DO THE BLEND DOORS IN THE DASH MOVE WHEN COMMANDED? IN OTHER WORDS, ASSUMING THE A/C WORKS BECAUSE OTHERWISE YOU MIGHT NOT BE ABLE TO ANSWER THE QUESTION, IF YOU DECIDE TO CHANGE THE POSITION OF THE FAN i.e. VENT TO DEFROST OR FLOOR TO FACE, DOES IT DO WHAT IT'S SUPPOSED TO DO? THE REASON I ASK IS THAT THOSE DOORS ARE MOVED BY ACTUATORS MOUNTED UNDER THE DASH THAT OPERATE ON ENGINE VACUUM. WHAT I THINK YOU HAVE IS A VACUUM LEAK. AND THIS IS NO SMALL LEAK! IF THE LEAK WAS VERY SMALL, THE VENT PROBLEM PROBABLY WOULDN'T SHOW ITSELF. ONE OF THE EASIER WAYS TO CHECK IS TO FIND A PIECE OF SMALL DIAMETER HOSE LIKR 1/4 INCH TO 3/16 INCH INSIDE DIAMETER OR SO (YOU MAY FIND SOMETHING LIKE THAT AT A HARDWARE STORE OR YOU MAY BE ABLE TO USE SOME VACUUM HOSE FROM AN AUTO PARTS STORE.) ALSO GET A SMALL FUNNEL THAT WILL ATTACH TO THE END OF THE HOSE. ONCE ASSEMBLED, YOU CAN USE IT TO FIND THE LEAK. WARM UP THE ENGINE SO IT WILL IDLE THEN SIMPLY HOLD THE FUNNEL TOO YOUR EAR AND PROBE AROUND THE TOP OF THE ENGINE WITH THE OTHER END., BEING CAREFUL TO AVOID THE FAN AND BELTS, AND LISTEN FOR A HISSING SOUND. ANOTHER WAY TO FIND A LARGE VACUUM LEAK IS TO TAKE A COMMON SPRAY BOTTLE, PUT SOME WATER IN IT, SET THE SPRAY FOR DISTANCE AND USE THE WATER AS A PROBE--IF YOU FIND THE LEAK, IT WILL TAKE THE WATER INTO THE INTAKE AND YOUR IDLE SPEED SHOULD SLOW DOWN FOR A MOMENT. BUT BEFORE YOU DO ANY OF THAT, OPEN THE HOOD WITH THE ENGINE OFF AND TAKE A GOOD LOOK AT THE LARGE BLACK RUBBER HOSE THAT RUNS BETWEEN THE AIR CLEANER AND THE ENGINE. THIS IS THE INTAKE HOSE AND IT SHOULD HAVE FOLDS OR RIDGES IN IT TO HELP IT BEND. KIND OF LIKE AN ACCORDION I GUESS. THIS TYPE OF HOSE IS PRONE TO CRACKING, USUALLY AT THE BOTTOM OF THE FOLD OR ON THE VALLEY AS OPPOSED TO THE PEAK. GET A FLASHLIGHT AND TAKE A REALLY GOOD LOOK ALONG THE ENTIRE HOSE. THE OTHER QUICK THING IS TO LOOK FOR A HOSE THAT IS ABOUT 1/2" TO 3/4" IN DIAMETER RUNNING THE VALVE COVER TO THE INTAKE MANIFOLD AND MAKE SURE IT ISN'T DISCONNECTED OR BROKEN.
