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Stalling when I let up on gas pedal

I’ve got a 1994 BUICK PARK AVENUE V6-3800 3.8L, and it’s stalling on me pretty frequently. The car seems to idle and accelerate fine. However, if I use the gas pedal, then once I take my foot off the pedal, the engine stalls. If I let it up slowly and carefully, or if I’m just driving slower, sometimes it won’t stall, but the rpms will drop low and the lights will dim for a second before they go back up.

I’ve checked my PCV valve, replaced my spark plugs, and used some wire dryer, fuel line cleaner and gasline antifreeze.

At this point I took it to a mechanic. They cleaned the throttle body and mass air flow sensor. Didn’t help, so I brought it back. They replaced the IAC motor. Still didn’t do anything.

Any suggestions on what the problem could be and how I could check/fix it myself if possible? Thanks.

I think at this point what I’d do if it came in the shop would to do what you could do at home… Check the maintenance record and see when the spark plug wires and fuel filter were last replaced. If they haven’t been replaced lately, change them. I’d suggest getting a $3.00 can of carb cleaner and clean the throttle body yourself… just take off the large hose coming from the air filter to the intake, open the butter fly valve and spray some cleaner inside…allow it to set a few minutes, and spray some more while visually noticing how dirty it is.
Take off the EGR valve and clean it with the carb cleaner making sure the
piston is not caking up with carbon. These steps will only cost you a couple of tune up items and a can of carb cleaner.
Maybe some one with another late model 3800 motor can give more advice.
Good luck.