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    #1

    Car hesitation

    Have a hesitation issue that feels like a worn clutch. Noticed this over the years, especially following maintenance and repairs where ignition harness + MAF disconnected. Upon start up following those, car is very peppy and then dials down the power. Feeling is akin to sport mode on and off, however sport mode does nothing for this hesitation. This was extremely noticeable when for the first 300 miles following my engine rebuild where the car just felt like something I've never experienced before, so alive and peppy. Could engage clutch (new) and the torque of the motor just moved the car. I am making a stink of this now, because following winter storage, the hesitation is frankly worse. Reversing on clutch the engine stalls out. Power steering at low speeds bogs down the motor. Honestly feels like running at 10% reduced power.

    Now, the engine rebuild was 10k miles after I replaced coils, spark plugs, fuel filter, went catless euro headers (no downstream o2 sensor), pretty much up to date on everything within last 15k miles.

    I realize its either a fuel, spark, or air issue but nothing I can easily think of. I guess I'm looking for an easy way out here without throwing more money at the car. Anyone experienced something similar? Need to get this sorted ahead of springtime mods.
    Tags: None
    #2
    So any action you perform with the car bogs the engine? Did you replace your pulleys and tensioner at some point in time? How bad do the rpms dip?

    Comment

      #3
      Yes everything replaced 5k miles ago with rebuild of motor. In normal driving no bogging but in actions like reversing with steering inputs will stall the vehicle.

      Comment

        #4
        Vacuum leak test with a smoke machine and compression test might be a good/easy place to start.

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          #5
          Compression test 155/160 across all cylinders. Will look into smoke test thanks

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            #6
            Your compression done on a warm engine? 155-160 is actually below spec...

            Sent from my SM-G950U using Tapatalk

            Youtube DIYs and more

            All jobs done as diy - clutch, rod bearings, rear subframe rebush, vanos, headers, cooling, suspension, etc.

            PM for help in NorCal. Have a lot of specialty tools - vanos, pilot bearing puller, bushing press kit, valve adjustment, fcab, wheel bearing, engine support bar, etc.

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              #7
              Originally posted by mrgizmo04 View Post
              Your compression done on a warm engine? 155-160 is actually below spec...

              Sent from my SM-G950U using Tapatalk
              Yes they do look low ideal spec is around 175 psi


              Sent from my iPhone using Tapatalk Pro

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                #8
                Leaking valve cover... does this count as vacuum leak?

                Comment

                  #9
                  Originally posted by Kdubski View Post
                  Leaking valve cover... does this count as vacuum leak?
                  Not really. You are mostly looking for a leak in the intake system, ICV, air rail or vacuum lines.

                  Comment

                    #10
                    Were adaptations reset after? How does the car drive in higher rpms. If it happens only at idle id look into the idle air control valve being stuck, or like others mentioned a vacuum leak. Could also be a faulty maf or o2 sensor

                    If you can data log all sensors when this happens that will help narrow down your search


                    Last edited by Lukem3; 04-06-2021, 10:46 PM.

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                      #11
                      Originally posted by Slideways View Post

                      Not really. You are mostly looking for a leak in the intake system, ICV, air rail or vacuum lines.
                      Yes it does, but on these engines i have yet to see it cause issues. They all leak unless they were just replaced. Also compression looks fine, with the vanos timing on these it's always lower than what you would expect to get. Plus they're all even, and u said everything's fine after maf unplug. So mechanically everything is going to be okay. You're looking at an air problem(restriction or excess) , lack of fuel, idle control, ignition fault or a sensor.

                      If the leak is bad enough on the back end it could have shorted the cam sensor or wiring.

                      Sent from my SM-G955U1 using Tapatalk

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                        #12
                        Originally posted by Kdubski View Post
                        catless euro headers (no downstream o2 sensor).
                        Are you running O2 sensors in the headers?

                        Edit: Ignore my stupid question *facepalm*
                        Last edited by Syfon; 04-07-2021, 12:57 AM.

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                          #13
                          Originally posted by Lukem3 View Post
                          Yes it does, but on these engines i have yet to see it cause issues. They all leak unless they were just replaced. Also compression looks fine, with the vanos timing on these it's always lower than what you would expect to get. Plus they're all even, and u said everything's fine after maf unplug. So mechanically everything is going to be okay. You're looking at an air problem(restriction or excess) , lack of fuel, idle control, ignition fault or a sensor.

                          If the leak is bad enough on the back end it could have shorted the cam sensor or wiring.

                          Sent from my SM-G955U1 using Tapatalk
                          Yes, you're right on the money. Appreciate your run down of what it may be. When I take apart the front end (everything involved for say valve cover job for example) the first few hundred miles are excellent. Car is peppy and has no hesitation. It seems like something is "reset". Now I am thinking it's either air, ignition, or possibly O2 related.

                          Do you have any software recommendations for data logging?

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