Being that water effects it, I'm thinking maybe something electrical? I don't know. The MAF sensor I will clean first..can't hurt. Being that the spark plug wires are original, that wouldn't hurt either. I'll have to check the coils as well. I keep going back to the transmission speed sensor because some of the symptoms seem the same...and it's right behind the passenger wheel, where it can get wet.

But the MAF sensor seems to be the most likely...unless it is a transmission problem, like the TCC. But the MAF con throw that off, so I"m hoping it's the MAF since that's cheaper....

But I did powerwash underneath the car, so that could spray water in places you don't want it...

Did you check the electrical connections for the MAF? Besides cleaning the unit check for water intrusion at the connector

Water would not effect the maff sensor as much since it is in the upper part of the engine bay. If it was water in any case then it would be the first o2 sensor. I had the same problem with my parents Grand Prix 3100 which did the exact results. Turned out that one of the spark plugs weren't firing giving the same issue as you described (on freeway surges). If it is the Trans, the tcc could be at fault but that is a very expensive road to take, and a fluid change could help. MAF being dirty is rare but possible, but I would go with the plugs first though.

And I also don't get why it's not setting off any codes... You think the check engine light would come on, but it doesn't! That would make this 100 times easier!

On another side note, I noticed the little box that protects the PCM was not closed.... It snaps in place over the PCM, well the bottom of it wasn't locked into place, which created about an inch opening allowing access to the PCM... This is kinda in an area that may get wet if there is enough water (big puddles or powerwashing....) Wonder if that could have anything to do with the water issues?

maybe check everything in that box to see if there is any corrosion and/or moisture? Couldn't hurt and it's free!

Well I have some good news, and bad news. But lets start with some background...

So a few weeks ago I cleaned the MAF sensor and replaced the Vehicle Speed Sensor (since it was easy, and only $15). Well, since then I have had no issues, but it hasn't really rained. I did drive in some hilly areas where it would have been prone to acting up, but it never did.

Now for the good news. As many of you in the midwest are aware, it POURED today. Well at lunch time I was heading to McDonald's near school, and was forced to drive through a deep puddle. I know it got my exhaust wet since I could see it "smoking". Well, it never had any issues from that. No surging or whatever! So I was happy about that.

Now the bad news. Earlier this morning (while it was still dry) I was at an intersection about to turn. As I pressed the gas pedal, the engine revved up like I was in neutral. I looked down, and I was in drive...then it surged forward and took off.

Yeah...I'm getting pretty concerned....

ruh roh...I'm not sure about you, but when the tranny lets go in my Lumina, it's gone.

Wouldn't it be better to get rid of it BEFORE the tranny dies?

Well, I don't want to sell the car knowing something is going wrong on it. I know how sick I would be if I bought a car and the seller didn't tell me something major was about to happen. And of course whoever I would sell it to would probably either be young, or wouldn't have tons of money for repairs. So, I don't really want to sell it.... Morally, I'd feel bad. I know, it's dumb, but I would.

Looking at places like Schram Auto Parts, I can get a used one for just a couple hundred bucks with 30,60, or 90 day warranties. It would just depend on how hard it would be to install... If my dad and I could do it ourselves, it really wouldn't be that bad.

Really, I've been fortunate with this car. Other than routine maintenance, I have really never had to fix much, other than the intake gasket. I've been fairly lucky. Everything else (including the body) is in great shape...so it really wouldn't be worth scrapping either...