Your mechanic had to remove the intake ducting to change the spark plugs. He may have left a tube unconnected. Or dislodged the one I speak of below.


Did he clean the EGR valve and the EGR tube that goes into the back of the intake manifold. EGR sets code 400. Mine was coked totally shut at the end of tube. Rough engine idle is a symptom.

Also, there is a a rubber vacuum distributor block which plugs into the intake manifold at the rear of the engine. This block has a Pitot tube which sends a signal to the Manifold Air Pressure (MAP). Mine had lost it's resiliency and crumbled when I removed it. The engine will run very rough if this block is not intact and properly inserted.

Good luck

Jim in Phoenix