what could be wrong with my 1999 buick century?


Asked by Jul 11, 2015 at 05:09 PM about the 1999 Buick Century Custom

Question type: Maintenance & Repair

GM 3.1l engine 200k + miles.

it was hesitating intermittently about once a month for a while then recently started to develop a rough idle every few days then itd go away and run correctly.  eventually stalled out twice while driving.. took it to a shop twice...no answers.

sounded like a timing issue.... loose or slipping timing chain so i replaced it (i discovered the old one WAS scraping the cover)... but that didn't solve the problem.

now when i start the car (hard start) it runs EXTREMELY rough... jumping around.. rocking back and forth.. intermittently ticking and knocking...it lasts about 5seconds then dies and stalls out..
suspecting the Mass Airflow sensor i unplugged it and started the car... the car still runs like garbage..but will not die...it will continue to run like garbage until i turn it off myself.

i just happened to have a 1997 buick with the same sensor so i swapped them out to see if it ran better with a new (used) sensor.... no change though.
so now im running out of ideas.

replaced fuel filter, all plugs and wires, checked fuel pressure regulator. Fuel pressure at the rail is 41psi with key on which is within spec.

(it is unable to move at this time...starts - runs like garbage - dies (unless i unplug MAF)
check engine light is on and oil light is on aswell when the car is running.

thanks for reading!

11 Answers

Kelly Mayo

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.

Kelly Mayo

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.

Kelly Mayo

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.

Kelly Mayo

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.

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