MG Car Repair: Idle problem, vacuum advance, intake leak
QuestionHoward thanks for your fast response, There are only two connections near the intake manifold. One goes to the PCV valve which screws into the top of the manifold and the other to the vacuum advance unit which attaches aft of the front carb and before the manifold. With both capped the rpm problem remains the same. The problem is only noticed stopped at idle, never when driving. I again tried the propane along the intake manifold, holding it longer at each spot I can reach from the top of the engine compartment, with no difference in the idle pattern. The hunting up/down is around 600rpm-800rpm from a given setting. Sometime that setting indicates 1000rpm sometines 1200rpm and sometimes 600rpm. when driving the car, the rpm setting the car selects seems to repeat stop after stop. At the low rpm setting I have to use the throttle cable to increase idle rpm. I bought a uni-syn to adjust idle,been using the hose method,but I am unable to get it to show a reading. Adjusting the center disk has no effect. With the eng speed around 1600 rpm there is no uni-syn indication from either carb. However using a vacuum cleaner and holding the uni-syn about 1/4" away from the hose end, gives a top of the scale needel indication. Is this related to the idle problem or just a operator problem?
Thanks Al
AnswerAl, I don't know what you are doing wrong with the uni-syn unit because if you run the center disk all the way in it will choke that carburetor off. Air has to be going into the carburetor or it wouldn't be running.
Tell me in detail exactly how you are using it.
With the engine running at idle and warmed up and the air filters off, slowly restrict the amount of air that can enter the carburetor. As you progressively restrict the air flow, if it at any time speeds up or smoothes out you simply have an intake leak or you have the mixture extremely LEAN.
Tell me also in detail how you set the mixture.
Howard
