Rough idle when fully warm
Engine idles fine cold but gets rough, hunts, or shakes once warm.
When warm, the air-flow sensor plate, idle-air control, and oxygen sensor (if fitted) take over fueling. The idle speed is mechanically set; closed-loop trims via the EHA.
What the diagnosis checks
- Does idle speed hunt up and down (600 ↔ 1000 RPM)?
- Does unplugging the idle-air-control valve change the hunting?
Possible causes it points to
- Idle-air-control valve dirty or failing
- Oxygen sensor lazy or contaminated
- Heat-soak vacuum leak
Parts for this job
KE-Jetronic fuel system sparesBackground reading
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