My brothers 99 FED version is getting this code... Any Ideas what I should do?
His car has is all stock and has 32k miles on it.
Thankyou to all hte guru's out there!

 

All OBD-2 engines have four-digit Diagnostic Trouble Codes. Your "code 66" is probably DTC 0606, a misfire on cylinder #3.

A variety of problems could spawn this code...
- Improper spark plug
- Insufficient compression
- Incorrect fuel pressure
- Exhaust Gas Recirculation volume control valve
- Open or shorted fuel injector circuit
- Faulty fuel injector
- Air leaks in the intake manifold
- Open or shorted secondary ignition circuit
- Lack of fuel
- Magnetized signal plate (flywheel or A/T drive plate)
- Front oxygen sensors

The rear bank of cylinders is #1, #3, #6 (passenger side to driver side). If you care to do some diagnosis on your own, consider the following steps.

1) Exchange the #1 and #3 ignition coils.
2) Exchange the #3 and #5 spark plugs.
3) Reset the ECM.
4) Drive the car normally and wait for the Service Engine Soon light to go on.
5) Do a DTC readout.

If the misfire DTC points to #1, you probably have a bad coil assembly.
If the DTC points to #5, you probably have a bad plug.
If the DTC still points at #3 you have at least narrowed the scope of investigation and should proceed to ...
- do a fuel pressure test
- do a compression test
- do the sound and resistance tests on the fuel injectors