yup it sounds like a vac line problem. i forgot to hook that block of vac lines back up after changing the heater core and the same thing happened
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89 GT AOD w/ shift kit, B&M rachet shifter, Trickflow intake, Crane (E-type) cam, 70Tb, 75MAF, 1.6 Rockers, Pulleys, MAC headers and H-pipe, Dynomax mufflers, K&N, 3 core radiator, white face gauges, custom interior, cobra R rims
89LX 2.3 Notch, daily beater!
MY89GT