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The duct carrying warm air from the exhaust manifold shroud to the air cleaner, missing or perished. It is usually a flexible foil or paper hose that embrittles with heat and is frequently thrown away rather than replaced.

Without it the intake can only draw cold air, so the temperature control system has nothing to select and the module reports that intake temperature is not responding as commanded. The practical symptom is poor cold-weather driveability — hesitation and stumbling until the engine is thoroughly warm — which is easy to attribute to fuelling. Check the duct exists and is connected at both ends; it is often found lying in the engine bay or absent altogether after earlier work, and the manifold shroud it connects to may also have corroded away.