'93 Lumina Problem - Rough Ride (And Not the Good Kind)

This just starting happening after getting gas at some station, so I don't know if I just got bad gas or what, but here's my problem (and I checked the other threads, but didn't find anything exactly like this):

The car sometimes is rough when giving it gas, sometimes not. Usually, it's smooth once a stable speed is achieved, or might jerk once or twice. Today, it was rough when I first drove this morning, then stopped after a long ride, but then started again a little after sitting for awhile and driving a few miles. I filled up the tank again (from someplace else) and will see how that handles tonight (I'm at work right now), but I'm not optimistic. I've read the other threads about vacuum tubes and some other possible solutions, but this isn't happening all the time, just a majority. Being my wife's car, I'm wanting to get this dealt with as soon as possible, and figured I'd stop here for some possible advice. Thank you for any help you can offer.

I would have your fuel pressure checked out, check your fuel filter, it is possible you got bad gas but not likely the problem, My 93 grand Prix w/3.1L used to run really rough when it was wet outside till the car dried itself out, I figured out one of my wires needed to be replaced the rubber was worn. its someplace to start. You could have a fouled plug which would make the car run on one less cylinder.. It wouldnt hurt to pull a plug and see how it looks.
-Jimmy

Thanks for your reply, I'll try that. Today, it was rough when I first started it up and drove it this morning, then later smoothed out and was fine. I have no doubt it will be rough again when I drive later, though. If it was a fouled plug, would it be rough all the time, or like it is now? This is on again/off again (but mostly on to be honest). My big problem is that I'm constructing a house now and don't want to shell out a few hundred bucks to a mechanic right now.

It depends on whether the plug is firing or not, the plug could be barely working, My 3.1 had coils that when they start to go bad make the care run like crap, due to irregular spark, also a place to check, I dont remember how much the coils cost me but I dont believe they were expensive. check with a place like autozone they can give you prices. Have you given the car a tune up yet? plugs are pretty cheap, and easy to install. Good Luck.
-Jimmy

Hi.I am new here and going through the same thing with my lumina.Figured it was either fuel injector or plugs.My question though is how do you say the plugs are easy to change.The 3 back plugs are buried under the engine and was going to be charged $400 for mechanic to change them.Would appreciate any shortcuts on this.Thanks.

I finally had to just take it in to a mechanic. They hooked it up to their diagnostic machine and determined that a wire controlling an injector wasn't working right. They said it was crimped or something and wasn't doing it what it was supposed to, so they replaced it and it seems fine now. I'll be driving to another state today so I'll be able to tell, but my wife drove it home and said it seemed fine to her. Only cost me $205, despite them having to rip up the engine to get to it.

sportyjudy, the rear plugs are fairly easy to replace. You have to rotate the engine slightly, which isn't as bad as it sounds. You put the car in neutral with the parking brake off (chock the wheels, though), then you unbolt the two engine struts at the front to allow the engine to move relative to the car body. Then you have a choice of using a long pry bar to put down the front left strut and tilt the engine forwards about 10 degrees, or what I did was hooked up a ratchet strap (the type used to tie down loads) to the engine hook near the alternator, and the other end in one of the holes at the front of the engine body and pulled it into the tilted position. Then, the rear plugs can be reached fairly easy, though you have to stretch and feel for them. As a novice it took me 3 hours to do the back ones. A mechanic should be able to do it in an hour, so they're charging you too much for the job. Rotating the engine sounds hard, but it's just not.