Pontiac Repair: difficult starting cold, throttle position sensor, intake manifold gasket

Question
I have a 95 Grand Prix 3.4L DOHC.  When trying to start cold revs to ~4000 then stalls, several attempts later will idle very rough and prone to stalling.  After reaching temp, no prob.

Answer
Hey Robert:

2 possible causes. #1 a/c pressure transducer/switch on the high side pressure line. When the car is cranking the sensors have a tendency to short out and cause the throttle position sensor supply voltage to drop and then it induces a throttle angle into the ecm's data. Usually when this happens if you have a scan tool and it acts up you will se anywhere between 2-4% throttle angle with your foot off the gas. No liely in the older models but I have sseen it a lot in the 92?-94 years. Possibility #2 and more likely is a leaking lower intake manifold gasket. with the engine warm not hot take the plastic engine cover off on top of the injectors and spray some car cleaner around the lower intake manifold if the engine stubles or stalls or the idle picks up you found the problem. that gasket needs to be replaced. Do not do it hot because when it warms up the parts swell up and seals off the vacuum leak. Also for a FYI if this engine has over 60,000 miles and you haven't changed the timing belt do it!!!!!!!!
Good luck and happy holidays :)