Hi,
One quick question so that I may help you out better- when you say you are slowly losing coolant, is there an external leak that you see coolant on the ground?
Ok- everything is probably related. I am going to give you the possiblities of each trouble code and how its all tied in:
DTC P0136-
DTC P0174-
DTCs P304 and P305-
The most likely reason for the problems are internal engine wear, in a manner of speaking. Look at diagram below and you will see that cylinders #4 & 5 are next to each other.
One form of internal engine wear is low engine compression. This can happen because of several reasons. Two reasons that can cause this and cause the misfire codes and the coolant loss, as well as the lean code is a leak at the head gasket between cylinders #4 & 5, or more likely, a leak between those two cylinders on the intake manifold gasket or intake manifold itself.
And if coolant is getting into the cylinders, the plugs will foul out, and the coolant goes thru exhaust system and contaminates the O2 sensor. Also, because there is loss of engine compression, it will cause the engine to run lean.
To confirm this, a coolant pressure lekdown test needs to be done. This will identify the internal coolant leak. At that point, the internal leak will need to be repaired, and replace the fouled out plugs and contaminated O2 sensor as well.
Windstars have problems with intake manifold and manifold gasket leaks, and I strongly suspect that as the cause of all your vehicle's problems right now. Having this repaired at a shop, including plugs and O2 sensor, you can expect to pay between $675-800 parts and labor.
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This is a Paysite
Automotive Repair Shop Manager
Automotive Repair Shop Manager, Technician/JA Mentor
Here are some prices(may vary some depending on what shops charge per hour for labor in your area)
Testing - $60
Intake manifold gasket, including O2 sensor and plugs - $650-800 parts and labor
Intake manifold, including O2 sensor and plugs - $800-1000 parts and labor
Head gasket, including O2 sensor and plugs - $1500 and up parts and labor(would depend on whether heads had to be machined or even replaced- could add another $500 or so to bill)
Of the above the most likely is either intake manifold gasket or intake manifold. As I said, both are very common failures. I also lean towards the these because of slowness of internal coolant leak. Usually a head gasket will be a more severe leak and very noticable white smoke from exhaust as well as the oil looking muddy in color due to lots of coolant in oil.
Good luck, and let me know if you need any more help