Check Engine Light After Spark Plug Change: Common Mistakes
Key Takeaway
Changed spark plugs and now the CEL is on? Here are common installation mistakes.
Common Spark Plug Mistakes
| Mistake | Resulting Code | Fix |
|---|---|---|
| Wrong plug gap | P0300–P0308 | Re-gap to spec |
| Coil connector not seated | P0351–P0358 | Push until it clicks |
| Wrong plug type | P0300, rough idle | Install correct plugs |
| Cross-threaded plug | P030X | Remove, repair threads |
| Plug not torqued | Misfire or compression leak | Torque to spec |
| Vacuum hose knocked loose | P0171 | Reconnect hoses |
How to Fix
1. Scan to identify which cylinder is misfiring.
2. Re-check that cylinder's plug — gap, torque, connector.
3. Clear code and test drive.
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