Dave E.,
How did your spark plug replacement and major tune up go?
As a Tech Certified forum member, your feedback is useful to us less experienced S-Type owners contemplating similar maintenance on our vehicles.

 

I have not been able to get to it hope to do it tomorrow.

 

I finally got around to replacing the IMT o-rings, using the short route. Thanks to all for the guidance! Not a problem at all manipulating the valves out and back in.
I did find that all of the bolt anchoring the brace to the strut towers had been twisted off due to rust and replaced with new holes drilled and bolted. Then, in removing the bolt attaching the brace at the cowl, all three of those bolts were seized and they twisted off with surprisingly little effort. I am extremely disappointed with the quality of the hardware used in factory assembly. It will take an afternoon to drill out and tap all of those bolts, to be replaced with stainless hardware. . .. .:-(
But it starts immediately, no "check engine"light, no stutter as the engine heats up. Yay!

 

Hello again!
I finally got time to replace the intake manifold 0-rings using the "short route" technique. Seemed to run better after that, but then the same temporary stutter returned, with temporary amber "restricted performance" notice for about 10 seconds, then it stops and runs fine the rest of the day. Then the next morning, the same thing again. It seems to happen just as the engine reaches normal operating temperature. Is there a transition process at that point, either in the ignition programming or in the air intake system that might allow a lean or too-rich mixture?
Still a slight smell of hot oil when getting out of the car after driving.