at idle map reading is 8 but vacuum checked is 25

Question

checked vacuum at idle is 25 in lbs map shows 8 or 9 what should map read at idle?

Answer 1

Sound about right. What the ECM see is voltage from the MAP signal. KOEO (Key On Engine Off) the voltage at the MAP signal should be about 4.1 vdc. At seal level. (3.3 vdc at 4700FT)  Idling the voltage should be about 1.9vdc. Idle after warm up is below 1.0 vdc.A is ECM ground

C is (GRY) Boost air temp signal. D is (RED) ECM 5 volts B is (PUR) Map signal , measure the MAP signal