I bought this 2000 Pontiac Grand Prix about a year ago with 200k miles on it. I knew it was going to need work. So far, Ive done little minor things to it. Replaced a rotted sway bar, fuel filter, a broken driver side power window, and given it an oil change to name a few. I have a new EGR valve to put in it but, Im stuck on a PO171 trouble code right now. It wasnt until I had it taken to a mechanic that I started having big issues with the car. I tried to clean the throttle body about a month and a half ago and barley bumped a fuel line when the fuel line snapped. I had put some JB Weld type putty around the line to do me just until I got the car to the shop. That worked. Drove it up to the shop with no problems. I explained to them what had happened and told them the line with putty around it would be the one needing replaced. I got the car back, got it home, noticed white smoke flowing out from under the hood, lifted the hood, and seen that the return line had been replaced and not the sending line as I had talked to them about. After an understanding phone conversation with the mechanic, we chalked it up to a miscommunication issue and they agreed to fix their broken part for free. It was just an aftermarket line and the guy who worked on it missed the clip that locks the bell over the line when the line "engaged". The puttied line (even after all the trouble with the return line) still had putty on it and was still working decent. It began to leak very tiny amounts and I decided to fix that line myself. I believe it was another aftermarket line that I bought, got it installed by clamping it down to the other side of the line. It works fantastic now. No leaks. That was roughly a month ago and Ive had no problems out of it since. Again, Ive had the car for almost a year now and Ive put a good 20k miles on it. Never, since the day I bought it, has the CEL come on until two days ago when I was driving it. Plugged it up to my ODB and got a PO171 code. System too lean. After talking around with a few skilled mechanics, Ive heard that the repair amount for a shop to do it is a little out of my price range and since Im not the worst person to ever work on a car, Ive decided to do the repairs myself and save a little money. After doing a little research, I found that the main two issues with a PO171 code is either a vacuum leak or a faulty MAF sensor. The MAF sensor seems to be doing its job so, Ive moved on to a vacuum leak. I installed a new thermostat in it a couple weeks ago and noticed a plug that was hissing while the car was running and unplugged it. The car stalled out immediately after unplugging it. Looking at the position of the plug and why it was hissing, I would say it was some sort of "air valve". This plug is located on the throttle body assembly, just below the air control valve. It has two tubes coming from the boot, one to the fuel pressure regulator (I believe) and one going horizontally straight across the engine into another little box (Im not sure what that box is but, it has a sensor on it). Judging by the line coming out of the other end of the box, I would say its something to do with the EVAP system as the line coming out has a green twist top in the middle that says "EVAP" in small letters on it. After inspecting for a vacuum leak, I noticed that the boot that connects to the throttle body assembly is split from the top to the bottom and fits in very loosely. Where one line connects into the "EVAP black box", its bent and looks as if it may have a small crack or two in it at that bend.
My question is: What is that plug? What is that box called exactly? What does that entire system of tubes do? Could those cracks and splits be whats causing my PO171 code?
To add, these are my ODB's results after 5 minuets of idle:
FREEZE FRAME DATA
CALC LOAD (%)- 1.57
STFT B1 (%)- 20.31
LTFT B1 (5)- 16.41
MAP (INHG)- 11.22
ENG RPM- 691
VEH SPEED (MPH)- 0
MAF (LB/MIN)- 0.42
TPS (%)- 0.00
FUEL SYS 1- CL
FUEL SYS 2- CL-FAULT
Ive heard that the STFT and LTFT results are off and may indicate a vacuum leak. Im not sure what CALC LOAD (%) should be at or why people keep asking me if thats what I really got like they are surprised either. And Im not sure wy FUEL SYS 1 says CL but, FUEL SYS 2 says CL-FAULT either.
The car starts just fine with no hesitation, Ive tried not to drive it with that trouble code stored because Ive heard that too much driving on it could hurt the engine and I want to get the most out of this engine before it completely breaks down.
Any help would be much appreciated at this point! Thanks!