Ah ok Deekster...a code for the EGR would make sense. I spoke to two mechanics, with whom i am good friends, and they keep thinking it's a vacuum leak, even though i couldnt find one. I do wonder though, that fuel evaporation solonoid, is it some kind of open/close mechanism? I know that's a stupid question but I'm just making sure. I wonder if mine has somehow gone bad and is letting in more fuel vapor than it should and that's what's making my idle crazy at least. That still doesn't explain a vacuum leak BUT, my idling problems never came around until i re-attached a vacuum hose onto that fuel evap solenoid.

We'll, im going to go out to the garage and try a few things...

The fuel EVAP solenoid in this case is Open or Closed depending on how it is commanded.

Read On.

From the FSM a DTC P0171 could result from the the following:
Fuel pressure too low and result in poor performance.
Have you checked the fuel pressure for proper readings yet. Or do you have all the vacuum lines hooked up correctly, especially to the fuel pressure regulator.

As far as the EVAP system goes, When the engine is running, the fuel vapor is purged from the carbon element by intake air flow and consumed in the normal combustion process.
The EVAP purge valve allows manifold vacuum to purge the canister. The PCM supplies a ground to energize the EVAP purge valve (purge on). The EVAP purge valve control is is Pulse Width Modulated (PWM) or turned ON and OFF several times a second.
The PCM controlled PWM output is commanded when the appropriate conditions have been met:
1) Engine coolant above 77* F
2) After the engine has been running about 3 minutes on a cold start or 45 sec's on a warm start.
3) The vehicle is operating in closed loop fuel control.
There is quite a bit more, actually more than I can get into here on this site.
You would need an FSM as there is much more to this topic than I realized. Another page full of data on the operation and diagnostics of the EVAP system alone.
Sorry I can't help much more than this. You'll need to get an FSM for your year vehicle as this data comes from an 1998 book and am not 100% sure it is the same for your car.
I guess for a "Quick Question" there is no quick answer.

Thank you Rick that is all very educating information. It makes sense. In reading that and checking the EVAP solenoid, everything appears to be working correctly with that system. Thank you very much again!

Updates after fiddling around for an hour and a half:

-EGR appears to function normally
-IAC valve is a little dirty but functioning (didn't have the tool at home to do this so i couldn't clean it while it was out prior)
-MAF is clean
-EVAP solenoid works correctly
-Fuel injectors do not appear to be the source of the vacuum leak

After much thinking and observing the past few days, I've also concluded the following:

-Cray idle and SES only occur during operating temperatures
-Crazy idle will come around most often when coasting or idling in drive
-Crazy idle seems to be triggered by a sudden release of the gas pedal


I know this is going to add to the confusion, but I have other thoughts:

Perhaps the fuel pressure regulator is going bad? I have a fuel pressure gauge to attach to the rail but won't be able to test until tomorrow, and only if it's not raining (complicated garage situation). if the regulator is going bad, would that not explain the crazy idle and lean sensor readings? I don't think this would explain why it's so random, but I'm not sure.

Maybe the oxygen sensor is simply bad, so when it reads lean it's dumping too much fuel into the cylinders, causing the idle to jump and fall?

I'm sorry this so hard to keep track of, but I like to get all my thoughts down at once while I'm remembering them lol. Thanks guys!....

This is where a diagnostic tool would help you.
You could be monitoring the O2 sensor, the air/fuel ratio and fuel pressure at the same time and make a more educated assumption.

I agree, but no one around here can do it. I was lucky to find the guy that could even read my computer's codes. He's kind of an @$$hole though so I don't think I'll be heading back there.

It'd be nice to get a hold of something like that....then I could handle all the computer crap myself...

Back again. Just wanted to point out something I noticed. My vacuum/boost gauge at operating temperature, in drive, and idling, is only 17 HGin (orwhatever that measurement is. Also, I'm only getting 6 lbs of boost which i find to be coming up short compared to most people. Both indications of a vacuum leak. At this point, because of all the testing, poking, and prodding I've done, as well as some professional opinions, I've decided I do have a vacuum leak. Now I just have to find it. Next, when I get a free hour or so, I'm going to replace my injector rings/gaskets, because I didn't do it when I replaced my supercharger coupler quiet . I'm also thinking of trying to retorque my supercharger bolts to make sure that gasket isn't leaking, even though a spray leak test didn't show any. We'll see what happens...more later...

I know I haven't posted in a while, but of course, this issue is ongoing.....

It's getting bad. The idle fluctuations are more common than ever, the engine light doesn't stay off for long....sigh. But, I think I made some headway. I noticed when I got the car that some of the engine block in various places looked wet. I knew my valve covers needed done so I assumed it was oil and moved on with my life and changed the valve cover gaskets. Well, I checked it out a little bit ago and it appears my engine block still looks 'wet'. I noticed my engine coolant has gotten pretty low in the last 3 months. Maybe like an inch and a half of it's level. That's a lot. I've come to a conclusion...

...since the car runs fine under load/throttle/whathaveyou, I have to assume my lower intake manifold gasket is bad. Therefore also causing a vacuum leak, causing my oxygen sensor to get insane.

Does it make sense to anyone?

I guess that's possible, but in my case (I have a confirmed LIM gasket leak) the first sign that the LIM gasket was going bad were deposits found on the spark plugs, from coolant seeping into the cylinders. That was at least 30k miles go, and so far none of the symptoms you're describing.

I think I'm just going to take a few days off in a week or so to get this done right. Kinda sucks though - I wish I would have done it when I had my supercharger off to change the coupler. I was like, two steps away. Oh well...at least I know how to get to it. I printed out that write-up to get my supercharger off so I'll just pull that printout out from the 'ol file cabinet. I just replaced that supercharger gasket too...

Anyway, I guess I'll have to get a supercharger gasket, LIM gasket, and fuel injector gaskets. I had a suspicion the fuel injectors might be a source of vacuum leak too. Screw it...I'm just going to replace everything. To me, this kind of work is fun anyway. I really enjoyed changing my coupler, so this will just be a slightly more involved extension of the same thing. I wish I didn't have to do it, but I will.

Anyone else think this is a good route to go? It COULD fix the problem I guess....maybe...

The LIM gaskets are certainly a likely contributor to your low coolant situation. But to your fluctuating idle - it could be a vacuum leak, or simply a dirty MAF. Make sure you clean the MAF with MAF cleaner while you have everything apart.

Yeah I undersdtand you completely AA, but I'm only replacing the LIM gasket, supercharger gasket, and injector o-rings. Even, if for some reason, it doesn't fix my idling and O2 sensor issue, it needs done anyway so I won't REALLY be wasting my time. But at least I'll be able to potentially eliminate it as a source of vacuum leaks! That's another reason I'm doing it.

As for the MAF, it LOOKS clean and I clean it every month or so just to be safe, but that's not to say it isn't bad.[/i]