Has the 2012 Focus Shaking Issue Been Perfectly Resolved?

[EmmettRose]

2012 Focus shaking issue has not been resolved yet. The reasons for the shaking are as follows: Severe engine carbon buildup: The most common cause of car shaking is excessive dirt on the throttle body or carbon buildup in the fuel injectors. When there is too much carbon buildup inside the engine, the gasoline sprayed by the cold start injector will be largely absorbed by the carbon deposits, resulting in an overly lean air-fuel mixture during cold starts, making it difficult to start. In this situation, the car will only start easily once the carbon deposits have absorbed enough gasoline. After starting, the gasoline adsorbed on the carbon deposits will be sucked into the cylinder by the engine's vacuum for combustion, making the air-fuel mixture too rich. The engine's combustible mixture alternates between being too lean and too rich, causing idle shaking after a cold start. The lower the temperature, the more fuel is needed for a cold start, and the presence of carbon deposits will significantly affect whether the cold start proceeds smoothly. Solution: Clean the fuel system and check if the idle air control valve has carbon buildup, which should be cleaned if necessary. Ignition system issues: Check the condition of the spark plugs, high-voltage wires, and ignition coils. Poor performance of the ignition system or weak sparking from the spark plugs can also cause such issues. Solution: Check if the spark plugs have excessive carbon buildup and replace them if necessary. Unstable fuel pressure: If you have already cleaned the engine carbon deposits, throttle body, replaced gaskets, and spark plugs, but still notice shaking at idle, it is recommended to visit a 4S shop to check the fuel supply pressure and the intake pressure sensor. Abnormal fuel pump supply pressure or incorrect readings and poor performance of the intake pressure sensor can cause the car to shake. Solution: Check the fuel pressure and replace components if necessary. Aging engine components: Car shaking can also be related to the aging of engine mounts (also known as engine supports). Engine mounts are essentially the engine's shock absorption system, responsible for absorbing minor vibrations during engine operation. If the engine mounts are faulty, these vibrations will be transmitted to the steering wheel and the cabin, causing shaking at idle. Solution: Replace the components.

[Tiffany]

Former owners of the 2012 Focus, let's talk about the shaking issue. I drive the same model and had the same problem a few years ago—idling so rough it felt like dancing. Tried all sorts of fixes: cleaning the throttle body is basic, plenty of online tutorials, just buy a can of cleaner and spray it; replaced the spark plugs with OEM parts, which helped a bit but didn’t completely solve it; the most effective fix was replacing the engine mounts—the rubber deteriorates and amplifies vibrations. After all that, it’s finally bearable. A perfect fix? Doubt it, since wear and tear is normal for older cars. Regular maintenance is key to keeping it under control. My advice: don’t just swap parts, pay attention to driving habits—ease on the throttle, and use good fuel additives to clean carbon buildup. If the shaking gets severe, head straight to a 4S shop for a full diagnosis—don’t gamble with safety. Repairs cost me a few hundred to over a thousand, but it’s worth it.

[DeKaleb]

As someone who frequently repairs Ford vehicles, shaking in this generation of Focus is all too common. Most cases stem from carbon buildup blocking the throttle body—disassembling and cleaning it can provide relief. Worn-out spark plugs causing unstable ignition or faulty ignition coils can also be culprits. The worst scenario is aging engine mounts, which transmit vibrations directly into the cabin. A perfect fix? Unrealistic, but improvements are possible—comprehensive servicing including carbon cleaning, replacing spark plugs and coils, and checking mount elasticity. Post-repair, 90% of cars run smoothly, taking about two hours and costing a few hundred dollars at minimum. Regular maintenance is key to preventing shakes: inspect the throttle annually to avoid blockages. If shaking comes with unusual noises, check the engine bearings—avoid cheap aftermarket parts that compromise longevity.

[CameronFitz]

Having been active in the Focus forum for several years, discussions about the 2012 model's shaking issues are as common as daily meals. Popular DIY solutions include cleaning the throttle body, which is simple and effective; replacing spark plugs for immediate improvement; and in severe cases, changing the engine mounts usually does the trick. The perfect solution varies by individual—some never experience recurrence after cleaning, while others find their mounts irreparable, and upgrading the ECU software can adjust idle speed. Overall, it's manageable, with the core being timely maintenance to prevent carbon buildup. If costs are low, DIY is an option; if high, visit a professional shop—don't expect a permanent fix as part aging is inevitable. Checking fault codes avoids detours, and experience shows that diligent maintenance leads to fewer shaking issues.