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  • Odd Startup Idle With Cam

    Title sounds funny right, odd idle with a cam, of course that's normal! Well I have a few questions...

    When I start my car, I usually have to jab the gas just a bit right when I start it in order for it to not immediately die. This happens much more often in cold weather, while in summer time sometimes I don't have to jab the gas to get her going. It's really all about touch, I can tell when it's going to die so I know when I need to jab the gas. I only hit it a little bit, reaching maybe 1750 RPM's. It's a quick short jab of the gas pedal. When others try to start my car, they usually have quite a hard time because it usually just dies on them, then I tell them to hit the gas a bit and they jab the gas far too hard to say 3k RPM's then the motor sometimes dies when the RPM's fall that fast.

    So a bit hard to start, normal for a cam, right? Well there is another weird aspect to it. When I start it up, sometimes the idle bounces around violently from 1600 to near stall. This occurs far more in the winter and especially when I have to jab the gas. The idle will bounce around a bit when I don't have to hit the gas but not nearly as violently as when I do hit the gas. While the motor is revving it's heart out, I watch my wideband get richer and richer until the RPM's steady out. I am guessing this is my PCM making it pig rich for warm up when it's cold out, which also smooths my idle.

    After this, my wideband starts to creep up back towards 14.7 and my RPM's slowly fall to my normal set idle speed.

    Is this normal, or do I need to change something with my tune? I mean I understand it getting richer when I start up especially when cold, but the violent revving seems odd. Why does the car not get richer faster? It does this for maybe 20 seconds until it is rich enough to totally stop. I can get a video if desired.
    SpudFiles
    Blast vegetables and whatever else you can think of!
    Theopia
    Enjoy life online.

    1996 3500GP Coupe, "Bright White".
    3500 swap, 60degreeV6 1393 Cam, Ported Intakes, Comp Cams Valve Springs, 65mm TB, Custom Pushrods, S&S Headers, 97 PCM with DHP Powrtuner, 2.5" back to dual Hooker Aerochambers, SS Brake Lines, Addco swaybar, KYB's, Intrax Springs, STB's, etc!

  • #2
    My cam behaves almost identical to this in cold weather.
    Lots of mods cost lots of $$
    http://www.cardomain.com/ride/2598719/1

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    • #3
      I would guess its in the tuning with startup idle speed, IAC airflow values, or maybe spark advance. Cold weather normally calls for richer conditions but I am basing this on obd1 tuning.
      Ben
      60DegreeV6.com
      WOT-Tech.com

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      • #4
        My idle bounces from 800 to 2K for about 5 minutes on a cold start.. and that's after it's in closed loop.

        I'd work on your idle fuel tables and check any tables relating to intake air temp VS injector PW, or coolant temp VS PW. You should be able to sort that out.
        Past Builds;
        1991 Z24, 3500/5 Spd. 275WHP/259WTQ 13.07@108 MPH
        1989 Camaro RS, ITB-3500/700R4. 263WHP/263WTQ 13.52@99.2 MPH
        Current Project;
        1972 Nova 12.73@105.7 MPH

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        • #5
          Yeah the tune is not dead on for cold weather. Also make sure the IAC is clean. Mine has surged recently too I noticed. Last time it did that was winter as well and then it got worse and I had to get a different IAC after cleaning failed. I can usually stop the surging by putting it in Drive with the foot on the brake, then go back to neutral/park and it calms down then. It will start sometimes if I rev it in park/ neutral sitting still.

          You have tuned the warm weather part, now you need to tune the cold weather part and you'll be done.
          sigpic New 2010 project (click image)
          1994 3100 BERETTA. 200,000+ miles
          16.0 1/4 mile when stock. Now ???
          Original L82 Longblock
          with LA1, LX9, LX5 parts
          Manifold-back 2.5" SS Mandrel Exhaust. Hardware is SS too.

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          • #6
            I had this problem bad with my milzy cam which resembled your specs closely... With my new cam I don't have as much of an issue but it still bounces a little in cold weather, not as much as before tho.

            Got Lope?
            3500 Build, Comp XFI Cam 218/230 .050 dur .570/.568 lift 113LSA
            Fully Balanced, Ported, 3 Angle Valve Job, 65mm TCE TB, S&S Headers.
            Stage-1 Raybestos/Alto 4t60e-HD, EP LSD, 3.69FDR
            12.61@105 Epping NH Oct 2015 Nitrous 100shot (melted plugs) 13.58@98.8 N/A 3200LBS

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            • #7
              Even mine will do this, although its only a matter of a few hundred RPM. Mine will do this cold or warm, doesnt matter. Although I know I have problems that need to be addressed.
              sigpic
              1994 Oldsmobile Cultass Supreme SL
              3400/Getrag 284 5spd
              1995 Chevy K1500 350c.i. 5spd Z71
              350/NV3500 5spd
              2014 Chevrolet Malibu LS

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