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WHat is the model and engine size of your Mercury vehicle? Are you looking for the mass air flow sensor? Do you have a check engine light on and a code for it?
Ok that sounds right.
P1151 is for the bank 2 oxygen sensor indicating lean. This is most likely due to a vacuum leak at the ocv tube/elbow on the intake manifold.
If the tube is leaking the parts will run about $40.00 at the dealer. The intake is under the engine cover. Here's a pic of the vacuum connections. Trace them back to pinpoint the leak at the elbow in the back of the engine.
Mercury Technician
12 years at a Ford Lincoln/Mercury and Jaguar dealer as a technician and shop foreman.