Misfires under load (acceleration) can be caused by spark plug wires arcing to the cylinder head in the spark plug wells. Water in the spark plug wells can also cause the same problem so careful diagnosis is needed.
Problems for specific Mazda Miata MX-5 years:
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Newest reported 1990 Mazda Miata MX-5 problems
If the engine runs poorly, has a misfire, and/or loss of compression after camshaft installation, it may be caused by the hydraulic valve lifters over extending while the cam was out. If the lifters are extended, they will hold the valves open and cause a loss of compression. Our technicians recommend running the engine for 15 minutes, or let it sit overnight to allow the lifters to readjust to the proper position.
The engine may idle roughly or stall when it's cold because the oil pump pressure relief plunger is sticking. Failure is usually due to wear and it causes excessive oil pressure to pump up the hydraulic valve lifters keeping the valves from closing completely, which results in a loss of compression. The oil pump will need to be replaced in this case.
A loud ticking noise (hydraulic valve lifter noise) may be heard from the top of the engine, particularly when the engine is still cold. The noise may occur more frequently on higher mileage vehicles; Hydraulic valve lash adjusters may need to be replaced to correct this issue. Following the maintenance schedule for oil changes will also help prevent a recurrence of the noise.