Car runs rough with AC on

ANSWER : Your question makes me think of a case I ran into a few years ago. The owner had modified his car but when he installed his fans, one of them was wired backwards so the fan ran in reverse. The two fans were fighting each other which was just like having no fan at all, so the car heated up while it was sitting still then it cooled off when moving. Check the rotation of both the fans before you check anything else. If that’s OK, you may be able to track down the problem with a non-contact thermometer, follow the course of the coolant with the beam. The radiator should be about 30 degrees or more cooler at the exit than at the entrance. If you need help with this, contact Your Mechanic. They can send a technician to your home to check out your overheating problem and let you know what can be done for it.

ANSWER : Hello, thank you for writing in. Although the pulley is still spinning, the compressor has likely failed. If it is not properly regulating pressure in the system, one of the first signs is a warm air conditioner. Considering yours is not cooling off, the pressures are not correct. If you believe the compressor is working correctly, you may want to check for a clogged line before replacing it. Keep in mind, a blocked line has likely put extra strain on the compressor, and may cause premature failure. For more help with testing or replacing the compressor, contact our service department to schedule an appointment.

ANSWER : The control circuit for the fans needs to be checked. For example, there is usually a condenser fan relay in the A/C electrical controls. There could be a fault with that relay and/or wiring problems, perhaps even just a loose connection, blown or loose fuse, and so forth. To resolve something like this, the recommended service is an electrical component diagnostic. If you request that diagnostic service, the responding certified mechanic will get the problem pinpointed and resolved. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.

ANSWER : This may be a sign of a faulty MAP sensor as the vehicle responds adversely to a load put on the motor (i.e. putting it in gear, turning on AC or engaging the brakes). The Manifold Absolute Pressure (MAP) sensor senses engine load and generates a signal that is proportional to the amount of vacuum in the intake manifold. The engine computer then uses this information to adjust ignition timing and fuel enrichment. When the engine is working hard, intake vacuum drops as the throttle opens wide. The engine takes in more air, which requires more fuel to keep the air/fuel ratio in balance. When the computer reads a heavy load signal from the MAP sensor, it adjusts the fuel mixture to slightly more rich than normal so the engine can produce more power. The computer will then retard (back off) ignition timing slightly to prevent detonation that can damage the engine and decrease performance. This may also be caused by other closely related components such as a dirty or failing mass air-flow sensor, a faulty throttle position sensor or potentially a vacuum leak. I would recommend having an expert from YourMechanic come to your location to diagnose and inspect your vehicle.

ANSWER : There are reports that the replacement alternators will not communicate with the engine computer and will not charge correctly. I recommend using only the manufacturer approved replacement part. It can be new or remanufactured but approved for use in the vehicle. Some lower cost alternators on the aftermarket will have charging problems since they will not communicate with the ECM on the vehicle and will stop charging.

ANSWER : Hello and thank you for your questions. If your engine was rebuilt about 10 months ago, the question is to determine if the management system has been installed as well. With the symptoms that you are having, it sounds like the coil packs are old and in need of replace. You replaced numbers 1 and 4 and now number 6 is not firing. I recommend replacing number 6, 2, 3, and 5. This will ensure that you have all 6 coil packs that are new.

Just because the coil packs are okay during a test doesn’t mean that they are functioning correctly. Coil packs on Buick vehicles from 1998 – 2005 last between 150,000 to 200,000 miles. I also recommend having your fuel injection system flushed. Unless you have new injectors, the old injectors could cause a cylinder to fail, even though it is working correctly. These symptoms can cause the engine to have a rough idle and rough running during conditions. If you need assistance troubleshooting the rough running condition, I recommend having a professional, like one from YourMechanic, inspect the car and move forward with repairs.

ANSWER : I have only seen this situation once in my 30+ years and it turned out to be a broken crankshaft pulley. Belts are driven by the engine. The crankshaft pulley spins the belts, which in turn spin the air conditioner compressor, power steering and water pumps, and the alternator. The vehicle should be towed to your local repair shop and not driven. Without the water pump spinning to circulate the coolant, the engine will quickly overheat and result in more extensive damage.

ANSWER : This is normal when the AC is on. The air conditioning compressor requires torque from the belt system on the engine to power it. When the AC is off, the compressor clutch does not activate, meaning the AC is not straining the engine. When the AC is on, the compressor clutch activates, causing the drive belt on the engine to turn the compressor. The Idle Control Actuator is what controls the engine idle. When the AC kicks in, the engine will drop some RPM, and the actuator opens to allow more air into the engine. When you are at speed, the throttle is open from the accelerator pedal under your foot. the Idle control actuator is not active at this time.
What you describe is normal.