Carbon on the intake valves
Attaches to 4GR-FSE at engine level · Turbo & intake · carried by 1 variants across 1 chassis
Overview
Carbon on the intake valves is a occasional fault recorded against 4GR-FSE at engine level, typically from 150–250k km. It shows up as a slightly rough idle, a cold misfire, and a gradual loss of response over a long period. Where it's documented, the repair runs €350–€600 (walnut blasting with the intake manifold off, costs dated 2026-07), and it can be partly checked before you buy. 1 variants across 1 chassis in this database inherit it.
What happens
Symptom. A slightly rough idle, a cold misfire, and a gradual loss of response over a long period.
Cause. Direct injection means no fuel washes the back of the intake valves, so oil vapour deposits build up. The additional port injectors keep this far milder than on the German direct-injection engines, and it takes high mileage to matter.
How to check it
Static checks
Borescope the intake valves, or simply ask whether the car has ever been decarbonised at high mileage.
Engine off, ideally on a lift.
Every variant that carries this
| Variant | Chassis | Body | Years | Risk | Good buy | Cost as % of good buy |
|---|---|---|---|---|---|---|
| IS 250 4GR-FSE | XE20 | sedan | 2005–2013 | R1 | €5,750 | 8% |
The last column is the point. The same repair is an inconvenience on one variant and a reason to scrap the car on another. A failure costing a quarter of the vehicle's value changes the purchase decision regardless of how rare it is.