Re: 4gc woes

Posted by Owen_Dyneto On 2016/4/29 8:31:37

To set idle mixtures with a vacuum gauge:

Connect the vacuum gauge to read vacuum in the intake manifold, you can take it from the power brake fitting (but remove the check valve) or from the vacuum take-off for the wipers but before any junctions, but do not take it from the vacuum take-off for the distributor vacuum advance. Start the engine and allow it warm up and idle at a reasonably correct idle speed (450 rpm +/-). Select either idle mixture screw and begin to screw it in (clockwise, leaner mixture); the vacuum should begin to drop quickly and significantly. Then begin to richen the idle mixture by screwing it out slowly - the vacuum will begin to increase; stop when the vacuum ceases to increase and repeat the procedure with the other idle mixture and then go back and recheck the first one.

The optimum point you want to be it is with the leanest mixture (screws further in) consistent with the maximum vacuum. An engine in good internal condition and in good tune should give a very steady (no significant fluctuation of more than 1") vacuum reading of 18 to 20 inches of vacuum.

PS - you might want to check and make sure the ignition timing is correct before you do this.