You want the throttle-stop to be the screw on the other side, and not the switch because besides a high idle, you will be replacing this switch again soon.
     

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