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  • High idle speed

    I drove the coupe back from Warwickshire yesterday and the tick over on start up was around 1200 rpm but only dropped to 800 when warm (600 normally) it did at times drop down to 600 but mainly a steady 800? throttle cable appears good and linkage seams to work freely. Any idea's?

  • #2
    Aircon on ?

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    • #3
      Originally posted by kwoffa View Post
      Aircon on ?

      no - air con was off

      Comment


      • #4
        That runner pipe thingy under the intake plenum?
        2002 '52 S54 - Titanium Silver with 18" BBS LMs, AP Racing BBK, KW V3, H&R anti roll bars & ACS flippers (previously 2000 'X' S50 - Arctic Silver)

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        • #5
          Originally posted by Spooks View Post
          That runner pipe thingy under the intake plenum?
          I did replace it a couple of years ago but yes its worth a look

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          • #6
            I get this from time to time also. Tends to be after the car has rested for 12+ hours after a long run. Initial start-up 1200rpm, eventually settles around 800rpm, then later in the drive it's back down to 600rpm and next start-up is normal.

            Appreciate that's of no use to you what so ever Dave, but watching this thread with interest
            Not actually in the least bit fat

            2000 S50 Titanium Silver / Black
            ACS Suspension, Exhaust & Type III Wheels
            Simota carbon air intake | Strong Strut Front Brace

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            • #7
              Originally posted by Fat Tony View Post
              I get this from time to time also. Tends to be after the car has rested for 12+ hours after a long run. Initial start-up 1200rpm, eventually settles around 800rpm, then later in the drive it's back down to 600rpm and next start-up is normal.

              Appreciate that's of no use to you what so ever Dave, but watching this thread with interest
              I spoke to Darren Woods and asked if it was a known problem but he hasn't come across it before but he said it was worth oiling the throttle linkage bar and springs as it may be that not coming back to rest fully.

              Comment


              • #8
                Similar problem on this thread,

                http://www.z3mcoupe.com/forum/showthread.php?t=17805

                Comment


                • #9
                  In my S50 when the Vanos was starting to fail the first symptoms were varying idle and especially higher than normal idle (around 800-900 rpm) even when engine was fully warm. At this point the idle was not in any way "rough" neither the engine showed any other symptoms of running poorly.
                  No external leaks in the Vanos either. Also the magnetic valves were working ok. Most likely the Vanos internal piston seals were already compromised and there was internal loss of working pressure.

                  The idle issues were highlighted when AC was on but the idle was raised also by simply turning the steering wheel when the car was not moving (and AC off). The power steering pump starting to take some power was enough to cause the idle to be raised. Waiting for 30 secs after car came to stop was enough to slowly return the idle to normal.

                  After Vanos fix (replacing the whole unit) these idle issues disappeared.

                  But however, this was for S50 with different type of Vanos.

                  br, Juha
                  The older I get, the faster I was ...
                  BMW HP2 Sport
                  ex- BMW Z3 M Coupe - Cosmosschwartz Metallic

                  Comment


                  • #10
                    Originally posted by JuhaV View Post
                    In my S50 when the Vanos was starting to fail the first symptoms were varying idle and especially higher than normal idle (around 800-900 rpm) even when engine was fully warm. At this point the idle was not in any way "rough" neither the engine showed any other symptoms of running poorly.
                    No external leaks in the Vanos either. Also the magnetic valves were working ok. Most likely the Vanos internal piston seals were already compromised and there was internal loss of working pressure.

                    The idle issues were highlighted when AC was on but the idle was raised also by simply turning the steering wheel when the car was not moving (and AC off). The power steering pump starting to take some power was enough to cause the idle to be raised. Waiting for 30 secs after car came to stop was enough to slowly return the idle to normal.

                    After Vanos fix (replacing the whole unit) these idle issues disappeared.

                    But however, this was for S50 with different type of Vanos.

                    br, Juha

                    Interesting stuff, I will try it with the a/c on and see what happens. Mine is also S50 with replacement vanos by BMW in 2005

                    Comment


                    • #11
                      Checked rubber bung which is fine also oiled throttle linkage and springs, checked throttle cable and cruise cable all look ok. Engine starts at around 1200rpm on fire up and then dropped down to 600rpm when warm.
                      A/C on or off and steering turning makes no difference to revs. Will keep an eye on it and see if it happens again.




                      Comment


                      • #12
                        Hello Dave,

                        That is good news.

                        I think there are many possible reasons to have an slightly elevated, higher than normal idle in some situations without having any real engine issues. For example, after longer period of continuous hard driving it seems that my car takes a little longer (20 sec or so) to settle down into normal 600-700 rpm idle. Again, if the outside temperature is somewhere between + 5-10 C it seems that finding the correct idle when warming up the engine takes somewhat longer than in lower or higher outside temperatures. Might be related to some short term adaptive values in the DME/ECU ?

                        Regarding the Vanos issue that I described earlier in this thread, my theory is the following below. I have not yet checked this out by disassembling the old unit that is still on my workdesk at the garage. Intend to do so at some point.

                        I believe that when the internal Vanos piston seals deteriorate to certain level, they will start leaking internally which will slow down the response time of Vanos when changing the camshaft positions. This will happen especially near idle where the output of the Vanos oil pump will be lowest. The feedback from the camshaft position sensors helps the system to compensate for these leaks and the system will try to drive the camshafts towards the target positions but the delays will eventually start to grow and at some point the target positions cannot any more fully reached near idle with low pump outputs. This makes the idle to start to wander around and at certain point will start to cause rough running.

                        This could be tested/found out by making the Vanos test where test computer shifts the Vanos and camshaft timings around and measures both the response times and difference between the actual and target camshaft positions. This will reveal also the internal leaks in the Vanos pistons or if the Vanos oil pump cannot produce enough pressure at idle. I did not have this capability so I have no data to show about this.

                        My current Vanos is an original factory (Rolls-Royce ?) serviced unit and it worked beatifully the first 20 000 km but already shows some slight signs of fatigue. All other seals are OEM except the solenoid O-rings which I changed into the M5 version at about first 10000 km when the original type seals started to generate a slight external leak. The next Vanos unit will be most likely prepared from my original unit and it will rather likely not use original seals in order to improve the long term reliability of these thingys.

                        That having been said, I have been lately driving some first generation water-cooled 911's equipped with the 3.4 liter engine. Thanks to Vanos, our cars feels much more responsive in the low rpm range than those Porsches :) The Vanos really helps and therefore so some challenges to live with it are easier to tolerate.

                        br, Juha
                        Last edited by JuhaV; 17-08-2016, 07:17 AM. Reason: some typos and clarifications
                        The older I get, the faster I was ...
                        BMW HP2 Sport
                        ex- BMW Z3 M Coupe - Cosmosschwartz Metallic

                        Comment


                        • #13
                          Originally posted by JuhaV View Post
                          Hello Dave,

                          That is good news.

                          I think there are many possible reasons to have an slightly elevated, higher than normal idle in some situations without having any real engine issues. For example, after longer period of continuous hard driving it seems that my car takes a little longer (20 sec or so) to settle down into normal 600-700 rpm idle. Again, if the outside temperature is somewhere between + 5-10 C it seems that finding the correct idle when warming up the engine takes somewhat longer than in lower or higher outside temperatures. Might be related to some short term adaptive values in the DME/ECU ?

                          Regarding the Vanos issue that I described earlier in this thread, my theory is the following below. I have not yet checked this out by disassembling the old unit that is still on my workdesk at the garage. Intend to do so at some point.

                          I believe that when the internal Vanos piston seals deteriorate to certain level, they will start leaking internally which will slow down the response time of Vanos when changing the camshaft positions. This will happen especially near idle where the output of the Vanos oil pump will be lowest. The feedback from the camshaft position sensors helps the system to compensate for these leaks and the system will try to drive the camshafts towards the target positions but the delays will eventually start to grow and at some point the target positions cannot any more fully reached near idle with low pump outputs. This makes the idle to start to wander around and at certain point will start to cause rough running.

                          This could be tested/found out by making the Vanos test where test computer shifts the Vanos and camshaft timings around and measures both the response times and difference between the actual and target camshaft positions. This will reveal also the internal leaks in the Vanos pistons or if the Vanos oil pump cannot produce enough pressure at idle. I did not have this capability so I have no data to show about this.

                          My current Vanos is an original factory (Rolls-Royce ?) serviced unit and it worked beatifully the first 20 000 km but already shows some slight signs of fatigue. All other seals are OEM except the solenoid O-rings which I changed into the M5 version at about first 10000 km when the original type seals started to generate a slight external leak. The next Vanos unit will be most likely prepared from my original unit and it will rather likely not use original seals in order to improve the long term reliability of these thingys.

                          That having been said, I have been lately driving some first generation water-cooled 911's equipped with the 3.4 liter engine. Thanks to Vanos, our cars feels much more responsive in the low rpm range than those Porsches :) The Vanos really helps and therefore so some challenges to live with it are easier to tolerate.

                          br, Juha

                          I did feel at least a couple of times over the weekend the car felt not 100% and the power delivery on occasion was stepped and not smooth so may be signs of a vanos issue.

                          Comment


                          • #14
                            I had a similar issue Dave but would also present itself with intermittent high idle hot or cold. Eventually located to the throttle bodies having developed a gum line around the butterfly valves causing them not to close properly. I can only presume this was a result of little use but after stripping them down and a good clean all was back to normal.
                            Aceman

                            Arctic Silver Z3MR

                            Rocking seats ? You need seat bushes click HERE
                            ///M Badge Refurb available HERE

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                            • #15
                              Is the idle fluctuating and stuttering? Any signs of an air leak in the intake rubber?
                              Last edited by Rags; 18-08-2016, 12:34 PM. Reason: Typo

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