Jeep overheated while sitting still/driving slow. low engine coolant light keeps coming on, but radiator is full and so is overflow tank. sitting at stop lights the rpm's drop down to 400. check engine light is on and produces code: p 0303 (misfire in cylinder #3) dont't know if they are all related. hoping it is just the thermostat....took to mechanic and he said that it was the fan but that i needed to take it somewhere else who could diagnose it because he didn't have the proper equipment. thought i heard the fan come on when jeep overheated so this doesn't make much since to me. (it was very loud)

SOURCE: My 99 Jeep cherokee laredo keeps overheating

Overheating with knocking and shaking is a very good chance that you have water/Anti freeze in your oil and that would be a blown heat gasket or cracked head or water jacket.(check oil filler cap and dip stick for creamish white reside . That will also explain the constant over heating. In my opinion you need at least a head job or may need to rebuild or replace motor. Good Luck

SOURCE: Check Engine light flashes and car vibrates

The only scenario I am familiar with that causes a blinking or flashing Check Engine Light is misfires. Your description of the car shaking is another sign of possible misfires as well. There could be other issues, it would be helpful to know what codes are getting set. However, with the flashing check engine light and the shaking of the car the first thing I would do, if it hasnt been done in a while, is a tune up. Replace the plugs to start. I believe you have a distributorless ignition meaning that you have coil packs instead of a distributor.

Your coil pack sits on top of the plugs. Look to the left side of the engine, just at the bottom of the valve cover and you will see (assuming you have the 4.0L 6-cylinder engine) a series of three humps. Those three humps is your coil packs and there should be four bolts that hold it in. Take out those four bolts, pry up the coil pack and then you will have access to replace the spark plugs.

While your at it, Id replace the fuel filter, air filter and other general maintenance/tune up items like that.

SOURCE: check engine code P0740 (torque conv clutch no rpm

Low fluid pressure to the torque converter Have seen this before. I first try to flush the fluid and replace the filter fixed the problem most of the time. If that doesn't work u need a new torque converter.

SOURCE: MISFIRE CYLINDER #3 CHECK ENGINE LIGHT COMES ON VEHICLE

Check spark plug wires for corrosion

Thomas Perkins

• 15088 Answers
• Posted on Apr 10, 2011

SOURCE: I have a 2000 Jeep Grand Cherokee, 4.7litre V8.

Trouble Code: P0320

No Crank Reference Signal to PCM
Possible Causes:


CKP Sensor signal circuit is open or grounded. CKP Sensor VREF circuit is open or grounded. Tone wheel or flex plate damage or erratic CKP Sensor signals. CKP Sensor is damaged or has failed. PCM has failed. 4.7L
The Crankshaft Position Sensor (CKP) is mounted into the engine block above the starter motor. Engine speed and crankshaft position are provided through the crankshaft position sensor. The sensor generates pulses that are the input sent to the powertrain control module (PCM). The PCM interprets the sensor input to determine the crankshaft position. The PCM then uses this position, along with other inputs, to determine injector sequence and ignition timing. The sensor is a Hall effect device combined with an internal magnet. It is also sensitive to steel within a certain distance from it.
On the 4.7L V8 engine, a tone wheel is bolted to the engine crankshaft. This tone wheel has sets of notches at its outer edge. The notches cause a pulse to be generated when they pass under the sensor. The pulses are the input to the PCM.

4.7L

The Crankshaft Position (CKP) sensor is bolted to the side of the engine cylinder block above the starter motor. It is positioned into a machined hole at the side of the engine block.

1. Remove starter motor.
2. Disconnect CKP electrical connector at sensor.
3. Remove CKP mounting bolt.
4. Carefully twist sensor from cylinder block.
5. Remove sensor from vehicle.
6. Check condition of sensor O-ring.
   
   
4.7L
The Crankshaft Position (CKP) sensor is bolted to the side of the engine cylinder block above the starter motor. It is positioned into a machined hole at the side of the engine block.

1. Remove starter motor.
2. Disconnect CKP electrical connector at sensor.
3. Remove CKP mounting bolt.
4. Carefully twist sensor from cylinder block.
5. Remove sensor from vehicle.
6. Check condition of sensor O-ring.
   
   
Duralast/Crank position sensor.part#SU3181 for 25.99 at AutoZone.