Originally Posted by wbain5280

Given the age and mileage, I too would suspect vacuum leaks and the idle control valve. That valve is controlled by the small relay looking processor behind the false front on the passenger side in the middle.

You would do well to get the large rubber hoses that run under the fuel distributor, the hoses supplying air at the injectors, vacuum elbows and quite possibly the vacuum switches on the water channel at the front of the intale manifold. Also include the injector seals and holders and the rubber seals between the intake manifold halves.

The EGR pipe that runs from the valve to the intale manifold would also need to be cleaned.

You can tale the intake manifold off as well for a more complete cleaning. Take a lot of pictures and make a drawing of all the bolt locations and their length and positions.

While it sould like a large and complex job, it's really not that hard if you approach it step by step and document what you have done.

The only problem I had when I did my 420SEL was positioning the EGR pipe for removal and installation of the manifold.