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ok i replaced my bcs and the car started boosting again but it still throws the p0171 code whick is system too lean bank 1. I found a vacuum leak at the vacuum line frome the vacuum tree to the FPR, but i fixed it and i dont know where to go next. i hooked up a scanner to my can and the stft were 20.3 and the ltft was 16.4, what exactly does this mean and where do i start next. I also noticed i had a slight gas leak but that just came around and the system lean have been around for like the last year. Any help at all would be greatly appreciated.

does the car have any other symptoms, bucking, stalling, loss of power.. I had the same code, and the same LTFT, but my car also had the other symptoms.... I changed the mass Airflow sensor and things went back to normal, no lean code and fuel trims were good... Just my 2 cents... If u have another try changing it out, getting one from a jy..

my engine does surge alot sometimes and my boost guage barely ever seats at -10

There's a leak or bad sensor somewhere. Try scanning the throttle position sensor to see if you have any dead spots in it.

Get a scan of the MAF, LTFT & STFT at idle & again at 2,500 rpm. You can get the scans while in park.

What does these number mean and thanks for the help so fa,r but more is needed thanks in advance. Also when i scanned the codes yesterdat i got the p0171 of course and i got p0122 (throttle/pedal position sensor a circuit low input and a code that said low input to the maf sensor i cant remember what the number was. Please help
idle
MAF: 0.55
STFT:20.3
LTFT:16.4

2500 RPMS
MAF:1.59
STFT:0.8
LTFT:16.4

also when i start my car for the first time in a while it starts popping under the car in the converter area and int the back by the muffler what does that mean.

The Short Term Fuel Trims can range from -20 to +20 & the Long Term from -16 to + 16. Ideally they should be very close to zero.
Trims on the + side mean the PCM has increased the fuel trims (added fuel) to correct what it sees as a lean condition.

Lean conditions can be caused by too much air getting into the manifold or too little fuel. You could also have a false lean condition caused by a faulty sensor.

I'll get a scan tomorrow & see if we can rule out the MAF sensor. Since your STFT gets better at higher RPMs I'm betting on a good old fashioned vacuum leak being your problem.

Well until tomorrow i will be spaying carb cleaner, thanks for the info.

How old is your fuel filter? Could've become clogged and restricting the system.

my fuel filter is about 2 months old

i think im leaning toward needing a fuel pump cause i dont notice any other problems what do you guys thin

going back on what LeSabre in Buffalo said my TPS sometimes reads 0.0 and other times it reads 0.4 at idle

I think you should replace the TPS and see where it gets you. I know harofreak00 has some, not sure if a 96 TPS is the same as 00+, however.

Have you checked your fuel pressure? Fuel pumps normally either work or don't. There are instances when they get weak, but it's not terribly common.

i reoplaced my TPS and it got me nowhere it still sometimes says 0.0 and im gonna bet my fuel pressure checked today an let you know what i come up with

Here's what I got on the 98 SSE:

Idle (around 830 RPM)
.55 lb/min
STFT .8
LTFT 7.8

2,500
1.72 lb/min
STFT -1.0
LTFT 3.9

If you had low fuel pressure then I would think the trims would get higher with higher RPMs. I'm still going with a vacuum leak. Looks like I might also have a small leak.

thanks i will keep looking and can you use mass airflow cleaner to find leaks

Probably. It's expensive.

that MAF figure looks low for 2500 RPM. Try unplugging it to see if your LTFT's improve.

MAF values didnt improve they jumped into the 20s i have been checking and ckecking but i cant find anything but im not gonna give up yet. Are there any other sensors that would contribute to this cause and, Thanks again for the help.

LeSabre in Buffalo wrote:Probably. It's expensive.

that MAF figure looks low for 2500 RPM. Try unplugging it to see if your LTFT's improve.

While the sensor is unplugged take it for a little spin and see if the car runs better with the MAF sensor unplugged... Your fuel trims will still be wacky with the sensor unplugged but if it makes the car run the way it should then it could be a likely cause... if when u plug the sensor back in the old symptoms come back, then i would try a different known good MAF and see if that does the trick... Just cleaning the old sensor will not work..