Engine Mechanical problem
1995 Nissan Truck 6 cyl Two Wheel Drive Automatic 170000 miles

Hello. When I start the engine, it idles kind of 'rough'? I just replaced the spark plugs, air filter, fuel filter. Distributor cap and roter has been checked. Had the timing belt replace as well. The thing is; it only does it when cold. The only way I can describe the problem is like. 'there are 6 cylinders, all five fire and then the 6th is skipped???' because the whole car shakes a little bit, like a 'bump'. Once the engine is warm it doesn't do it. Oh and I do have a exhaust manifold leak.\.