98 Scab XL 4.6 (romeo) 4X4 250K miles. I've been working on this for a year- truck was running great with a bit of a miss. Last week, All of a sudden, the truck had no power. could barely get up to 30 mph. I have changed the fuel pump, thinking that was the problem, since I had already changed the Fuel Filter, IAC, TPS, EGR, PTFE, plugs (motorcraft), wires and coils and have less than 500 miles on the truck since I got it. Also have changed out the vacuum lines that were dry rotted.
Was throwing P0171/4, Evap, Bank 2S2 and random misfire codes. I then thought, since the truck was running like it was constipated, that the Cats were clogged so I had them cut off and straight pipe welded in. The upstream bank 2 cat was in pieces and the downstream cat was clogged with them. The only code I am getting currently is P0174- Bank 2 lean condition. I have previously done a compression test, getting between 80 and 120, which I know is low, but trying to make the engine last until I can build another and install it if needed.
Trouble shooting steps: Code reader, live data looks like it may have a bad O2 @ B1S1. Intermittent 0.00 readings while all the others cycle normally.
Pulled all the plug wires and checked for spark. Same with injectors. Only half of the cylinders made a difference in the running. Cyl 1, 2, 3 and 7 do not make the engine run worse. the others do. Listened to all the injectors and they seem to be working. Checked the inertial switch and it is fine. I've got spark and the misfires-even they don't show as a code are not isolated to one coil. Will run another fuel pressure check tomorrow to eliminate that as a possible cause. I removed and cleaned the throttle body this week and it made no difference.


AAARGH! I'm at my wit's end , please give me something else to look at- Maybe the PCM? the Fuel Pressure Regulator? WTFIWWTT?


Thanks in advance for any help/advice you can give

 

With those compression readings, I'd be looking in the cylinders with a borescope. You may have filthy fuel injectors.

 

I didn't know injectors would affect the compression? I've listened to the injectors with a stethoscope and all seem to be clicking the same frequency and volume.
I just went to the parts store and got another EGR (#2), a Cam sensor, a fuel pressure regulator and an upstream O2 sensor for bank 1. I'm going to replace them in this order- O2 sensor, then check for any change; Cam sensor/check; EGR/check then FP Reg/check.
But even with all the parts I've already put on, I still only have less than $2K in this truck. I am planning to keep it for a couple years and give it to my son IF I can get it running and dependable.

 

Filthy fuel injectors won't cause low compression, but they can sure cause a miss and a lean code. If you are just shotgunning parts at it, why not buy a set of rebuilt injectors - or at least get yours cleaned and bench tested.

 

Please take this with respect to you.
Your not troubleshooting correctly.
Repair for the codes you have. 171/174 is an air leak common to 'all' cylinders.
If you don't put order in this you end up in confusion and come to the board for help so please take a break and reconsider..
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If you are able to look at live data, it supports the trouble code/s by showing one or both fuel trim tables out of limits. The 171 and /or 174 codes has to be out of limits for these codes to set. They are linked together in program to do this.
The codes says lean and refers to the Ox sensors on each bank for the codes but does not mean the sensors are faulty.
You may have more than one trouble at the same time. Throwing parts at the motor randomly is expensive, risks causing problems in addition to of what you had, causing confusion if a mistake were made or a part is faulty out of the box.
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Changing fuel pump thinking........ is a mistake without proving if first and is costly, plus labor for no result.
Ox sensor #2 (B2S2) will not cause drivability issue at any time because it is only a Cat monitor. It does not have any control functions otherwise. It's reading usually does not move very much. It ideally should not or a trouble is indicated for large swings in the reading.
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Having a Scanner means you need to interpret the data correctly or your no better off than without one.
Start new and address the codes you have one by one until they are solved for.
Good luck.