First post here, what a doozy.....Anyway, not new to forums by any means, I have a build thread with over a million views on F150forum and own nothing but Fords.

Bought this truck with 101k and zero maintenance has ever been done. It's a 2001 RWD flex fuel 3.0. Started on the maintenance items due to rough idle and failure to start at times. Runs pretty good now, but still has a rough idle once in a while. So far I have replaced the items below, but today, I have gotten a P0172 repeatedly after clearing it twice and its back again. Also got at different times today a P0303, P0305, P0306, but those have cleared and stayed gone.

Tests so far include the dry fire injector test (turn ignition to start, hold down gas pedal, turn ignition to run) and the truck just cranks, let off gas pedal and it starts right up. I have seen that is a test for leaky injectors.

Inspected and sprayed brake cleaner near all vacuum lines, no change to idle speed.

Unplug IAC and truck idles down but still runs, plug in and it idles back up, same with unplugging MAF

These are all things I did as maintenance when I bought the truck 3 weeks ago to get the truck to where I thought it should be mechanically, not as a result of any codes:
Transmission fluid and filter - Wix filter & gasket and Motorcraft Mercon V fluid
IAC - Hitachi
Coil, sparkplugs, plug wires - all Motorcraft
Cleaned MAF and Throttle body - removed throttle body for this
Cam position sensor and Cam Synchronizer - Motorcraft
Air Filter - Wix
Fuel filter - Wix
Oil and filter - Pennzoil full synthetic 5W20 high mileage and Motorcraft filter
PCV - Standard Ignition
Coolant flush, new thermostat and temp sensor, both Motorcraft, Prestone antifreeze
Both upstream O2 sensors -Bosch

At times the truck idles and runs perfect, sometimes it idles really rough and shaky without codes showing.
I have read to swap the 2 new O2 sensors with each other to see if the code switches to the other bank, to replace the upper intake plenum gasket, replace the MAF, etc. I just want to know what tests I should try using a nice scanner I am getting from my son tomorrow. I think testing STFT and LTFT tells a lot from what I have read, but I don't know how to interpret those results nor do I have a smoke machine to test for vacuum leaks (although I think the IAC test I did rules out vacuum issues). All help is appreciated! Thank you, Jon

 

Looking back through my notes, 1 week ago I had a P0175 along with a P0303. I cleared those and they haven't came back. So those are both bank 2, the P0172 with P0305 amd P0306 are all bank 1, hmmmmm. I am not driving the truck much, just around the block a few times since its not tagged and has 13 year old tires on it.

Yes, so it looks like I am having misfires on both banks with both P0172 and P0175. I'll monitor MAF data this evening.

Seems odd to have a P0172 (bank 1 rich) passenger side along with misfires for bank 2 driver side (P0305 & P0306). Then 5 days ago had the opposite with a P0175 (bank 2 rich) driver side along with a P0303 misfire cylinder 3 on the passenger side.

 

these motors are known for burnt valves so a compression test will answer that. test with cold motor all plugs out. theres lots of info out there to understand info that a scanner will put out. test with motor warmed up to running temp. it takes a bit of time to get the O2 sensors to work. look at LTFT and STFT O2 sensors volts. i'll see if i can find a good YT link to understand the info.

 

Well got home and had to update and charge then scan tool. Decided to double check plugs and plug wires while letting the system reset by unhooking the battery. Checked all vacuum hoses again, decided to clean the MAF again and managed to break a wire in it somehow. No biggie, planned to replace it anyway. Also went to remove the EGR valve pressure sensor and immediately snapped a brittle nipple off into the hose. Removed both hoses and one had a bunch of gunk in it. So I decided to call it a night and go to town tomorrow for replacements.

 

Update! Decided to go get replacements for the MAF and EGR pressure sensor. I also for the first time since doing all this work, disconnected the battery for a couple hours. Got everything installed, went through the relearn process at idle, let it idle for about 30 minutes all while monitoring live data, then ran a report. Went for a drive around the block 4 times and ran another report. Zero DTC's, no misfires, no injector faults, MAF was reading around 4.8 gps and it is running perfect!