1. #1
    MJLiFe's Avatar
    MJLiFe is offline Junior Member
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    Stalling when revving down

    Hello all Iím new here and hope I can help some of you and vice versa. I have an 89 Comanche with a 4.0. The previous owner deleted most EVAP components which is giving me a headache. I have a stall issue when coming out of gear and engine is revving down. I cleaned throttle body, replaced plugs, wires, cap and rotor, fuel filter, air filter,and capped any existing vacuum lines. It also hesitates slightly when inducing throttle. Map sensor seems to be working fine because there is no misfire. Also battery sits at a healthy 12.5V and 14.7V when running. But still dies after revved up high just canít keep steady idle. Any thoughts would be greatly appreciated thanks again.

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    Re: Stalling when revving down

    Update. I narrowed it down and will be readjusting the TPS some time this week hoping that this will fix the issue I will update again when Iím done if there are any other ideas I would greatly appreciate the input. Thanks


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    JPNinPA's Avatar
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    Stalling when revving down

    What do you idle at before revving?

    Have you measured fuel pressure?

    Are the plugs wet after stalling?

    IAC is dirty


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    Re: Stalling when revving down

    It idles around 1200. Plugs are not wet after stalling. Cleaned IAC and had no change. Have not measured the fuel pressure yet but will do that thanks so much.


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    Stalling when revving down

    So you air/vac leak and not a fuel issue.
    Check for an intake leak or a vac line leak.
    Idle should be ~750 rpm


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    Last edited by JPNinPA; 12-05-2019 at 10:32 PM.
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    Re: Stalling when revving down

    Great thanks again this weekend I will check all vacuum lines. I already removed throttle body cleaned and replaced gasket. Will update on progress.


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    Re: Stalling when revving down

    Start it and let it idle. Take WD40 or carb cleaner and spray around intake area then all vac lines. Injectors and plugs. When the idle changes or shudders from the spray you found the leak. Post back if you done.

    Of course these are flammable, so no open flame and donít let the engine get hot.


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    Re: Stalling when revving down

    Gotcha thanks I will run that test tomorrow. As for the TPS Iím getting 4.98V going in and no reading on the signal side so also trying to track that issue. Again thanks and will update results tomorrow.


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