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View listing at Midwestmiataparts; opens in a new tabMiata · Buyer's guide
1999-2005 NB Miata Idle-Air-Control Valve and Throttle-Body Diagnosis
1999-2005 North American NB Miata 1.8L. NA idle valves and modified throttle/ECU systems are excluded.
Current seller options
WHERE TO BUY
Open an exact listing, then confirm fitment, stock, price, and shipping with the seller before ordering.
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What you need to know
Check intake/vacuum leaks, throttle cable/plate, coolant flow where applicable, wiring, base-idle procedure and ECU inputs before buying. Modified ECUs/throttles require their own calibration.
OEM numbers
Checked NB idle-air-control valve BP4W-20-660. NA valve B61P-20-660 and automatic-transmission modulator valves are different and excluded.Supersession
No NA-to-NB or throttle-body supersession is asserted. BP4W-20-660 is a component mounted to the NB throttle body, not proof the complete throttle body is defective.
Fitment
Check intake/vacuum leaks, throttle cable/plate, coolant flow where applicable, wiring, base-idle procedure and ECU inputs before buying. Modified ECUs/throttles require their own calibration.
Aftermarket options
New OEM, aftermarket and tested used BP4W-20-660 paths exist. Very low-cost unbranded valves require connector/quality and return review.
Before you buy
NB 1.8 only. Vacuum leaks, coolant flow, throttle adjustment, wiring and ECU inputs can mimic an IAC fault. Do not force an NA valve or modified-throttle solution into this stock-service decision.
Research and fitment sources
Supersede reviewed 7 unique research sources for this guide. 4 also appear above as a seller or official action and are not repeated here; 3 additional citations follow.
Research last verified .