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  • Question : Interesting 3.1 Hesitation, Suggestions?

    Fellow 60 degreers,
    Got an interesting problem, here's the details:

    99 Cutty, 3.1, 151,xxx miles.

    Over the last month or so I've been fighting this hesitation issue. When the car is physically in gear (drive or reverse) I get this intermittent hesitation, especially at idle. Hesitation is only present very low in the RPM band (idle-1700). Above 17/1800 it disappears. Note that there is no hesitation at all while the car is in park or neutral regardless of RPMs.

    Changed all the seemingly normal culprits: plugs and wires, coils, ICM, TPS, IAC, cleaned out the throttle body, etc. Checked extensively for vacuum leaks and replaced anything that looked suspect. Checked vacuum at the intake ports (inHg) which seemed pretty constant with no crazy fluctuations. All have produced no positive impact on the problem.

    For the most part ECM flashes no codes, occasionally I'll get a "303" (cylinder 3 misfire) or 300 (random misfire) code that doesn't illuminate the service engine light.

    Haven't checked anything with the fuel system yet, probably my next step.

    Anyone have any suggestions at what I should be looking for here? Any input would be greatly appreciated, I'll follow up once the problem is solved.

    Thanks!

  • #2
    Have you ever changed oxygen sensors? They won't cure a misfire, but could help the hesitation and improve fuel economy.

    Sent from my HTC One X using Tapatalk 2
    -60v6's 2nd Jon M.
    91 Black Lumina Z34-5 speed
    92 Black Lumina Z34 5 speed (getting there, slowly... follow the progress here)
    94 Red Ford Ranger 2WD-5 speed
    Originally posted by Jay Leno
    Tires are cheap clutches...

    Comment


    • #3
      I'm thinking it may be the sensor It controls fueling etc. from idle to 2000 rpm ,then kicks into batch fire

      Comment


      • #4
        Thanks for the responses.

        As far as the 02 goes, I think the cutty has 2 of them, upstream and downstream. I probed the upstream sensor and it seems to have the proper resistance. Does the downstream sensor have as big a part as the upstream does? Could the sensor be bad even though the resistance seems good and the ECM isn't throwing any codes about it?

        Thanks!

        Comment


        • #5
          The upstream is the one responsible for fueling. The downstream is used to let pcm know the cat is doing its thing.

          They can still read good resistance wise, but they react slower as they age. It's still working or else you would be getting a code, but not as well as it should. IIRC, the change interval on them is 50-60k miles.

          Sent from my HTC One X using Tapatalk 2
          -60v6's 2nd Jon M.
          91 Black Lumina Z34-5 speed
          92 Black Lumina Z34 5 speed (getting there, slowly... follow the progress here)
          94 Red Ford Ranger 2WD-5 speed
          Originally posted by Jay Leno
          Tires are cheap clutches...

          Comment


          • #6
            Appreciate the input, gonna give the upstream sensor a try tomorrow and see what that leads too. I'll keep the updates coming as it gets worked out.

            Comment


            • #7
              Actually i meant the crank sensor and or cam sensor

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              • #8
                Once again thanks for the input guys.

                Unchained, I was thinking crank or cam sensor, both i believe are originals and could be viable options. Is it possible to probe both sensors first and test them prior to removal?

                O2 is still a possibility as well although less likely as its been changed under a year ago.

                The search continues...

                Comment


                • #9
                  Unchained,
                  Forgot to add, there are two crank sensors (24x and 7x), 24x behind the crank pulley 7x on the back of the block. Should I change em both or is one more suspect then the other?

                  Comment


                  • #10
                    The one on the "back" is easy to change. That is if you have small arms and a 1/4 drive ratchet.
                    You will have to pull the balancer to get to the 24x.
                    95 Beretta 3100 with 3400 intakes and TCE TB
                    High flow cat and a Magnaflow muffler
                    Grand Prix trans with 3.33FDR

                    Comment


                    • #11
                      The one on the back is the 7x sensor, if that one goes and the engine stops. The 24x isn't required for engine operation. It's used for sfi mode.

                      Sent from my HTC One X using Tapatalk 2
                      -60v6's 2nd Jon M.
                      91 Black Lumina Z34-5 speed
                      92 Black Lumina Z34 5 speed (getting there, slowly... follow the progress here)
                      94 Red Ford Ranger 2WD-5 speed
                      Originally posted by Jay Leno
                      Tires are cheap clutches...

                      Comment


                      • #12
                        That is my point pocket rocket. It controls fueling from idle to 2000 rpm.

                        Comment


                        • #13
                          Yeah, I was just letting him know if the 7x goes the car won't run so there's no point in changing it.

                          Sent from my HTC One X using Tapatalk 2
                          -60v6's 2nd Jon M.
                          91 Black Lumina Z34-5 speed
                          92 Black Lumina Z34 5 speed (getting there, slowly... follow the progress here)
                          94 Red Ford Ranger 2WD-5 speed
                          Originally posted by Jay Leno
                          Tires are cheap clutches...

                          Comment


                          • #14
                            Hey Everyone,
                            I know its been a while since my last post, just wanted to float an update out there and ask for some more advice.

                            Got around to changing out the 24x sensor and the cam sensor, both produced no results. Here's a list of what's been done to the car in the past 2 or so months to try to fix this problem.

                            Spark plugs, wires, ignition coils, ignition module, EGR, TPS, IAC, 24x crank sensor, cam sensor.

                            Problem however still exists, getting rough hesitation at idle and anything under 2000 rpm. Seems as if all the fixes I've done are having no effect as the hesitation is getting worst. ECM occasionally shows a P0300 code (random/multiple cylinder misfire).

                            So any ideas out there? What's my next step?

                            Suggestions appreciated tremendously

                            -DaAPKGodfather

                            Comment


                            • #15
                              Dirty MAF? LOL stumped. Coolant temp sensor?
                              95 Beretta 3100 with 3400 intakes and TCE TB
                              High flow cat and a Magnaflow muffler
                              Grand Prix trans with 3.33FDR

                              Comment

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