Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Idle Air Control Valve: Miata
- Resistance Inspection
Disconnect IAC valve 2-pin harness connector. See IAC VALVE LOCATION table. Using an ohmmeter, measure resistance between IAC valve terminals. See IAC VALVE RESISTANCE SPECIFICATIONS table. If IAC valve is okay, check for open or short circuit. Go to next step. If resistance reading is not within specification, replace IAC valve. - Open Circuit Inspection
Disconnect PCM 17-pin harness connector. Check for continuity between following terminals:- Power circuit - IAC valve harness connector terminal "A" and PCM 17-pin harness connector terminal No. 2P (Orange wire).
- GND circuit - IAC valve harness connector terminal "B" and PCM 17-pin harness connector terminal No. 2Q (Violet/Red wire).
If continuity is present, go to next step. If continuity is not present, repair open circuit in suspect wire or replace wire harness. See appropriate WIRING DIAGRAM under ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS.
- Short Circuit Inspection
Check for continuity in Orange wire between IAC valve harness connector terminal "A" and PCM 17-pin harness connector terminal No. 2P to ground. If continuity is present, repair short circuit in Orange wire between PCM 17-pin harness connector No. 2P and IAC valve harness connector terminal "A".
| Application | Location |
|---|---|
| Miata | On Bottom Of Throttle Body |
| MPV, Protege & Protege5 | On Top Of Throttle Body |
| Application | Ohms | ||||
|---|---|---|---|---|---|
| Miata & MPV | (1) 8.7-10.5 | ||||
| Protege & Protege5 | (2) 7.7-9.3 | ||||
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
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