2000 gt shifting weird

I really don't know much about cars, or driving (I just got my license about 4 months ago), so bare with me... I've been driving this car about 40 miles a day every day since then, so I know what's normal and abnormal. When I first got the car, it required a new mass airflow sensor to pass emissions inspection (the service engine light was illuminated). I got it replaced, then a couple weeks later, the engine decided to shut off at a stop sign. Sometimes, I have trouble starting my car. It won't start until I get out, open the hood, then close the hood with a little force. I did this after it died at the stop sign, started it, and proceeded up a hill. It died at the top of the hill. I let it sit for a little bit before making the push to the mechanic. It made it up and down all the hills, died once around a corner, but started immediately and made it to the mechanic. The service engine light was on; he scanned for codes and it was apparently the mass airflow sensor again. They replaced it for free and everything's been "smooth sailing" since then. However, the car's been performing differently since then. Again, I don't know much about cars, but the transmission seems to be malfunctioning. Is it normal for the car to rev up to 3000 rpm trying to reach 30 MPH? Also, on the highway, the automatic transmission seems to be shifting strangely. Instead of immediately switching gears, it will like, stop for a couple of seconds before switching. It's hard to describe what I mean... but it's as if it needs to think before switching to the next gear. :P I checked the transmission fluid while the engine was idling and it seems fine. The car has about 152,000 miles on it. Sorry if this question was confusing. I don't know hardly anything about cars, but don't be afraid to use big words because I can google like anyone else on the planet. :P

Welcome to the forum!

It is a good practice to disconnect the negative battery terminal when you perform any repairs on the engine, specially with sensors. Did the mechanic do it after replacing the second MAF? If not that would be a good thing to start with.

The PCM relies on a good working engine in order to control the transmission and improve shifting strategy; if engine is not working fine, the transmission won't either. In your case all sensor are good and the MAF is new, but the computer "learned" to work with the old MAF and needs to re-learn the new values.

Oscar.

I'm not sure if the mechanic did this-- I was sick at the time, so a friend drove me home and picked me up once it was repaired.

That makes perfect sense. I bought the car off my father, and I'm pretty sure he drove it for quite a while when the MAF sensor was bad. I guess the only thing that seems weird to me is that it wasn't doing this after I got it replaced for the first time. Is there anything I can do to resolve this, or should I just give it some time? Should I refrain from driving it hard?

Try disconnecting the negative battery terminal for 30 minutes, that will clear any information from the computer. After that put everything back together and take it for a test drive, hopefully that should do it if not, then will see what else.

Oscar.

Hey, sorry it took me a year and a half to respond. :P I tried what you recommended, in fact I disconnect my battery about once a week to clean the positive terminal because it gets so corrosion on it that it makes it difficult to start the car sometimes.
The first time I disconnected it, the car was actually good for a day or two. It was performing well and running more like what I was used to. However, it's since gone back to doing what it was doing before. As a side note, it seems to perform a little better at night, and worst when it's extremely hot out.

So the original issue has not yet been resolved?

Try disconnecting the MAF sensor and driving it like that to see if the trans shifts normal.

Not quite. :P I mean, it's slightly better, but the problem's still there. And okay, I will try that. Will driving with the mass air flow sensor unplugged mess up anything? And if it means anything, I noticed today in the drive-thru that the body's shaking a bit more than I remember it.

Do you have any idea of what brand was used to replace the MAF (or MAFs)? Cardone remanufactured ones are crappy and even when they "work", always have problems...

Running the car with the MAF disconnected won't affect anything, it will trip a Check Engine Light bu other than that you'll be fine. What it does is forcing the PCM to relly on other sensors (IAT,ECT and MAP) to determine the correct fuel mixture instead of using the MAF. Follow Tim's advice, it will definitely help you find out if that sensor is your problem.

Oscar.

No, I really haven't the slightest idea. :/ If I need to get it replaced again, what kind would you recommend? Preferably something that I can afford. :P

And thank you, I will try that tomorrow morning.

I had a 99 buick 3800 in the shop last week that had intermittant issues stalling and running bad. P0102 was stored in the PCM. I couldn't get it to act up, but popping the hood revealed a remufacutered aftermarket MAF sensor. So I cleaned the MAF, and wrote on the ticket "may need replacement OEM MAF sensor". HAHA

Again, sorry it took me forever to respond... anyway, I drove the car for a few miles with the MAF sensor unplugged. At least I believed it was unplugged... we unplugged the set of wires directly connected to the sensor in the front. I thought that an SES light was supposed to illuminate when it's not plugged in, but it never came on... the car drove slightly worse than it did with the MAF sensor plugged in.
The problem's actually gotten a little worse since my last post. Now the RPMs fluctuate up and down by about 500 in a rhythmic pattern while coasting. When I have to accelerate rapidly to pass someone suddenly stopping in the middle of the highway, it revs up as high as 6000 RPM, which it had never done previously. It also seems a little hesitant when driving up slight hills (it's fine going up steep hills).
:/
I feel like I have a ton of complaints, but I worry a lot because I don't want to completely ruin something since I'm quite financially limited. :P I just pay really close attention to things that seem unusual.