95 Grand Am rough running, stall. Low oil pressure

i would say the low oil pressure is because of the car stalling and running at a lower rpm than normal and the oil pump is spinning slower. the rough running part could be something left unplugged (i would check the first because it is the cheapest). or something was not plugged in correctly or has a bad connection from sensor to the plug. sounds like a o2 sensor or something to do with emissions since you said the exhaust seemed thick. if you have a parts start around you they will usually run the codes on it for free and that could tell you whats going on.

the first mastake that u made was sitching from conventional to synthetic. with that many miles and that old of a car it will start beacking the engine down insted of lubeing it. and the reason that it dies when it is ideling is that there isnt enogh back presher. u need to replace the cataltic converter and go back to conventional oil. if it the smoke contines then u need to replace the piston rings.

conventional oil vs synthetic oil has NOTHING to do with his problems. only effect synthetic has on high mileage vehicles is gaskets swelling up or not creating leaks. dont make stuff up.

if the oil has nothing to do with it than what causes the smoking kaz thats what happend to my 97 GA with 205,000 miles

Oil typically has a tint of blue IF it's oil that's burning. I'd be more inclined to believe the shop screwed something up. And switching back to conventional isn't going to do anything because it wasn't synthetic oil that's causing te problems.

i change my own oil and i didnt screw anything up. and there was a blue tint but most people dont notice the blue tint.

In your situation it was just engine wear. Not because the oil was synthetic or conventional.

well i know that the car stalling at low rpms is coused by not enough back presher

synthetic oil doesnt burn... so it would not make smoke. the cat may be a problem because if it clogged then it would smoke and run bad. the low oil pressure im sure is caused by the low rpms of the engine. but you should hook a computer up to it and run the codes and see what you are getting. if the cat is clogged there would be too much back pressure and the engine cant breath.

the low oil pressure when it starts to stall is most likely that the engine is running much slower when its about to stall, therefore, the engine-driven oil pump is likewise turning more slowly, pumping less oil. at that mileage, there is a strong possibility the converter honeycomb is disintegrating, creating catalyst chunks lodging in the exhaust, creating excessive backpressure. with the car idling, park or neutral, rev the engine up a couple times, if the engine struggles to speed up, or rpm "bounces" up and down, there is most likely an exhaust obstruction. check that the fuel pressure is good also you should have around 35 psi with the key on/ engine off, check again at idle, then increase engine speed, if pressure starts to fall off rapidly, it will either be on obstruction in the fuel system or weak fuel pump. replace fuel filter first, then test again, if problem continues, it is most likely the fuel pump. as for the white smoke, make sure to determine if it is actually white or a bluish white, white smoke suggests there still may be a small coolant leak into one of the cylinders. bluish white smoke means its burning oil, considering the high mileage on this vehicle, synthetic oil may not be doing much good, as that oil is really meant for vehicles with very tight machining tolerances between moving parts. by now your engine has possibly worn considerable clearance between parts at this point