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  • #1

    LT1 really rough startup...

    Hello, I got a 95 z28, 70k miles, hypertech about it. Occasionaly when you start it up it will idle rough, it will buck violently and it sounds like its running on three cylinders. The rough idle is around 200 to 300 RPM and giving it gas does not help at all. Now at this time you turn the ignition off and start it again and it starts and runs like new. Again this happen rarely every now and then. Also there are noe SES indicators. It it is on its second opti which was installed in 1997and the EGR was replace a couple of years ago. Aside from the startup issue the engine runs hard and strong all the time. Any suggestions.
    Thanks
    1995 Z28 Convertible, 350ci LT1 73K miles M6.
    Dyno results: 301.5 RWHP 326.7 RWTQ
    Performance Mods 4.10 gears, AS&M CAI, MADZ28 tune, Borla catback, RK Sport mid-length headers, LT4 valve springs, CC pro mag 1.6 RR's, LT4 KM, MSD OVC wires, TB bypass, 160 t-stat, SLP clutch plate w/Kevlar dual friction disk, 52MM TB, TB air foil, 1LE aluminum driveshaft, ASP UD pulley, LS1 brakes w/ Hawk HPS pads, LCA's and PHB.
    Tags: None
  • #2
    Originally posted by wrd1972
    Hello, I got a 95 z28, 70k miles, hypertech about it. Occasionaly when you start it up it will idle rough, it will buck violently and it sounds like its running on three cylinders. The rough idle is around 200 to 300 RPM and giving it gas does not help at all. Now at this time you turn the ignition off and start it again and it starts and runs like new. Again this happen rarely every now and then. Also there are noe SES indicators. It it is on its second opti which was installed in 1997and the EGR was replace a couple of years ago. Aside from the startup issue the engine runs hard and strong all the time. Any suggestions.
    Thanks
    Mine does that about once or twice a year. I just turn it off and restart it. I figure GM must have used Microsoft and it needs rebooting.
    2002 Electron Blue Vette, 1SC, FE3/Z51, G92 3.15 gears, 308.9 RWHP 321.7 RWTQ (before any mods), SLP headers, Z06 exhaust, MSD Ignition Wires, AC Delco Iridium Spark Plugs, 160 t-stat, lots of ECM tuning

    1995 Z28, many mods, SOLD

    A proud member of the "F-Body Dirty Dozen"

    Comment

    • #3
      Maybe if I install service pack 2.
      1995 Z28 Convertible, 350ci LT1 73K miles M6.
      Dyno results: 301.5 RWHP 326.7 RWTQ
      Performance Mods 4.10 gears, AS&M CAI, MADZ28 tune, Borla catback, RK Sport mid-length headers, LT4 valve springs, CC pro mag 1.6 RR's, LT4 KM, MSD OVC wires, TB bypass, 160 t-stat, SLP clutch plate w/Kevlar dual friction disk, 52MM TB, TB air foil, 1LE aluminum driveshaft, ASP UD pulley, LS1 brakes w/ Hawk HPS pads, LCA's and PHB.

      Comment

      • #4
        Originally posted by wrd1972
        Maybe if I install service pack 2.
        Good answer!

        You know if you think about it, when you buy something like an MP3 player or a piece of software, you always have firmware upgrade and software updates. It's a wonder car manufacturers don't have firmware updates. I know there are some things I want to fix about the software in my car. Like the over rich condition at WOT.
        2002 Electron Blue Vette, 1SC, FE3/Z51, G92 3.15 gears, 308.9 RWHP 321.7 RWTQ (before any mods), SLP headers, Z06 exhaust, MSD Ignition Wires, AC Delco Iridium Spark Plugs, 160 t-stat, lots of ECM tuning

        1995 Z28, many mods, SOLD

        A proud member of the "F-Body Dirty Dozen"

        Comment

        • #5
          That is a really good point! Why in the heck can't auto manufacturers have a system to update the firmware on our PCMs??
          Tracy
          2002 C5 M6 Convertible
          1994 Z28 M6 Convertible
          Current Mods:
          SLP Ultra-Z functional ramair, SS Spoiler, STB, SFCs, Headers, Clutch, Bilstein Shocks, and TB Airfoil. 17x9 SS rims with Goodyear tires, 160F T-Stat, MSD Blaster Coil, Taylor wires, Hurst billet shifter, Borla catback with QTP e-cutout, Tuned PCM, 1LE Swaybars, 1LE driveshaft, ES bushings, White gauges, C5 front brakes, !CAGS, Bose/Soundstream audio, CST leather interior, synthetic fluids

          Comment

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