Have 1994 Chevrolet Caprice 5.7ltr (P vin). Failed emissions test due to idle miss. Car accellerates fine, little roughness when maintaining constant speeds. Have replaced injector/fuel rail o rings, fuel pressure regulator, plug wires, plugs, tuneup module, coil, decayed hoses, EGR solenoid. What else can it be? BuddyB Baltimore MD buddybeasley@verizon. Net.
Check to see if you have a vacuum leak, if you aren't reading 20" at idle you may have a leak or you could have a valve out or something inside the motor. It's best to take a compression check and if that's ok chekc your fuel pressure. You sold also scan your computer to see if there are any codes. You have to count the light flashes to get the codes on your car. Also if you are on the site here look undertop troubleshooting guides #2. After you get eht idleproblem fixed, change oil and filter, drive about 15 miles oneway if possible then have it tested. It should pass.