2006–2010 Lexus IS: Rough idle or intermittent misfire (IS 250 carbon buildup)

Likely causes, ranked

Carbon on intake valves and portsShop

Real-owner fix counts will appear here as reports come in.

DIY or shop: See DIY or shop section

Parts to check

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Carbon on intake valves and ports on Amazon

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Symptom: Intermittent rough idle or shaking at stops, sometimes P0300–P0306 misfire codes.

Likely causes

Carbon. ClubLexus owners trace this to carbon on the direct-injection engine's intake valves. Lexus covered eligible cars under a program for a limited time, and owners otherwise pay for a cleaning.

DIY or shop?

Shop.

Useful steps

Read misfire codes.
Ask a Lexus dealer if any program still applies.
Consider an intake valve cleaning.

Vehicle focus: 2006–2010 Lexus IS.

Safety / mechanic note

None

Related trouble codes

P0300 Random/Multiple Cylinder Misfire Detected
P0301 Cylinder 1 Misfire Detected
P0302 Cylinder 2 Misfire Detected
P0303 Cylinder 3 Misfire Detected
P0304 Cylinder 4 Misfire Detected
P0305 Cylinder 5 Misfire Detected
P0306 Cylinder 6 Misfire Detected

Recalls & service bulletins

Technical service bulletins

L-TT-0192-15 Lexus procedure for intermittent rough idle or misfire on the IS 250 from carbon deposits. Details

NHTSA complaints: NHTSA complaint search returned too few keyword matches under this model name to be a reliable count.

Always check your VIN for open recalls at nhtsa.gov/recalls.

Sources

What actually fixed it?

Had this problem? Tell other owners what the real fix was. Reports are counted above; we never show made-up numbers.