Car runs Rough when cold

Posted by Dready, Nov 25, 2008
Newbie Forum - Beginner DSM modification questions and discussions. Common, repetitive, and general discussions will get dumped here from other tech forums. Unless you're a Probationary member you shouldn't post threads here.

  1. Dready

    Dready Proven Member

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    NMB, South_Carolina
    My car runs rough and kinda bucks a little when the coolant temp is still low.

    I let the car warm up for atleast a minute but it still runs rough WHILE DRIVING until it gets to Normal operating temperature.

    Could the coolant system be too full of coolant?

    Would sparkplugs help this issue?

    Any Ideas?

    Like i said the car runs perfect after it gets warmed up..its just really annoying for the 1st few minutes.
    #1
  2. habitatguy187

    habitatguy187 Proven Member

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    Do you have a aftermarket boost gauge? If so what's your vacuum read?
    #2
  3. 95redturboawd

    95redturboawd Proven Member

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    I have the same issue... I'm assuming it's fairly commen but I just bought some new plugs... I need to get a gapping tool first but I'll post back with my results.
    #3
  4. RayBan GST

    RayBan GST Proven Member

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    its not common ( it should be smooth even when its cold) try changing your OIL also it may help

    check the spark plugs and the wires

    good luck :thumb:
    #4
  5. cano86

    cano86 Proven Member

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    In my car I'll leave it as common since I already changed oil,coolant,spark plugs/and wires,and the vacuum is the same as when is at temperature so I give up at least is only like that for a minute or two but no more.
    #5
  6. romeen

    romeen DSM Wiseman

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    Check the ECT (Engine Coolant Temperature) sensor.
    #6
  7. habitatguy187

    habitatguy187 Proven Member

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    Indianapolis, Indiana
    The reason I ask about the vacuum is because if you have a vacuum leak, then you'll be running rich, and while the car is starting cold it's gonna idle high. Add that high idle to the richness caused by a vacuum leak and your car's gonna feel very bogged down and run like crap. So again, what's your vacuum reading?
    #7
  8. EclipticalGS

    EclipticalGS Proven Member

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    walker, Michigan
    Thats kinda weird. Whe i cold start my car in 20 degree weather it will have a 1100 rpm idle, vacuum gauge runs a 20 out of 30.....then when it warms up, idle drops to 850rpm and vacuum gauge goes to 15/30. my A/F gague shows lean. I have a vacuum leak and i fixed it.

    When you start your car cold...rev in neutral..does it sputter and spit? I thot at first it was spark plugs. went out and put like 150 on MSD ignition, MSD wires, and NGK Iridium plugs and it didnt help the problem.

    GLuck
    #8
  9. cano86

    cano86 Proven Member

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    hartford, Connecticut
    My car vacuum is also 20/30
    #9
  10. SexaiPander

    SexaiPander Probationary Member

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    How do you check your vacuum reading??
    #10
  11. habitatguy187

    habitatguy187 Proven Member

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    Indianapolis, Indiana
    An aftermarket boost gauge that shows negative (vacuum, -hg) and positive (boost) pressure. This should be the first thing that you buy.
    #11
  12. habitatguy187

    habitatguy187 Proven Member

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    Indianapolis, Indiana
    Your vacuum reading should be higher when the car is warming up. (higher when idle rpms are higher) If it's the same when idling high as when idling normal, there's something wrong.
    #12
  13. ApexVIII

    ApexVIII Proven Member

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    mine is kinda funny like that to i think its normal

    when i first start it and drive it, like start it put it in gear and go it is kinda weird

    but if i let it idle for like 35sec. then it is all good

    which when it is cold out side you should let you car warm up just a little, and get pretty close to fully warm befor boosting. thats what i do no boost untill its warm.
    #13
  14. hollywood_ikr

    hollywood_ikr Proven Member

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    +1 Mee 2. I do it a lot more though. I turn it on put it on the turbo timer and then I go back inside my house and finish getting ready. When I come back I know the car is ready for whatever I throw at it :cool:

    :dsm:
    #14
  15. 92ts1

    92ts1 Proven Member

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    From what I know it's fairly common, more so when you do the vacuum mod. When you delete the sensors on the drivers side of the engine bay it really does it.. All of my cars have done it. One of the sensors on the firewall on the drivers side is a cold start vacuum solenoid that actuates vacuum when the ECT is low so it won't run as rich and buck.
    #15
  16. badboy4lyf069

    badboy4lyf069 Probationary Member

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    It seems like its pretty common
    I have the same exact problem. The vac gauge reads 20/30, and it only runs smooth once it warms up...my bo0st leak that i cant seem to get rid of doesnt help very much either :|
    #16
  17. tkelly27

    tkelly27 Proven Member

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    There is the FIAV
    http://www.dsmtuners.com/forums/newbie-forum/315778-fiav.html

    The ISC, and a few other parts that affect how it runs. Mine didn't start the same after I got rid of the fuel pump solenoid. I've more or less tuned it out though. Still rough, but much less so. I don't know a whole lot about all that, but there's much more that can go wrong besides the CTS and a vacuum leak : )

    When you let your engine idle to warm up, it will be ready for anything. Your transmission however, will still be cool at best, and your rear differential (if you have one) will still be at ambient. From everything I've heard, the best way to warm up a street car is to drive it normally. This brings the engine up to operating temperature more quickly and makes sure all the other things that need to heat up are good to go.
    #17
  18. gregalmighty

    gregalmighty Proven Member

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    Yes, its common. The ECU adds more fuel when the car is cold. It isn't as noticeable with a stock FP but if you have a higher flow FP esp. with a stock FPR then you really notice it. The ECU stays in closed loop operation until the coolant temp reaches normal temperature. Once this happens the ECU goes into open loop mode and stops dumping the extra fuel.

    This article may help: The Essential Primer on the Diamond-Star Engine Control Units - Chapter 5
    #18
  19. SexaiPander

    SexaiPander Probationary Member

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    Ok well i already have that so thanks :)
    #19
  20. 95redturboawd

    95redturboawd Proven Member

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    Sorry to bump an old thread, but I said I would post back after installing new plugs and I just got around to doing it. Turns out the old plugs weren't OEM, they were NGK but a different model. I put in the OEM ones and it runs much better when I first start off. Used to sort of bog if I got on it at all, now it hardly does. So try swapping out the plugs.
    #20

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