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Reason for unable to rev beyond...

Discussion in '308/328' started by Crowndog, Aug 1, 2020.

  1. Crowndog

    Crowndog F1 Veteran
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    #1 Crowndog, Aug 1, 2020
    Last edited: Aug 1, 2020
    4800 rpm. Any ideas? My first thoughts:

    Broken throttle position switch (no wot signal) I only hear one click turning the throttle through full range. I think it should have 2

    Fuel pressure regulator not working correctly

    Vacuum leak

    What do you think? Also no high speed idle at cold start.

    Any suggestions are welcome. This is a 4 valve injected 308
     
  2. Smiles

    Smiles Moderator
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    But you do have full power?

    Matt
     
  3. Crowndog

    Crowndog F1 Veteran
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    No. It only revs to 4800rpm but does it well up to that point.
     
  4. Smiles

    Smiles Moderator
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    Then I don't know. Interesting.

    Matt
     
  5. Crowndog

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    I will add that almost all vacuum lines are original braided covered.
     
  6. kiwiokie

    kiwiokie Formula Junior

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    Cat or no cat?


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  7. Crowndog

    Crowndog F1 Veteran
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    Cat
     
  8. mike996

    mike996 F1 Veteran

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    Did this behavior begin abruptly or has max RPM been gradually decreasing? Is the max RPM the same regardless of engine load, same 4800 RPM max whether accelerating in neutral or on the road in gear?
     
  9. kiwiokie

    kiwiokie Formula Junior

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    Plugged cat?


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  10. Steve Magnusson

    Steve Magnusson F1 World Champ
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    No, the idle switch has an audible click, but the WOT switch is a (soundless) pair of contacts (closed by a cam) that allows over-travel:

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    Have you put a timing light on it to confirm/deny you aren't losing a bank of ignition?

    Also, is the warm idle unchanged (i.e., it's still the same as it was when it would rev over 4800 RPM)?
     
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  11. Crowndog

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    Mike it was gradually
     
  12. Crowndog

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    Thank you for the clarification.
    No timing light test....yet
    Yes
     
  13. Crowndog

    Crowndog F1 Veteran
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    The engine in question is in a Mondial 3.2
     
  14. mike996

    mike996 F1 Veteran

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    If it occurred gradually, it could very well be muffler or cat breaking down internally/clogging as was suggested earlier. I've worked on cars with mufflers or cats so badly clogged that the engine could only idle - no power available above that.
     
  15. AUDIO RESEARCH

    AUDIO RESEARCH Formula Junior

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    What happens when the engine reaches 4,800 RPM , is there some sort of a misfire , or lost of power ? This happened to my 3.2 Mondial when the new Bosch Fuel Pump I installed was from a Mercedes 280SE . Idling and power was perfect but when it reach 5000 RPM misfiring and lost of power . When I installed the proper Bosch fuel pump for the Mondial problem solved .
     
  16. miketuason

    miketuason F1 World Champ
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  17. mike32

    mike32 F1 Rookie

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    Is this 4800 max in any gear or just in top ? Fuel filter will limit revs in top if getting dirty
     
  18. Albert-LP

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    I had the same problem with both my 208 turbo: it happened around 5500 rpm in one and around 5000 rpm in the other. Solved with a full service to the Bosch fuel distributor: I was told that the membrane there is inside makes a frequency resonance due to age hardening. Both happened when they were around 33-34 years old

    It was like hitting the a rev limiter

    Ciao
     
  19. spicedriver

    spicedriver Formula 3

    Feb 1, 2011
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    No high speed idle is likely an AAV stuck closed. You can loosen it up by spraying a lubricant inside, and work the valve back and forth with a screwdriver. This would not cause the lack of revs problem.

    I would check for proper fuel pressures there.
     

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