Don't worry about code 73. Codes 12 and 13 have to due with several sensors. First put everything back together and make sure nothing is loose. Code 33 I'm not sure about, my model does not have a EGR valve that I know of. Remove the negative battery cable and wait 30 seconds, to clear all computer faults. Then reconnect battery cable. Rerun the key-on engine-off self test to verify the error codes. DO NOT run the engine or crank it at this time. Any codes that that show up now will be caused by sensor malfunctions. Ignition module can be simple tested, but if you have not already done so-replace it. Test or replace the coil. In the schmatics, circuits tend to be tied together by splices. Because of that, one problem in a circuit can cause a false problem in another. The next steps to figure this out will take electrical experence and lots of time. After going through checking for error codes and check ALL sensors, even the IAC and ECT. Replace them all if need be. If the problem is still there, we'll have to dig a lot deeper, ready? Disconnect the negitive battery. Disconnect the computer module connector and check all pins on both the connector and the computer module. Clean off any grease found and make sure none of the pins can push out of the connector housing. The computer module has soldered pins. You can apply a light coat of clear electrolic grease on those pins to improve the connections. With the computer disconnected, also disconect the TFI connector. Use a ohm meter to check for open circuits between both connectors and check the SPOUT connector. The pins are #55, 36, 16, 20. If these are all closed circuits, plug the connectors back in and make sure no pins have poped out. I can't go through all the tests here, it took me a whole weekend to run through all the tests, when I found the problem with mine. I had to replace several wires and I got rid of that large cheap connector. If you can get small terminals that can tightly fit around the pins on the EEC-IV module, get some electrical wire and connect the ends between both connectors using those terminals making sure you don't mix up the wires. Even though there are 60 pins to deal with, the computer only uses about half of them. The others are not listed in my book. The wires can help you in trouble-shooting. On the passenger side near the fender under the hood, there should be a large fuse box. Under the fuse box is another box that contains three relays. If you have such a device, you will need access to those relays, some Ranger models do not have a power disribution box. One relay is green, one is gray, one is black. The green one is for fuel, black is power to the EEC-IV, gray is the air condtioner which also goes to the fuel injectors. Check to make sure those relays are working and there is power going through when active. Check the condition of the engine too, make sure your compression is good, oil pressure is good. Also look for any wire bundles going around the exhaust pipes. The PVC electrical wire used is sensitive to heat and can easily melt causing shorts. A TFI problem is mostly due to a short somewhere in the electrical system. Can be anywhere, you will need to remove fuses one at a time and disconnect any systems not related to the TFI system. Take a close look at the wire bundle on the driver side that goes from the fender connectors down the side to the transmission neutral switch, solenoids. If any of those wires have damaged insulation, it could cause lots of engine problems. If these become shorted, the convertor will lock up causing a lack of power and making the engine work a lot harder against the convertor causing the flex plate to break, and blow the head gaskets. That bundle also has live 12v power feeds in it. Your next step will be to get a electrical book that shows the computer TFI wiring. The OEM factory books are the only ones I know of that have all the trouble-shooting proceedures in it. Good Luck.