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Thread: Cat warm up mode going bonkers

  1. #1
    Tuner in Training
    Join Date
    Jul 2011
    Posts
    28

    Cat warm up mode going bonkers

    What is the deal with GM's DI vehicles cat warm up mode?? A few months ago still in the middle of winter my cat warm up mode started acting weird, it would miss, shake, and throw misfire CEL. It would come and go so I kind of lived with it. Now it does it every time I start the car while the engine is cold and it start up in cat warm up mode. As the weather got warmer I haven't had any CEL's lately, but today I got the darn CEL again for multiple misfire on cy 1, 2 and 5, including multiple. The crazy thing about this whole thing is that it only idle rough and misfire while in cat warm up mode. Come out of cat warm up mode and everything is fine, no more CEL and no more rough idle. I checked everything I could except for my injectors and everything is fine. I'm just not convinced enough on new injectors as of right now. I know some of you guys are very familiar with this issue. Please shed some light on this as I am going nuts.

  2. #2
    Potential Tuner
    Join Date
    May 2007
    Posts
    2
    Thread from the dead!

    I've had this issue for the last couple of years with my LNF Cobalt on just cyl 1, it randomly decides when it wants to do it though. New plugs, swap plugs, swap ignition coils, new air filter, change oil and filter, took to GM for their fuel system cleaner. Nothing has fixed it so far.

    Anybody else figure out this problem?

  3. #3
    Tuner in Training
    Join Date
    Mar 2012
    Posts
    22
    Is this on a LNF?