Check Engine Light With Rough Idle: Quick Checklist
Key Takeaway
Rough idle plus check engine light? Run through this checklist.
Quick Diagnosis Checklist
| Check | What to Look For | Likely Code |
|---|---|---|
| Spark plugs | Worn, fouled, wrong gap | P0300–P0308 |
| Ignition coils | Cracked or corroded | P0351–P0358 |
| Vacuum hoses | Cracked, disconnected, hissing | P0171, P0174 |
| MAF sensor | Dirty or contaminated | P0101 |
| Idle air control | Stuck or clogged | P0505 |
| Fuel injectors | Clogged or leaking | P0201–P0208 |
| Throttle body | Carbon buildup | P0121 |
Priority Order
1. Scan the code first.
2. Check spark plugs — #1 cause of rough idle + CEL.
3. Inspect vacuum hoses — listen for hissing.
4. Clean the throttle body.
ProHow Steer Helps
Steer reads the code and walks you through the most likely causes in order of probability.
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