Car Shakes When Accelerating

What it feels like

• The whole car rocks or stutters as you press the pedal, then smooths out when you lift
• A jerking feeling at a steady highway speed, as if the engine cuts for a split second
• The check engine light blinks on and off while it happens
• Loss of power on a hill that was not there last month

Codes that usually produce this

• P0300 Random or Multiple Cylinder Misfire Detected Stop driving 2 weeks estimate
• P0301 Cylinder 1 Misfire Detected Stop driving 2 weeks estimate
• P0171 System Too Lean (Bank 1) Drive with caution 2 months estimate
• P0335 Crankshaft Position Sensor A Circuit Stop driving 2 weeks estimate

Check these first, in this order

Free checks first. Nothing here costs money except the fuel you burn.

1. 1

   Read the stored and pending codes with any scanner, and write down every misfire counter you can see. Pending codes matter as much as stored ones.

   What you'll seeA cylinder number that counts up while the others hold at zero.

2. 2

   Open the hood and look along the top of the engine at the coil packs. Check for a burnt smell, a cracked body, or oil pooled in a plug well.

   What you'll seeCoils that all look alike. One darker than its neighbors is your suspect.

3. 3

   Pull one spark plug and hold it next to a neighbor. Compare the tip color and the gap.

   What you'll seeA light tan tip on both. A black wet tip or a worn electrode points at that cylinder.