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The rear Oxygen Sensor ( the one at the end of the CAT ) does not have anything to do with starting the engine. It is only for checking the efficiency of the Catalytic Converter. ( usually the test is run at highway speeds after the vehicle is warned up ) Are you getting a Check Engine Light that indicates that the rear Oxygen Sensor was setting a fault code? The rear Oxygen Sensor should read at about .700-750 volts much of the time at highway speeds. It is not supposed to go up and down like the front Oxygen Sensor. As far as long cranking, I have replaced a lot of fuel pumps for this reason because the pressure holding check valve wears out and it takes about 7-10 full cranks before system pressure is built up enough to feed the injectors. One way to test this is to see if the car takes longer to crank as it sits for 1/2 hour, then 1 hour, then 1.5 hours etc or have a technician put a fuel pressure gauge and then see if the rest pressure goes way down. It should hold within 10 psi of system pressure for 24 hours. Hope this info is a help, if not, email back and I will respond. The fact that your rear Oxygen sensor is going back and forth does not necessarily mean that it has a problem. Can you recall the specific code? Some Jeeps use a different Oxygen sensor system that uses a 5 volt scale. Was the 4.5 volt reading from a scan tool or a digital volt meter? And, always be sure that the scale is absolutely correct because 4.5 could be .45 which is a very normal reading. If it's going back and forth too much, it can mean that the CAT is getting 'tired'. The rear Oxygen sensor should move VERY slow and NOT mirror the front, or it means that the CAT is weak. This is the purpose of the rear O2, to test the Cerium bed of the CAT ( which stores Oxygen to burn up the pollutants ). The code P0420 is a code for the CAT getting weak though many people Misinterpret it to mean that the rear O2 is bad. Let me know what you find
It sounds like an engine misfire is occuring. Does the car go in to the lower gear and eventually accelerate? It sounds like your vehicle is misfiring. When you put a greater load on in a higher gear, it takes all the that ignition coils can deliver ( the SHO motor has DIS or coil pack ignition )I worked on the SHO manual transmission equipped Taurus when they were new at the dealer. They should have a lot of power. When was the last time you replaced your wires, plugs etc?
Generally, the whole cable needs to be replaced. If Ford has stopped making them, you can try to do a search on PartsVoice.com to see if someone still has a new cable lying on the shelf somewhere at a dealership. The next option is to find a good quality wrecking yard that can do a nationwide search to find one.
The Check Engine Light Code(s) must be cleared. On this vintage Ford Escort you can disconnect the Negative Battery Cable for a minute or so and that should clear them if there is no other problem. The code 172 is usually an Oxygen Sensor 'not switching code' though, so the DPFE Sesnor will not help that.
It could possibly be that your heater core is seepng coolant and it is going out of the A/C system drain hole which can be near the area of the transmission. Do your windows ever get foggy when you turn on the defroster?
I have found that the InterState Megatron Series provides exceptional cranking power, usually more than the factory batteries. Also, Interstate has an excellent warranty that will tow you and even put you up over night in a room if your Battery fails on a trip. Joe Gibbs, the ex-Redskins Pro football coach and NASCAR winning owner is part of the company. He really cares about the product and makes sure that the quality stays very high.
I have done a couple of engine jobs on Aerostars and I pulled them through the front. You have to remove the grill, radiator etc. but it can be done. Pull off the intake mainfold so you can get the arm of the cherry picker under the windshield and chained up to the long block. It can be done.
How many cylinders does your car have? Once it starts how does it run? Is there a Check Engine Light ever on? How many miles are on the car. Has this mainly happened when it got cold or did it do it during the summer as well?
How many miles does your Ford have on it? If the vehicle has a lot miles, sometimes it is not a good idea to flush out the trans. It is important to use the correct fluid, many of the later Fords use a Mercon5 Synthetic fluid. It sounds like there is a temperature problem with the High/Reverse clutch which is usually the first to wear in a Ford Auto trans. ( I used to rebuild Ford tranny's in Ford Dealerships). Let me know about these questions.
What engine is this Suburban? I ask this because some of the GM truck motors had problems with their injectors leaking. Does your engine say Vortex on the top?