cardinexile

Also posted this in the engine builders REa-got no response, so thought I'd repost here ... 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.

cardinexile

Well, I figured it out. Bank 1 Sensor 1 O2 tested bad- Changed it and it made absolutely no difference. Went to the next step, changing the Fuel Pressure Regulator...Success!!! Finally! I saw this as a possible fix on another forum and thought-what the heck, it's a $20 part. Took like 5 minutes. unplugged the inertial switch and cranked the truck to relieve the fuel pressure. Removed the two socket-head cap screws, pulled the old reg off and put the new one on. Plugged the inertial switch back in, fired it up. Runs almost as good as my 03 does now.