2008 trailblazer 4.2

Collapse
X
 
  • Time
  • Show
Clear All
new posts
  • BRIAN617
    Senior Member
    • Dec 2016
    • 153

    2008 trailblazer 4.2

    Anyone have a good cam/crank scope trace I can look at please?
  • SnapOnKid
    Senior Member
    • Jan 2011
    • 870

    #2
    Whats the issue your haveing?

    Comment

    • BRIAN617
      Senior Member
      • Dec 2016
      • 153

      #3
      Basket case. Questionable "rebuilt" engine installed by who knows and hasn't started since install. Been to three shops already, all with different diagnoses. I suspect its out of time. I scoped cam and crank and none of the rising/falling edges align. Fairly big job to pull valve cover and confirm.

      Comment

      • Matt
        Senior Member
        • Dec 2008
        • 328

        #4
        Cranks-no-start I'm guessing? Cam/Crank correlation fault codes? Compression test results?

        Comment

        • SnapOnKid
          Senior Member
          • Jan 2011
          • 870

          #5
          Yeah but from what I recall you can't see the bottom timing mark on the crank. And you have to remove the oil pan in order to remove the front timing chain cover.
          Which basically means engine out on this model...

          It's interesting that someone installed a rebuilt motor that won't start and it's been to 3 different shops with 3 different Diagnoses.

          What failed on the original engine that required a replacement?
          No one from the other 3 shops wanted to work on it?
          Owner doesn't want to spend any more money?

          As mentioned any other diagnostics like compression test been performed? Any Codes?

          Comment

          • BRIAN617
            Senior Member
            • Dec 2016
            • 153

            #6
            Originally posted by Matt
            Cranks-no-start I'm guessing? Cam/Crank correlation fault codes? Compression test results?
            No codes, battery has been dead too long.

            Comment

            • BRIAN617
              Senior Member
              • Dec 2016
              • 153

              #7
              Originally posted by SnapOnKid
              Yeah but from what I recall you can't see the bottom timing mark on the crank. And you have to remove the oil pan in order to remove the front timing chain cover.
              Which basically means engine out on this model...

              It's interesting that someone installed a rebuilt motor that won't start and it's been to 3 different shops with 3 different Diagnoses.

              What failed on the original engine that required a replacement?
              No one from the other 3 shops wanted to work on it?
              Owner doesn't want to spend any more money?

              As mentioned any other diagnostics like compression test been performed? Any Codes?
              I get lots of mystery stuff like this.
              Don't have any history or explanations.
              Plus I don't want to waste anymore of my time if they aren't willing to pay to fix.

              Comment

              • BRIAN617
                Senior Member
                • Dec 2016
                • 153

                #8
                Mystery solved! Finally found a cam crank pattern on google images, however it was for an 05 model. My 08 pattern matches it perfectly so the engine is timed properly. Problem is 08 uses different reluctor wheel.

                Comment

                • Matt
                  Senior Member
                  • Dec 2008
                  • 328

                  #9
                  Originally posted by BRIAN617
                  Mystery solved! Finally found a cam crank pattern on google images, however it was for an 05 model. My 08 pattern matches it perfectly so the engine is timed properly. Problem is 08 uses different reluctor wheel.
                  Tell them to hand over some cash before you can do anymore diag

                  Comment

                  • BRIAN617
                    Senior Member
                    • Dec 2016
                    • 153

                    #10
                    Interesting tidbits of data PID info for future reference.

                    While cranking Cam and Crank PIDs show RPM, however engine RPM PID shows zero. Also no coil trigger from PCM.

                    The engine in this vehicle had 7 tooth crank reluctor.
                    The 2008 model is supposed to have 58.

                    Comment

                    • dgsnap
                      Junior Member
                      • Nov 2009
                      • 23

                      #11
                      Hi,

                      I found this site not long ago has lots of ckp/cam correlation
                      scope patterns inc Trailblazer. https://rotkee.com/en/waveform-library?system=51

                      Cheers

                      Comment

                      • BRIAN617
                        Senior Member
                        • Dec 2016
                        • 153

                        #12
                        Thanks for that link!

                        Comment

                        Working...