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Q: Engine shakes at idle, burning smell, only in cold temperatures

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Most of my issues ONLY happen when it is cold outside. When idling, either in park or at a stop light, my car does the following: - Idles EXTREMELY rough. Makes knocking noise. - Low RPMs, sometimes RPMs bounce up and down. Feels like it is going to stall, but doesn't. - Burning smell coming from vents (only happens after about 10 minutes of driving). - When it's extremely cold outside, my check engine light will blink when idling rough and then stop once I accelerate.

Other symptoms that I've noticed year round, regardless of temperature: - Car vibrates when using power windows, using heat or AC, and turning lights on.

  • Jerks a little when changing gears

Today I had a full tune up, new PCV valve, new valve cover gasket, and new air filter. No improvements, but CEL is now off. Mechanic said I'll need new motor mounts (for vibration), but shaking at idle, burning smell, and jerkiness all remain. Any suggestions?

My car has 165000 miles.
My car has an automatic transmission.

Hi there. The vibration could be the engine mounts loose on your engine or transmission. The engine knocking noise could be the engine pinging as there is not enough fuel to burn and the cylinders are colder than normal. This is a normal condition, however, if the condition continues as the engine is warm, then the engine temperature sensor has failed. The smell of burning in the vents is the dust burning off the heater core as the heater is operated. This is similar to the heater in a house that burns off the dust on the heating element causing the burning smell. The cabin air filter could also be full of dust causing the burning smell too. If you need further assistance with the vibrations and smells, then seek out a professional, such as one from Your Mechanic, to help you.

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