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  • #1

    Wierd HP curve . . . ideas?

    I'm Newb here and I have an issue with my 2000 SS . . . I was hoping all the great people here would have an answer or two . . .

    Can you spot the problem?


    The associated table with RPM, A/F, & HP can be found here as well:
    http://i11.photobucket.com/albums/a1...g?t=1163783180

    What the heck is going on?!?!?

    Here's some background:
    I originally had palnned on getting the car dyno tuned, but the guy who was doing the tuning wouldn't touch it because of the little hick-up in the HP curve (BTW, the guy who does the tuning knows how to tune - only works mainly on F-bodies & Vettes) . . . I also busted a push rod 2 months after I bought the car (missed the 2-3 shift, went 2-1 @ 5000 RPM in 2nd ). . . the car dealership replaced only the one broken pushrod, nothing else. The car has bad knock under load at low-mid RPM and at high RPM (cruising RPM is OK) & gets very poor gas mileage (around 14-15 MPG mixed). The tuner told me it was leaning out at the HP hick-up (aournd 5100 RPM) and he couldn't account for it (checked fuel pressure, replaced the plugs, swapped MAF - all were OK) . . .

    I'm on the last straw here and sick of having a sick SS.

    Any ideas would be awesome . . .
    Attached Files
    Last edited by meissen; November 17th, 2006, 12:48 PM.
    -Jason-
    2000 SS #1317
    QA-1:     Front & rear adj. shocks, front adj. coilover
    BMR: 1" rear springs, Adj. panhard, Adj. Lower Control Arms
    Spohn: Double Adj. torque arm w/sphirical rod ends & drive shaft loop (LTH model)
    Hotchkis: SFC, Strut tower brace
    SLP: Y-pipe, fan switch, TCS module, Air lid & bellows
    Pro 5.0: Pro 5.0 shifter w/Lou's short stick
    Borla: Adj. Catback
    ------------------------------------
    Clutch:
    McLeod - Kevlar disk w/billet steel Flywheel & adj. master cylinder
    Tires:
    Pirelli P-Zero Nero 275's on GM Chrome 10-spokes (street)
    Nitto Drag-radials on GM Painted 10-spokes (strip)



    Tags: automotive, bit, cars, cat, clean, collins, fear, fuel, graph, great, guy, helped, house, impressed, piston slap, pos, post, rear end, sea, sean, single, stop, stuff, things, tick, time, visit, waterford
  • #2
    What mods are done to the car? I've never seen an LS1 fall off like that. Mine pulls to ~5800 then starts to fall off slightly. It's no where near as drastic as yours is. Did the dealer inspect all the parts when they replaced the rod?

    _____________________________________________
    Wade
    2002 Camaro SS T Top Black M6 SLP 345HP
    1985 Camaro IROC Z28 T Top Silver 305TPI Auto
    2003 S10 Blazer 2 door 2wd 4.3 auto lowered 3" daily driver

    Comment

    • #3
      someone host the graph right on mifbody, i can't see it at work... if it's falling off and you broke a pushrod(valvetrain has been touched) I would bet money that it is valvetrain related... I've seen it happen quite a bit where the engine will break up at higher rpm... just host the graph...
      2010 Yukon Denali
      1999 Hugger Orange SS M6 - "M6 HOSS"

      Comment

      • #4
        Attached the graph in his first post.

        Honestly, I would say take it to Collins Automotive in Waterford, though I fear you might be a bit far from there. Sean is a great guy and knows his stuff, he's helped me with almost all of the cars in our house already, and I've ceased to stop being impressed by his knowledge every single time I go in there and visit.
        - Brian Meissen
        Owner, MiFBody.com
        Administrator, LTxTech.com


        1994 Camaro LT1 Transplant - 357ci LT1, cammed, stalled, and driven.
        2022 Camaro LT1 - "Cherry Bomb 2"
        Michigan FBody Meet & Greet Car Show 2022
        June 4th, 2022 - 9am to 3pm!!!
        The HUB Stadium, Auburn Hills, MI

        Comment

        • #5
          Originally posted by shiftinda93z
          someone host the graph right on mifbody, i can't see it at work... if it's falling off and you broke a pushrod(valvetrain has been touched) I would bet money that it is valvetrain related... I've seen it happen quite a bit where the engine will break up at higher rpm... just host the graph...
          Agreed, there's something else going on there. DETROITMUSCLE just had something very similar happen, and he ended up with a busted valve spring.

          I'd bet you have something similar going on.
          Originally posted by Redd8407
          I WANT NOISE! SPEED! AN ENGINE THAT SHAKES MY INTERNAL ORGANS LIKE THEY GOT PARKINSON'S! I DONT WANT AN ENGINE THAT IS PARTIALLY POWERED BY MY LAPTOP BATTERY!
          Originally posted by Z28ISGR8
          WHY THE F*CK IS THERE A GOAT ON A FERRARI?
          Originally posted by Darren
          I think it is because I take it in and out all the time, the rubber has just stretched out, especially at the bottom where it is really thin. It annoys me more then anything.

          Comment

          • #6
            Oh I would say 90% sure it's valvetrain related. Someone put up that table with A/F ratio too... Was he running a wideband O2 in one header, or at the tailpipe? leaning out is relative until i can see the #'s
            2010 Yukon Denali
            1999 Hugger Orange SS M6 - "M6 HOSS"

            Comment

            • #7
              Any mods done to the car and the HP/table are located here:
              http://www.cardomain.com/ride/377964

              Mods, page 1
              HP Curve/table, page 4
              -Jason-
              2000 SS #1317
              QA-1:               Front & rear adj. shocks, front adj. coilover
              BMR: 1" rear springs, Adj. panhard, Adj. Lower Control Arms
              Spohn: Double Adj. torque arm w/sphirical rod ends & drive shaft loop (LTH model)
              Hotchkis: SFC, Strut tower brace
              SLP: Y-pipe, fan switch, TCS module, Air lid & bellows
              Pro 5.0: Pro 5.0 shifter w/Lou's short stick
              Borla: Adj. Catback
              ------------------------------------
              Clutch:
              McLeod - Kevlar disk w/billet steel Flywheel & adj. master cylinder
              Tires:
              Pirelli P-Zero Nero 275's on GM Chrome 10-spokes (street)
              Nitto Drag-radials on GM Painted 10-spokes (strip)



              Comment

              • #8
                Originally posted by shiftinda93z
                someone host the graph right on mifbody, i can't see it at work... if it's falling off and you broke a pushrod(valvetrain has been touched) I would bet money that it is valvetrain related... I've seen it happen quite a bit where the engine will break up at higher rpm... just host the graph...
                Hmmm . . . I wonder if this is an exscuse to get some new heads . . . why not throw in a cam and LTs while I'm at it, eh?

                Is this as simple as replacing all the pushrods and checking the valve springs?
                Would a bent rod on an intake valve cause it to lean out? What about rod on an exhaust valve, same thing?

                I wasn't one of those guys who took autoshop in HS . . . I'm about 33% car savvy . . . I know the basics on how the engine works, thus my seemingly nieve nature.
                -Jason-
                2000 SS #1317
                QA-1:                 Front & rear adj. shocks, front adj. coilover
                BMR: 1" rear springs, Adj. panhard, Adj. Lower Control Arms
                Spohn: Double Adj. torque arm w/sphirical rod ends & drive shaft loop (LTH model)
                Hotchkis: SFC, Strut tower brace
                SLP: Y-pipe, fan switch, TCS module, Air lid & bellows
                Pro 5.0: Pro 5.0 shifter w/Lou's short stick
                Borla: Adj. Catback
                ------------------------------------
                Clutch:
                McLeod - Kevlar disk w/billet steel Flywheel & adj. master cylinder
                Tires:
                Pirelli P-Zero Nero 275's on GM Chrome 10-spokes (street)
                Nitto Drag-radials on GM Painted 10-spokes (strip)



                Comment

                • #9
                  Originally posted by balz2dwall
                  Would a bent rod on an intake valve cause it to lean out? What about rod on an exhaust valve, same thing?
                  Yes, it could, but I'd bet on a busted spring or two.

                  Pull the valve covers off and see what's there. That's a simple task. A busted spring should be pretty obvious.
                  Originally posted by Redd8407
                  I WANT NOISE! SPEED! AN ENGINE THAT SHAKES MY INTERNAL ORGANS LIKE THEY GOT PARKINSON'S! I DONT WANT AN ENGINE THAT IS PARTIALLY POWERED BY MY LAPTOP BATTERY!
                  Originally posted by Z28ISGR8
                  WHY THE F*CK IS THERE A GOAT ON A FERRARI?
                  Originally posted by Darren
                  I think it is because I take it in and out all the time, the rubber has just stretched out, especially at the bottom where it is really thin. It annoys me more then anything.

                  Comment

                  • #10
                    Originally posted by 81DaytonaPaceCar
                    Yes, it could, but I'd bet on a busted spring or two.

                    Pull the valve covers off and see what's there. That's a simple task. A busted spring should be pretty obvious.
                    I guess now that the SS gets to sleep for a couple of months, that might not be such a bad idea . . .

                    LOL! It's a good thing my finacee doesn't know about cars . . . I can make a broken spring or bent rod justification for some new heads.
                    -Jason-
                    2000 SS #1317
                    QA-1:                     Front & rear adj. shocks, front adj. coilover
                    BMR: 1" rear springs, Adj. panhard, Adj. Lower Control Arms
                    Spohn: Double Adj. torque arm w/sphirical rod ends & drive shaft loop (LTH model)
                    Hotchkis: SFC, Strut tower brace
                    SLP: Y-pipe, fan switch, TCS module, Air lid & bellows
                    Pro 5.0: Pro 5.0 shifter w/Lou's short stick
                    Borla: Adj. Catback
                    ------------------------------------
                    Clutch:
                    McLeod - Kevlar disk w/billet steel Flywheel & adj. master cylinder
                    Tires:
                    Pirelli P-Zero Nero 275's on GM Chrome 10-spokes (street)
                    Nitto Drag-radials on GM Painted 10-spokes (strip)



                    Comment

                    • #11
                      You say the motor has a knock? Can you tell if it's coming from the bottom end or top side of motor? Does it have a heavy sound or is it more of a tick? If it does have knock was it verified to be seen by the PCM? If so, that's what your problem is. PCM see's knock, down goes the timing and down goes HP.
                      sigpic
                      Turbo Charged LS1/T56

                      Comment

                      • #12
                        I don't think the engine knock is the cause of the horsepower hick-up . . . I think the detonation is being caused by whatever is causing the hick-up in the HP curve.

                        I used to have EFI Live (I traded it straight up for a set of GM chrome 10-spokes) and the timing retard from the knock sensors was present, but minimal. The HP curve is normal, maybe slightly retarded, but shows normal HP levels, if not higher than stock curves. I don't think timing retard is going to cut 100 horsies in a stretch of only 400-500 RPM.

                        I have a feeling that if it is something which has broken within the valvetrain that the valves effected by the breakage have caused carbon build up which is causing the detonation . . .

                        OK, now that I've been an adult about this whole deal, I'm gonna whine a little, now:
                        Darn it . . . I've had the car for 4 years now and I just got the Moser 12-bolt put in last year . . . I haven't been able to really open her up in a long time . . . I just want it to be fixed
                        -Jason-
                        2000 SS #1317
                        QA-1:                         Front & rear adj. shocks, front adj. coilover
                        BMR: 1" rear springs, Adj. panhard, Adj. Lower Control Arms
                        Spohn: Double Adj. torque arm w/sphirical rod ends & drive shaft loop (LTH model)
                        Hotchkis: SFC, Strut tower brace
                        SLP: Y-pipe, fan switch, TCS module, Air lid & bellows
                        Pro 5.0: Pro 5.0 shifter w/Lou's short stick
                        Borla: Adj. Catback
                        ------------------------------------
                        Clutch:
                        McLeod - Kevlar disk w/billet steel Flywheel & adj. master cylinder
                        Tires:
                        Pirelli P-Zero Nero 275's on GM Chrome 10-spokes (street)
                        Nitto Drag-radials on GM Painted 10-spokes (strip)



                        Comment

                        • #13
                          I broke a rocker arm once on my old TPI motor....ecm pulled out 30 degrees of timing becuase of the noise the sensor was picking up. Car had NO power because the ESC had taken all the timing away to try and curb the false knock. Not sure if the OBDII stuff on the LS1 works that way though.
                          sigpic
                          Turbo Charged LS1/T56

                          Comment

                          • #14
                            weak springs or valve train usually shows as a wavy graph.
                            knock? is it detonation or a rod knock/engine noise?
                            13.2 is not lean enough to cause issues.
                            what fuel are you using.
                            Last edited by 1BADAIR; November 17th, 2006, 04:14 PM.

                            Comment

                            • #15
                              It's typical that the dealership only replaced the one broken pushrod
                              I agree with the rest pull the valve covers replace all the pushrods and valvesprings and be done with it.
                              Ofcoarse I would do a cam swap at the same time, but thats just me.
                              Craig
                              Semi Retired Street Racer
                              2012 Lava Red Mustang GT 5.0 MT82
                              GONE BUT NOT FORGOTEN
                              sigpic
                              NBM `98 Formula M6 HdTp
                              1 of 1 Build Date 3/12/98

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