My 99 cougar manual 2.5l has power loss..showin code p1151..weird everymornin when i leave for work it runs AWESOME ..its fast.. responsive etc..however after work it the polar opposite..loss of power has a slight miss around high 3rd every now and again when im stompin on it (cause its just not responding like it should...anyone experience anything similar..and fix? Plz help love this car(whens shes performing)

SOURCE: Turbo problems on 99 Ford F550 7.3 PowerStroke

check for vacuum hoses.

SOURCE: 99 Expedition - Stutters and loses power when accelerating

My was doing the same thing, it was an EGR valve and a misfire on the #2 cylinder which required a new spark plug and a coil pack
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SOURCE: transmission problem with 2nd gear (loss of power, skips)

Go to this link.

SOURCE: engine light on code p1151 on 99 mercury cougar v6 2.5l engine

P1151 (Natural Gas), Lack of HO2S-21 Switch, Sensor Indicates Lean. P1151, Lack of HO2S-21 Switch, Sensor Indicates Lean.
one of your oxygen sensors are bad, or has a bad connection.

SOURCE: 99 silverado sputtering & loss of power(low rpms)

Have you performed a tune up? If not, it's time for one. spark plugs, wires, distributor cap and rotor.