p172 2001 buick lesabre limited

this buick has about 210k miles--the MAF was replaced, it was diagnosed as bad, MAP replaced, i broke it, IAC a just in case replacement and IAT replaced. After replacing the MAF and MAP the car ran very well. I then had the upper intake manifold replaced to avoid any issue with leaks and shortly after noticed the car had a hesitation to it while at idle. I also noticed that when i started it would rev up to about 1300 rpm then reduce to about 1000 and when got down around 700 rpm i could feel it kind of chugging. It also seemed to do it more going up hills so i thought a fuel filter would help. i changed it and under advice from friend ran a can of sea foam through it and almost immediately it start chugging. I drove it hoping it might come out of it but it didn't so i changed the filter again with no luck. the old filter was not bad. a local shop hooked up their snap on scanner no miss fire codes and no other codes found. The after about a month it started with the p172. I came across a scanner danner video that suggested checking fuse for o2 so i did that and ok. I have a vom and code reader for my diagnostics. it did get a loaner fuel pressure tester and with key on engine off got 56psi and with key ok engine running 50psi with a little fluctuation to 48 psi but no lower. i am not sure where i can go from here with my limited diagnostic tools so any help is appreciated!

Are you familiar with reading fuel trims? It would be helpful to know if this is really a one bank issue or if the others is also rich, just not quite rich enough to set a code.

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According to the Snap-On Troubleshooter, normal fuel pressure at idle is 48-55 PSI, so your readings look good so far.

Unfortunately, without access to scan data, this will be a tough one to diagnose accurately. Does your code reader show data at all? Global OBD data would be enough for our purposes.

The good news is that you can only get a rich trim code (P0172) in a limited number of ways. Either the engine is getting too much fuel (fuel pressure, sensor inputs, ect), or the engine believes it's getting too much fuel (lying O2 sensors). You've already tested fuel pressure, so we know there isn't a pump problem.

My first thought is a leaking fuel pressure regulator. The internals fail and allow fuel to get sucked into the vacuum hose for the regulator, straight into the intake. The easiest way to check for this is to idle the engine and pull the vacuum hose off the regulator. Any liquid fuel in the hose, or fuel coming out of the regulator is grounds for replacement.

no fuel in the pressure regulator--i will look into the scan tool as mine is very limited--i did notice today though it didn't seem to have the symptoms as much--i had messed with the spark plugs wires will check everything just to be sure and today drove it over 100 miles with no code--i had cleared it with my reader.

Theres some ground wires that connect down by the negative cable near the starter... clean up the eyelets and contact surfaces and put the back.. there may be another under the ignition control module on this car, do the same

You said the intake manifold gaskets have been replaced? Have you checked for other vacuum leaks as well? Even though the manifold gaskets have been replaced, I would double check around the manifold to be sure.

no fuel in the pressure regulator--is there a scan tool that anyone could recommend? something simple for an entry level diagnoser. my current code reader does not provide any other info beside the code,

You can order a Bluetooth dongle for your phone for about $10 and download a free or low cost app like torque pro for $5 that will get you what you need.

Search Amazon for obd2 dongle and buy one with good reviews. Search obd2 in your phones app store.

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i pulled the fuel rail and checked the operation of the injectors and they seem to be firing fine--no drunken piss type of discharge--i did get a zurich code reader that can do live data here are some screen shots as i couldn't do video and upload it. i am not real familiar with fuel trim, yet, so any further advice is appreciated.

i have seen people use brake cleaner or propane to check for leaks. is there a safer way to test for these? I have a zurich code reader that indicates the maf and map sensors are working. I am getting stft bank1 anywhere from -2.3 to 4.0 and ltft fairly steady around -14.7. I have checked my air filter for any clogs. the o2 senors volts is about 0.795 down to 0.15.

so today i pulled the plugs to see what they looked like and have attached some photos. The 5 &6 look alike and the 3&1 look similar. none of the 2&4 but they looked more like the 3&1. I don't know if these indicate bad injectors but definitely something going on. possibly related to the p172 but not sure. i also looked at the map sensor to be sure gaskets were in there etc. after i got everything back together and ran the engine my assistant shut off the vehicle and i heard a sucking sound coming from the map sensor. i had them restart and shut down again while touching the map sensor and could feel it.when it is running there is no vacuum leak here so not sure what is going on. the pcv did have it's gasket and there was some oil in there but i don't know if that is normal or not.
thanks for the help and suggestons.