I have a 1986 454 with a Rochester QJet 4bbl carb in a 35ft MH. I had a sticky throttle on hills when I floored the pedal for several mins. I also noticed the last 200 miles a slight back fire on initial acceleration. I installed the remanufactured QJet about 5 years ago and haven't had any problems. I decided to throw a rebuild kit on it since I had it off fixing the sticking secondary butterfly on the throttle plate gasket, due to the back fire. Simple, right? Couple new gaskets, new rubber on the accelerator pump, blow out some ports and a new needle and seat. I re-installed the QJet onto the motor and had to screw in the idle screw so much it's running from the primary curcuit and dripping in the venturies. I started at 2.5 turns out on the Idle-mixture screws and in or out nothing fixes the rough idle and black smoke out the exhaust. I have checked umpteen times for vacuum leaks and can't find any. Beside the sticky throttle on load and occasional bask fire it was running well. What could I have changed to effect the idle this way.
Wednesday, June 22nd, 2011 AT 8:05 AM