Oldsmobile/Buick Repair: engine idle, torx screws, buick dealer

Question
I dont know if  the dealer used an iac ornot but   the last thing they wanted to do was change the computer.I already  had a new computerinstalled by my repair garage so i said no and took my car to my repair garage  there they  removed the new computer that they had installled and installed asecond new computer the car still will not idle.before i changed the blownhead gasket the car idled fine. I can't understand why the buick dealer could not solve this problem so far i'm stuck with a car i cqn not drive
      Bill Rhoat

Answer
hi bill.this eng has a iac mtr idle air control it is located onthe top of the engine mounted to the throttlebody or carb if you will.it will be a round part with a plug on it.it will more then likely be screwed into the throttle body or there will be two torx screws holding it on either way it will be the largest of sensors there.remove that and look at the bottomthere is a pintle that covers a hole in the bottom.is there carbon in that hole and can you pull the pintle freely.if so then clean part and reinstall.....next bill this eng has an egr valve on it.it is bolted right bye the thr body .there will be a tube comeing from the exhaust.and a plug right in the top and you will see 3 chambers with springs in them.with car running.if you can get it to stay running bye pushing the accelerator have a helper to take a hammer and tap at the base of the egr valve not hard enough to break it but enough toloosen up any restrictions inside.this is the two mostcommon things that cause erratic idle.   next ..this is very dangerous so bill be care ful.with eng running take brake clean or carb clean.carefully while not spraying on anything hot or plug wires.spray along intake manifold surfaces with car running at a steady speed.when you find a spot that causes the car to idle up.you have a vacum leak.repair the leaky gasket.also spray around thebase of the carb or tb.and look for the same thing.what the carb clean essentially does is seal the airleak temporarilly.hope this helps if not let me know    billymac