Pontiac Repair: 1991 pontiac grand prix se, coolant temp, manifold gaskets

Question
THIS CAR HAS A 6CYL 3.4 LITER TWIN DUAL CAM IN IT AND WHEN IT IS COLD OUT IT WILL NOT START IT CRANKS AND BACKFIRES AND WILL NOT START. NOW WHEN THE TEMPERATURE GETS UP TO 40 DEGREES OR MORE OUTSIDE IT WILL START UP WITH NO PROBLEM I HAVEN'T A CLUE WHY THIS IS HAPPENING CAN YOU HELP AND IT IS GETTING FUEL WHEN ITS COLD OUT I KNOW THIS FOR SURE.

Answer
Hi Randy:

Well it can be a bunch of things. Your going to need a scan tool to see if there are any codes in the system first off. Without that You out of luck and will not have a directionto go in. I would look to see if the coolant temp sensor is reading correctly when the engine is cold compait the engine and air intake sesnors they should be with in a few degress of each other. I would check fuel pressure when it's cold. I belive that engine has about 40-45 PSI. When this does start up does the enegine rpm's race up high? If so that would indictae a vacuum leak. A likely cause would be the lower intake manifold gaskets are bad and when it's warm out or the engine warms up it seals the leak up and it runs okay. You try doing this take the lack engine placti cover off the engine and with the engine runn when it's cold spary some carb cleaner around the injector area if the engine rpm's increase or the idle stumbles you found the source of the vacuum leak. That is where I would start looking. Good Luck :)