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Q: Cold engine problems

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My car has an automatic transmission. Lately, it's been having some problems running when the engine is cold. When it warms up, it runs fine. When I'm stopped in the traffic with the engine still cold, the RPMs would go up and down, which resolves itself upon warming up. Also, when I'm stopped in the traffic and am about to keep driving, the engine would hesitate and for several seconds until it finally gathers power and speeds up. While this is happening, I can floor the gas but the acceleration is really sluggish. After this, the car would shift well and run okay. What might be causing it?

There are numerous potential causes for the problem you are having. One thing that comes to mind is a failed engine coolant temperature sensor (ETC). The ECT does exactly what it sounds like - it monitors engine temperature. The ECT’s input to the powertrain control module (PCM) affects the entire engine management operating strategy. Many of the engine’s fuel, emissions and driveability are directly affected by ECT operation. This can result in driveability issues such as those you are having. The first step in diagnosing your vehicle is to retrieve any stored diagnostic trouble codes (DTCs). These codes serve as a starting point for any further diagnosis. A professional will be able to do this and diagnose your car’s acceleration issue. I suggest you give the team at YourMechanic a call since we come to your home or place of work.

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