MP4.2+6.0

As a variant on the ad hoc tool if it helps: I have various Allen sockets that consist of the actual mm sized hex tip mounted in a fairly generic 3/8" square socket base. Usually Craftsman, though nothing unique there. I pull those tips out--some have a set screw and others use a circlip that locks into a groove. Then similar to this idea, I use a combo box/open end of the same mm sizing to turn the short hex Allen piece. How I have done various of the blind sensors on back of W12 heads up against the firewall.

Jack88

Problem solved, I just needed to retorque a couple bolts. Tight as a drum now. Now to handle the slight vibration I seem to have picked up. No misfires. Torque arm bolts not snug enough, maybe? Also, the car held its height with the front passenger on a paving stone, but after a couple hours with the tire off on a jackstand, trying to set it back on the tire had the front end bottom try to bottom out. That's a bit puzzling...

dvs_dave

Jack88

Yeah, just took some time to do! I did not forget to put it in jack mode, though. Before I parked it for all the work, I had signs of a slight suspension leak, I had both struts up front replaced with used units before the car was driven from Michigan to here in California. I had hoped the shop who did it just didn't tighten the fittings properly and thread tape would solve it, but I am doubting that to be the case. The part that confuses me is that it sat with the driver's front on jackstands and passenger front with the wheel on a cement block but it lost no height. After a couple hours with the wheel off while I removed the necessary pieces to access the needed bolts, putting the wheel on and setting it back down saw that it had lost all height.

Jack88

The car held its height overnight. Today, I finished getting it buttoned up and nothing leaks, no warning lights. Driving it does present a clunk over sharp bumps, so tomorrow morning I will take a look and recheck the bolts for the suspension and check the belly pan, since I had one side not secured to the wheel well. I don't feel anything from it, though. The vibration only seems present in neutral or park, with a sudden jump in severity at 1900rpm, and just perceptible at idle. I think it may have been there before my work and I didn't notice because it wasn't until after replacing the torque insulator that I was looking for it. At 1900rpm, it is readily apparent, but not severe. Almost feels like a misfire, but I have no codes. Anyway, at least I can drive it now. Still have to figure out why the back up camera and bluetooth died upon installing the XM module. Another day...

MP4.2+6.0

Just as a hunch for your vibration feel, if not in suspension or drivetrain, look at the intake manifold flaps switching system. Maybe your arms are disconnected or broken? Also, check and see if flaps actually move. Or, frozen? The springs are stiff, but the lever attached to the flaps shaft should move under some pressure. I recognize the slight vibration symptom from my C5 4.2 and its frozen manifold flaps; might also be sensed as sort of a flat spot in output.

Jack88

They worked when I checked them before, but it's easy enough to check them again. As long as the diaphragms suck in and there is no apparent outside damage, they're good, right?

MP4.2+6.0

No.. The shafts attached to the rods that then pass into the intake manifold guts have to move. Mine froze up. The seal design that those shafts pass through inside the manifold is subpar and they can corrode internally from water vapor and other crud from PCV system. At first I got them to move a bit, but they were binding. Just think of the shafts as like super long and kludgy versions of a carb or throttle body plate. It is being moved in one direction by more like a sketchy rope (the diaphragm set up) than a hard connection; the spring return is the other direction. Eventually one of the plastic rods at the diaphragms broke anyway, and at that point the shafts were completely locked up. If the rods got replaced with the metal aftermarket ones, another clue a prior owner had issues w/ the set up.

Jack88

Oh! How do I know if they are working? I checked them initially because I felt the car was down on power. I really would like to get it back up to spec.

MP4.2+6.0

You simply rotate them. Follow the plastic arms down from the diaphragms at front of motor between the cylinder heads. They arms snap on to an eccentric stubby metal fitting at the manifold end--just like a carburetor or throttle body linkage attachment. That is the place you need to rotate them. They rotate in the direction toward the plastic arms, since when the diaphrapms have vacuum applied, they get pulled in that direction. They are spring loaded on the return, so it takes some pressure. Alternately, if you had a vacuum pump tool, you could apply it at the hose connection of the diaphragms and watch the arms and then the linkage move if all is in order. Takes more vacuum though than we can probably muster just sucking on the hose by mouth. Test both sides of the manifold; they are essentially parallel independent systems that do the same thing.