what could be wrong with my 1999 buick century?

great wording... >You may have a bad IAC ( idle air control) but try eliminating any vacuum leaks and cleaning the throttle body first. Remove the intake snorkel, have someone hold the throttle wide open for you and scrub the back side of the throttle plate and surrounding bore with an old tooth brush and some carb cleaner. Be sure to spray some into the small holes next to the throttle plate. That should help stabilize the idle. If it still has a problem, replace the IAC.

IAC had popped in my head soon after I posted the question. thanks, Ill give it a shot. this is my old beat up commute car so im trying to solve this as cheaply as possible. Im going to see if its the same IAC valve from 97 to 99 and swap them out. the shop I took it to said they cleaned the throttle body and the MAF and new air filter (just as a guess because the car wasn't acting up for them) ...ill clean it up a little more myself. thanks for the suggestion.

yep, hard to fix something when its not acting up..

well.. cleaned everything up (it wasn't too bad to begin with) and swapped my AIC out with the one from the 97 (which runs fine) and no change.. so that wasn't it... another thing eliminated I guess. but need more suggestions.

have you tried to spray everything for a vacuum leak?

Check ( ETCS ) Electronic Throttle Control System - fuse. Just recently had a vehicle with the same problem replaced fuse runs great.

I have not.. honestly im a bit nervous to do that haha.. you are referring to the carb cleaner trick? I think im going to swap out EGR valves in a bit n see what that does. SO MANY things have the same symptoms im losing my miiiiind hahah

ill check it out firebird! thanks for the idea....im running fresh out of em.

This is a fuse that is in your fuse box most likely the one under the hood on one of the wheel wells.

you can spray the egr while running with carb spray and see if the rpm changes also...

couldn't find a fuse with the label you described.. I looked in the fuse box under the hood aswell as the fuses in the side of the dash. nothing similar to what youre describing. also swapped EGR valves.... no change... hard start - runs extremely rough and dies. the fact that it DOESNT die when I unplug the MAF sensor has to mean something right? it still runs like crap but wont cut off on its own like when its plugged in.

Swap the computer and coil packs could be a spark quality and crappy pc issue

So what fixed it? Did you find out what was causing your hard start, runs rough?

I recently had transmission work done on a 2005 buick century, when I took it to the shop it was running fine but when I got it back it starts stalling, and the security light came on it cranks up and I can drive it, but it would stall do I have to reset my security system?

I would check your crankshaft position sensor, $23 @ Autozone. It takes like 10 minutes to swap it out. Disconnect negative battery cable. You'll need a deep socket 10mm socket (it's a 10mm stud bolt you'll be feeling for). You'll be working blind. Reach under and in back of the alternator,and feel around, you'll quickly hit pay dirt. Disconnect the electric, undo the stud bolt, remove the sensor. Replace the sensor, make sure it's fully seated, and line up the bolt hole. Replace the stud bolt, and hook the electric connector. Reconnect the negative battery cable. If it still runs rough, it may be either the crankshaft position sensor behind the harmonic balancer, or the ignition control module.