| Mazda Tips | October, 1998 |
| VIN: JM1NB3532X0104150 | Category: F Fuel and Emission | ||
| Repair information: Reference #: 2831 | Type Desc.: Tip | ||
| Model Miata |
Year 1999 |
Affected Vin Range All |
Model Specs All |
Symptoms and conditions
Engine may run rough and stall during warm-up. Once engine reaches operating temperature, problem will go away. When engine stalls, it will immediately restart. No fault codes present.
Incorrect exhaust cam (HLA style) may have been installed during production. Profile of HLA cam does not allow exhaust valves to seat properly during engine warm-up causing a loss of compression.
Expansion differences between the head and valves during warm-up is the reason why this condition only occurs at specific coolant temperatures of between 100-140 degrees fahrenheit.
Repair Procedure
Check for proper clearance at the exhaust cam by referring to WSM procedures and specifications. If they are found to be far less than specifications, replace the cam with P/N BP4W-12-440 and adjust the valve clearance as necessary.