Some Jaguar XKR owners report experiencing rough idling issues accompanied by trouble codes indicating random multiple misfires, such as P0300, P0302, and P0304, which are linked to specific cylinders like cylinder 2 and cylinder 4. These owners often identify potential causes including vacuum leaks, spark plug problems, or ignition coil failures. Additionally, some report symptoms of fuel starvation, prompting checks of fuel pressures for accurate diagnosis. Issues with the supercharger bypass valve have also been noted as a contributing factor to rough idling. Furthermore, maintaining the correct air-to-fuel ratio is crucial, as any discrepancies can exacerbate misfires and idling issues. To resolve these problems, owners may need to reset fault codes, check fuel pressure, inspect the supercharger bypass valve, and ensure optimal air-to-fuel ratios.

Some Mazda Navajo owners report experiencing stalling and rough idle issues, particularly when coming to a stop. Common problems include fuel system malfunctions, such as clogged fuel filters, dirty fuel injectors, or malfunctioning fuel pumps, which can restrict fuel flow to the engine. Additionally, owners have noted that cracks or holes in the air duct can allow unmetered air to enter the engine, disrupting the air/fuel mixture and leading to rough idle and hesitation. Vacuum leaks have also been reported to cause difficulties in maintaining idle, contributing to stalling and rough running. Moreover, some owners experience issues with the idle air bypass valve, which can lead to difficulty starting the engine when cold and stalling at idle. Faulty O2 sensors have been cited as another factor, with symptoms including rough idling, poor fuel economy, and a check engine light. Addressing these issues through proper maintenance and timely repairs is crucial for improving the performance of the Mazda Navajo and resolving these concerns.