p0191 code on my 05 LS 3.9

[sasdesignsny]

Hey Everyone! Steve here from Long Island NY. New to this community. Wish it was on better terms but I just recently got a 2005 LS sport v8. Purchased it from someone that i believe had the car sitting for about a half a year inside garage. kept very clean. First thing i did was after putting fresh gas in, had a missfire/buck while driving. got a CEL and got the code ran which came to be p0191. ( Fuel rail pressure sensor condition ) one of my guys at a shop told me because it was sitting replace the fuel filter, which were my intentions to see what would happen. replaced the filter ( original motorcraft one was pouring out black dirty old gas) after i replaced the filter, car seemed to run a lot better. drove it this past weekend about 35 minutes out east. car sat and then drove it back into town. just as i got up around my block, car had the same hesitation, felt like i ran out of gas and had to get off the pedal so it would regain its composer and got home. The odd thing was my mechanic said when the old filter was in it was prob just like loading up stuck in the filter and then when u shut it down it releases the pressure in the filter and then the car drove fine. Now he is going to check the voltage/psi and everything else to see what the direct issue would be. Do you think that even after changing the filter and filling the tank with fresh gas, it can still be releasing black old gas into the fresh filter to clog it up again? or may it be something a bit more involved? I know the coils were replaced once before but was told that the car supposedly never had continuing issues with coils. I know when a coil is bad it would misfire constantly no matter what so i dont think it would be that. but you guys here know more then me about this. Any input would be extremely helpful. Sorry for rambling on, just wanted to get this issue across the board and see what happens. Thanks in advance.

- Steve

 

[epikls]

Try seafoam to completely clean your fuel system

 

[purevilpleasure]

Replace th filter again, may have to do it one more time.

 

[joegr]

... I know when a coil is bad it would misfire constantly no matter what so i dont think it would be that. ...

You "know" wrong. The way coils fail in the LS is a high voltage breakdown of the epoxy in the coils. This means that they hardly ever fail outright. Instead, they become marginal where they fire most of the time, but miss now and then too. The only way to find these marginal coils is to scope them while doing a stress test. Generally, this costs more than just replacing all the coils.

You may still have fuel system problems and/or a failing fuel pressure sensor, but don't discount the possibility that it is coils. Read some of the posts on here. There are plenty of examples of marginal coils and hard to trace random misfires.

 

[sasdesignsny]

ah ok. thanks for that info. and yeh I think replacing the filter a second time would feel safer to do in addition to what my mechanic may come across in his diag. i usually work on the cars myself but because i just got it i feel safer bringing it to someone that has done work on them in the past so i can learn what is going on. I will check other posts as well to clarify issues. Thanks again guys i will keep posted on this and see if anyone else has other suggestions.