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Thread: Flat Spot between 3-4000rpm when hot.

  
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    anti-miracle-man's Avatar
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    Flat Spot between 3-4000rpm when hot.

    Hi guys... Im from South Africa. Drive a Astra G OPC
    its a Z20LET engine...

    Engine is stock.. but i have this flat spot... When i start the car early in the morning, and i wait for the engine to warm up... it runs perfect! very strong.. But when it goes over to the running map.. +- 70deg cel. then i have this flat spot between 3000 - 4000 rpm... after 4000rpm it pulls like a deamon again!

    I have replaced a AFM about 6months ago. After a bodyshop damaged my afm by starting the car in the Hot bake oven after a quick paint patchup. Had to get a used AFM to clear the Error code.

    I dont think it is boost related.. the turbo still spins at the same speed. Just the flat spot. Im thinking AFM or O2 sensor? Please advice needed

    Regards
    Anti

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    bereet's Avatar
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    I'd say afm due to me having same issues recently after putting a friends afm and resetting battery all was good.
    SILVER ASTRA GSI RUNNING . . . . . . . HA HA THAT WOULD BE TELLING

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    it will be afm,boost solenoid or plugs gauranteed
    God bless turbos!!!!

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    try the above and change your fuel filter aswell!
    GSi

    Built not Bought

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    thanks guys, havent had alot of time to look into the engine as im buzy with a HUGE jl audio custom fiberglass install in the trunk... plus my girlfriends needs attention .....

    So i changed the AFM about a few months ago as explained... it ran fine for a few 100 km and then it went to the flat spot again... how come the AFM is so sensitive in our cars.. If i would wanna go for a wider range AFM or a ECU chip to fool the ECU how can i go about that ? My understanding on the AFM and ECU is that it is very very sensitive... meaning the AFM doesnt give out a very accurate reading to the ECU... Any upgrade parts available.... Plugs has been changed recently btw


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    Are you running an aftermarket filter??? It seems that those running K&N style oiled filters have a lot of problems with the AFM's.

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    hey Aussie, no aftermarket filters... everything is dead stock on the engine... filters the works stil the same as the factory ones
    Kicking ur ass.... the OPC way..

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    Front BCS mate, try that one and i'l bet that is the problem
    Astra Coupe Z20LET EDS stage 2


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    mick n em's Avatar
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    replace bcs

    hi, sorry to hijack, are you suggesting the front bcs should be replaced, im curious as im experiencing a flat spot in my zafira that ive had since saturday
    mick

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    Thumbs Up

    Hi guys... just a quick update.. Yesterday i took off my front BCS.. sprayed it out with electronic switch clear with lube... I took the car for a drive... I noticed that for a few times the car just started pulling hard.. like a big surge of power... It then smoothed out... its now pulling much smoother.... there is still a bit of hessitation from the engine but i recon the ECU adapted the map to the "faulty bcs"... Alot of crap came out the BCS... Another 100km or so and i recon the ECU will smooth out and my flat spot will be a thing of the past... I still think the AFM might be a factor also but cleaning the BCS did help for me!!! thanks for the help so far...
    Driving to work this morning was fun Much smoother indeed! Lets hope it lasts
    Kicking ur ass.... the OPC way..

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