2002 Navigator: heater issue and P0430 issue
I have done some searching and I think I have the heat issue narrowed down. I just want to double check with people here with a little background on the car.
The car has 150,000 miles on it. We got it with 32k. The coolant has not been changed since we've owned it. I just checked and it looks pretty cruddy, but it is at the proper level.
The heater does not blow hot. I can turn the HVAC system off for awhile and turn it back on and it will blow hot for about 15 seconds. This makes me think that the front heater core is plugged up. The back air acts the same way, so I think that heater core is plugged up too. Is it likely that they are both plugged up given the condition of the coolant? The temp. gauge comes up to about halfway, so I think the thermostat is still good. I feel like I'm due for a cooling system flush and try to unclog the heater cores. What is the best way to go about this? Should I change the t-stat at the same time?
Next, it is throwing a P0430 code. Again, the car has 150k miles and has not had the O2 sensors changed. It still averages 15.8mpg. Is it likely that I just need to replace all 4 O2 sensors and that will solve the problem? About 15k miles ago a few of the coil packs went out and we only changed the bad ones and their plugs. The car does not feel like it is running rough at all. Every now and then if you are accelerating from a stop the engine will hesitate, but that doesn't happen very often. There is a big rattle from the driver's side of the car sometimes when the car is in gear and at idle. I haven't had a chance to get under there and figure out what that is yet.
Also, the car ran regular unleaded gas for about 30k miles. If that affects anything.
Sorry to ramble, I'm just trying to think of anything that would help in the diagnosis.