Miata Technical Service Bulletin

Category Applicable Model(s) Subject
Bulletin No. 001/90
Issued 6/8/90
G 1986 -'90 RX-7 & MX-5 Miata Timing Light Malfunction


A Distributor-Less Ignition system (DLI) has been adopted in the RX-7 and MX-5 Miata since 1986 production. On a DLI system, discharge from the ignition coil is bipolar - one side is negative, the other positive. Therefore, if a timing light is designed to meet discharge from the negative terminal only, it will not light or will light intermittently at the positive terminal.

This condition is not a result of a vehicle malfunction, it is a problem with the design of the timing light. Please pay close attention to this situation to avoid misdiagnosis.

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