1999 mazda 626 2.0L 4cyl engine shakes horribly in idle in drive. have to put car in neutral when at traffic light..... changed spark plugs wires valve cover gasket (it was leaking), air filter, changed oil.... still shakes, not quite as bad, but still shakes... HELP!!

 

Possibly vacuum leak is causing shake check intake manifold gasket,check hoses,it may be a hose disconnected

 

what colour were the plugs you took out?

Are you using oil or fluids?

Does it run OK when moving?

When was it last services and was the fuel filter changed?

 

egr valve probably

 

looks like it is an engine misfiring problem. the probable causes of misfiring are damaged distributor cap, spark plug, or a burnt out valve.