Why Is My Car Shaking After Changing Spark Plugs, And How Can It Be Fixed?

Replacing the old and used spark plugs improves the spark efficiency. However, this is only sometimes the case, as you may notice your car shaking after changing the spark plugs.

So, why is your car shaking after changing spark plugs? That is because you have 

• An inappropriate spark plug,
• Damaged spark wires,
• Incorrect spark gaps and 
• Improper plug boot seating. 

Other causes may be due to mixed plug wiring and reverse wiring. Check the manufacturer’s manual for appropriate plugs installation.

This article reviews the causes of your car shaking after changing spark plugs and how it can be fixed. In addition, it also gives information on how to install the plugs correctly.

Car Shaking After Changing Spark Plugs, And How Can It Be Fixed? (Quick Summary)

Below is a quick summary of why your car shakes after changing spark plugs and how to fix them.

Causes	Solution
Use of wrong spark plugs	Get the original spark plug recommended by the manufacturer
Damaged spark plugs wires	Check any damaged wire and repair or replace accordingly
Incorrect spark plug gap	Get the correct gapping measurements for your engine
Mixed up spark plugs wires	Consult the manual guide for correct installation
Inappropriate screw torque	Reinstall the screws with the right torque
Reversely connected spark plug wires	Follow the given guidelines for correct installation

What Causes A Car Shake After The Spark Plugs Are Changed, And How Can It Be Fixed?

Let’s now look at the causes of car shaking after changing spark plugs in detail.

1. Wrong Spark Plug Gapping

Spark plugs operate with an electrode gapping between the earthing and the power electrode. Wrong gapping means the spark will either be delayed or missed if the gapping is too much.

On the other hand, the spark may be passed to the ground wire due to the proximity between the two electrodes. It would be best to have the exact gapping for your specific engine. Most vehicles operate with a spark plug gap of between 0.028“ and 0.032”.

Solution

Since different engines require different gapping, consult with the manufacturer’s guide for an exact gapping measurement for your engine. Use a feeler gauge to measure the gap for accuracy before installing the spark plug.

2. Use Of Wrong Spark Plugs

You may have the right gapping on the spark plug, but still, your car shakes. Most likely, the spark plug you installed is wrong.

The size may be okay and fit perfectly, but it must still be the right type. Such spark plugs cause delayed sparking and even misfiring in extreme conditions.

Solution

Use the original spark plugs recommended by the manufacturer. Avoid spark plugs titled as universal for any engine; get the exact OEM spare for your engine.

You can check the make and type of spark plug you removed for comparison.

3. Damaged Or Mixed-Up Spark Plugs Wires

Several wires are used in the installation of the spark plug. A wrong wiring connection between the spark plug and the ignition coil affects the regular firing order and the proper combustion of fuel. These problems cause your car to shake because the engine has an insufficient power supply.

Solution

Get all the damaged wires replaced, as repairing them may cause similar problems in the future. Check the connection and install the wires in the correct order.

Consult the manual guide for the exact connection sequence.

4. Inappropriate Screw Torque

Spark plugs are held in place by the plug screws. A wrong torquing may exert an excess force that affects the spark plug efficiency. Thus, inappropriate screw torque may affect the plugs causing your car to shake while driving.

Solution

Reinstall the screws with the proper torque. Check the manufacturer’s manual for the exact torque requirements.

5. Reversely Connected Spark Plug Wires

Connecting the spark plug wires in reverse causes misfiring in the combustion cylinders. Reverse wiring causes a change in the firing order of your engine, thus shaking the car while driving.

Solution

Ensure correct connections with the proper sequence to avoid altering the engine’s firing order.

Safety Precautions To Do After Changing The Spark Plug

Once you successfully change the spark plugs, check to ascertain the right connections before getting back on the road.

• Inspect the spark plug wires and the connection to the ignition coil with the manual guide
• Follow the wiring connection from one end to the other
• Repair or replace the damaged cables to avoid short circuits
• If, on removal, you had pulled on the lead and not the insulator cap, check the plug wires for loose connection
• For modern vehicles with coil packs on top of the spark plugs, check if there is an excellent positive connection with every spark plug

If your car is shaking after changing spark plugs, you might find our articles on car shakes when releasing clutch in first gear and car shaking after battery change helpful. Our article on car shakes when releasing clutch in first gear discusses how clutch problems, transmission issues, or engine mounts can cause shaking while shifting gears. Meanwhile, our article on car shaking after battery change explores some of the most common reasons why this issue can occur, such as electronic control unit (ECU) problems, battery terminal issues, or alternator failure. Be sure to check out our resources on car shakes when releasing clutch in first gear and car shaking after battery change for more information.

FAQs

Below are some questions asked by car owners with problems after changing spark plugs-

Conclusion

Changing the spark plugs is a maintenance practice to improve the engine’s performance. However, a slight mistake from the replacement plug type to the installation can cause problems with your engine, such as the car shaking while driving.

Poor installation causes misfiring and altered firing order, which on operation, shakes the vehicle. Ensure proper spark plug replacement by following the manufacturer’s guidelines or consulting a mechanic.