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i have mazda 3 2008 with auto transmission.

after drive for 10-15 mintues the rpm get lagging. (when the lag start i lost a little performance on car :: pushing the pedal the rpm goes to 4000 but after a sec goes to 3700 without change the pressure on gas pedal)

Visit https://www.youtube.com/watch?v=frEQPNeFoYA for check the video of this lag!

if i turn off the car for while the lag gone. but it become again after a long drive)

  • i change the cylinder head but problem not solved.
  • no error code.
  • battery replaced
  • i cleaned the throw body + MAF
  • my mechanic said he cleaned the EGR too. but i'm not sure. it could be from there?

Q1: do i need to replace the MAF or MAP sensor? ( no ODB error code )

Q2: could it be from transmission?

Q3: WHAT ABOUT KNOCK SENSOR?

this problem made me mad.

UPDATE -> i change the knock sensor/o2 sensor but no luck.

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    Welcome to Motor Vehicle Maintenance & Repair! Could you clarify the statement "i change the engine but problem not solved" ... You actually swapped the engine out? Commented Oct 8, 2018 at 11:09
  • i just change the cylinder head not the whole engine.
    – Mostafa
    Commented Oct 8, 2018 at 23:01
  • You say it goes down by 300, but in the video I see the rpm go down to idle speed. What is the clip showing actually? Is the rpm dropping while you hold the pedal at the same angle?
    – luntain
    Commented Oct 25, 2018 at 9:26
  • Before you start replacing sensors, connect a computer and see what the sensors show.
    – luntain
    Commented Oct 25, 2018 at 9:32

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Finally i found the problem. all the problem came from bad gauge Cluster :O

the official dealership replace my torque cluster and everything work perfect after the replacement

i bought the car for 60k and spend 20k for diagnosing jerking rpm.

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  • i still don't know whats the connection between lost performance and display gauge.
    – Mostafa
    Commented Nov 4, 2018 at 21:43

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