An ignition coil may fail causing one of the cylinders to misfire. Each of the two banks of cylinders has its own coil assembly. If one ignition coil fails the coil assembly for the corresponding cylinder bank must be replaced.
Problems for specific Pontiac Bonneville years:
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Newest reported Pontiac Bonneville problems
The outer tie rod ends on the steering linkage may wear causing excessive free play in the steering and uneven tire wear. If the worn tie rod ends are replaced, the wheel alignment should be checked and adjusted as necessary.
The cam sensor interrupter (magnet) may become demagnetized and/or fall off of the camshaft gear causing the Check Engine Light (Service Engine Soon) light to illuminate. On higher mileage vehicles it would be advisable to replace the timing chain and gears if this problem were to occur as the timing cover must be removed to replace the interrupter.
An intake manifold vacuum leak can develop from a variety of sources, often causing illumination of the Check Engine Light with codes P0171 & P0174 stored. Thorough diagnoses will be necessary to pinpoint the cause in order to make the correct repairs. A "smoke" machine is often used to isolate the cause of difficult to find vacuum leaks.
The mode and temperature door actuators may fail causing improper air flow or temperature output from the heating and AC (HVAC) system.
One or more heater & AC (HVAC) air delivery and/or temperature mode door actuator may fail. This can result in incorrect air delivery or temperature. If this occurs, fault code(s) stored in the HVAC control module should be available to assist with diagnoses.