94 dodge truck 1500 2w/d

You could have either a vacuum line leak or an intake gasket leak. Often an intake gasket leak will also cause an oil consumption issue as the actual vacuum leak is at the bottom side of the intake and will result in not ony a misfire at idle but will pull engine oil into the intake causing a loss of engine oil. The other primary sources of leaks I find are broken plastic vacuum lines, usually on the passenger or rear side of the engine. The throttle plates on these do cause a loud hissing noise [normal] so it's often hard to pinpoint an actual vacuum leak unless the air cleaner is on which mutes some of the normal air noise.

INCORRECT IDLE SPEED IDLE SPEED COULD BE LOW.OR YOU HAVE A PVC OR EGR VALVE LEAK.BAD PLUGS AND CLOGGED FUEL INJECTORS AND FUEL FILTER.