Anonymous
Anonymous asked in Cars & TransportationMaintenance & Repairs · 1 month ago

Cold car struggles accelerating?

My Grand Marquis 2005 struggles accelerating when I first start the car in the morning. Once temp reaches it's optimum level after like 10-15 minutes, car then accelerates and shifts smooth. When accelerating cold car, suddenly acceleration drops for a second and car struggles like it's going uphill and (it feels same as when car breaks traction and acceleration stops) comes back on fine by itself. Today when I was standing at red light and when green light came on, I pressed the gas pedal but car started struggling and would move barely and suddenly started accelerating fine. It feels same as when car is in limp mode. Last week I got rear freeze plug of engine replaced which needed tranny to be removed. After installing tranny back and starting the engine, car went into limp mode with wrench and overdrive light on and car struggled the same way but this time it was constantantly. I had to remove negative terminal on battery for 10 minutes and after that car started fine and been running fine but this struggle for second on cold start is still there. Only code stored is for O2 sensor heater malfunction. Tranny was rebuilt 5 years ago by previous owner.

Update:

Tranny fluid level is fine.

5 Answers

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  • Anonymous
    1 month ago

    believe it or not - had the same behaviour with the faulty speedo, when it was feeding crazy readings to the ECU when cold.

  • Anonymous
    1 month ago

    Fix the O2 sensor heater code.  Car is not going into "closed loop" mode and is running rich until the O2 sensor is hot.

  • Anonymous
    1 month ago

    1) Check for a faulty coolant temperature sensor or simply replace it. Not expensive.

    2) Look for any type of intake vacuum leak, positive crankcase ventilation (PCV) valve issue or an air leak downstream of the mass air flow (MAF) sensor..3) If those aren't the cause, then get a diagnostic done from a Ford / Mercury garage. Itt may be caused by a faulty powertrain control module (PCM) commanding an erratic signal to the exhaust gas recirculation valve (EGR) stepper motor. If diagnostic testing confirms an erratic signal, replace the PCM.

  • 1 month ago

    Have you checked the transmission fluid level?

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  • Anonymous
    1 month ago

    Bad upstream O2 sensor

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