86 mitz pickup. Rough idle. Rebuilt carb three times by three different machanics with no improvement. Is it being mis-diagnosed? Can there be a internal vacuum leak? Has new motor. Truck runs exellent on exceleration and high speed and power. But idle is rough with a surge. When you put your hand over the carburator the engine speeds up and smooths out.
I would be looking for a vacuum leak at the manifold gasket or a warped carby base plate, choking the carby with your hand is causing the car to draw air from the vacuum leak, I feel it will be a sizable leak and not t op hard to locate with a piece of hose used as a stethoscope.
September, 5, 2011 AT 11:32 PM
Hi there, I am working on my RV. I need to get it smoged but I can't fix the problem. The check engine light comes on after I drive it 20 mile +. I have check all hoses, 3 new o 2 sensors found leak out of head and exhaust manifold, Its got lots of air out of the air pump. It seems I hear a noise from one of the valves. When its hot after driving I hear a loud huming sound out of the front left side (facing the engine) from a valve or canister. When I start it cold I don't hear the second sound. The codes that came up after 20+ miles was Po411 and P1443 Need help, thank you Robert