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International Automotive Technicians Network
Re: What cause Rich fuel trim at wot?
Posted to Technical Discussion Forum on 1/19/2013

There are no "rules" for that. It depends on the type of fuel control system. Most older systems ran in open loop at heavy load so you'd usually NOT see STFT active under those conditions. New cars do trim under high loads.

A speed-density system will do tha... Login to read more.