Hello all,

Attempting to do some maintenance with a 2000 Pontiac Firebird 3.8L V6 I just got. I have a few evap codes, I wanted to know if any of these linked together in any way, and where I should start looking. The car has a strong smell of gas on startup/running, could an exhaust leak cause an EVAP system leak? Could the cats be bad and causing this?

P0404 - EGR Valve Circuit Performance / Actual Position Less Than Commanded
P0440 - Evaporative Emission (EVAP) System
P0442 - Evaporative Emission (EVAP) System Small Leak Detected
P0446 - Evaporative Emission (EVAP) Vent System Performance

And a side code that I didn't even know was an issue, but: P1870 - Transmission Component Slipping. I'm not too worried about this one though just yet.

Thank you for reading, and helping out if you can.

How is it running? That tranny would have me concerned.

She runs pretty good, no misfires or any signs of it. The transmission code surprised me, honestly thought there was nothing wrong with it. Something worth mentioning though is that a few rare times I've went from R -> D and it hesitates, then dies.

How many miles on it?

All the time or just when running cold?

No, unless exhaust is somehow leaking on some part of the evaporative system and has burned a hole in it or somesuch. If it'* not all botched up underneath then this is unlikely.

If "this" = "strong smell of gas" then maybe.
If "this" = "EVAP system leak" then probably not.
If "this" = [all those codes] then no.

Probably valve servo is probably bad, or gummed up. Fix this regardless. It'* easy on the 3800S2.

Could be as simple as a bad gas cap. That'* where I'd start.

I would worry, unless you aren't driving it at all. Ignoring this could take you from unnoticeable slip to overhaul pretty quickly. It could also be that there'* no fixing it without an overhaul already. If you clear codes and it sets again reliably, clear the codes again, choose 3 instead of D, and drive the same way and conditions and see if it sets. If not, then select D and drive the same way and conditions and see if it sets. If it does, we can help troubleshoot further.

Might be the IAC, but I'd start by checking fuel pressure, ignition on engine stopped, then engine idling, then engine idling with the vacuum line disconnected from the fuel pressure regulator (and capped off).

Oh, and while we're here: Change the fuel pressure regulator with a quality unit from Delphi or similar. If you don't know the history of the current one then get this out of the way.

I have no idea how to quote like you did, bare with me lmao... I appreciate your help.

"How many miles on it?"
-> 304,460 on the clock. I honestly didn't believe it at first, I bought it for $200 running and driving and have driven it all over Texas, all it has needed is an alternator thus far. She was a farm/traveling car most of her life.

"All the time or just when running cold?"
-> All the time. Few seconds after startup and continuously through the engine cycle.

"No, unless exhaust is somehow leaking on some part of the evaporative system and has burned a hole in it or somesuch. If it'* not all botched up underneath then this is unlikely."
-> With all the miles.. I wouldn't doubt it. She has a pretty heavy oil leak coming from somewhere (the undercarriage/oil pan is soaked and junked in oil).

"Probably valve servo is probably bad, or gummed up. Fix this regardless. It'* easy on the 3800S2."
-> Perfect, I'll check this out tomorrow and get back to you.

"Could be as simple as a bad gas cap. That'* where I'd start."
-> I'll definitely have this sorted too. I remember having a bad gas cap on a mustang I used to own, all it threw was the "small leak" code and it just needed a new gas cap. I just got a little worried since this car threw more than one code relating to the EVAP system, but to be fair it probably deserves a multi-point inspection of every system around the car..

About the transmission code, I don't drive it daily. Honestly have been thinking about pulling the engine and resealing it, just as a fun project to do (pretty much the reason I bought it), or swapping it with an LS1 or LS3 if I wanna go all out. With all of the miles on the car, I figured your advice would be best here in what to do. Since the transmission is on the way out too, it'* probably best to do an engine/transmission rebuild/swap at this point.. Something worth mentioning too, I tried flushing the cooling system twice, but the whole system is very rusty even after flushing with proper chemicals. Probably OE cooling components, I wouldn't be surprised. When you open the radiator cap all you see is rusty walls. I don't even want to think about the thermostat lol.

The car is honestly in pretty decent condition for 300k miles. I know these engines are pretty indestructible. You might think this car is just a junk POS, and it might be, but hell this is my first real project so I'm excited to take it on.

What are your thoughts? Thank you.

The oil leak is probably the oil pan gasket.

I wouldn't say the transmission is on the way out unless there are other issues that I haven't heard of. Slip might be solved with a fluid/filter change and maybe a shift kit.

I don't think it'* a POS. The ones that last this long prove the opposite!