LS fuel codes: Offer your opinion/recommendations?

[LSally]

Hey guys, I DID check some older threads about some of these codes but I think my symptoms are a bit different so I thought I'd start fresh.

2004 LS 3.9 auto VERY well maintained.

FYI I know the battery condition can effect these codes and I was told like a year ago that it may need to be replaced soon, but never had any symptoms, even when leaving it to sit for weeks.

Car idles a bit off, and is sluggish but sometimes will leap off the line without warning. Also has the clacking noise coming from the console area that johnieboy13 was mentioning when he had this issue. (sounds like the tranny to me, so probably separate but thought that might be something to mention) No misfire codes (I suspected coils) only these three: P0190, P0174, and P0171.

Possible MAS sensor, fuel pressure sensor, fuel filter or maybe the fuel pump.

Where would you all start replacing parts? Its like you're shooting in the dark but each round is costing you $98!

 

[G-RELL]

my money on...coils and bad cats

 

[joegr]

I'd check the fuel pressure sensor (P0190). Either it is bad, or the pump can't maintain pressure. The surest way to do this without throwing a fuel pressure sensor at it, is to use a scan tool to read the fuel pressure while checking the fuel pressure with a mechanical fuel gauge. If both reading are the same (but out of the correct range) then you have a fuel system problem somewhere (clogged filter, bad pump, bad transfer pump, ...). If the two readings are different, you have confirmed that the fuel pressure sensor is bad.
The other two codes are probably the result of the fuel pressure not being what the PCM wants or believes it to be.

 

[LSally]

Update:

Took it in to get a pro opinion and they said it is holding pressure fine while driving but dipping down after shut off. Apparently they said it should hold pressure even when not running, and they suspect the jet pump. I thought before I sell it I would just replace both the jet pump and the fuel pump together (as recommended) and see how it performs.

Anyone know where to buy these parts short of the dealer? I found the fuel pump new but can only find the jet pump used.