The 740 has been having some wierd (possibly connected?) idle problems recently. It idles at 1600 RPMs, which is too high from what I've read. It shakes at idle and the idle fluctuates about 300 RPMs. Then when I actually put the car in reverse to back out of the driveway, the car will just die about 50% of the time. It is not being starved for fuel- it just cuts out as if someone has turned the car off. When it gets out on the road, the power is lacking until it gets to 2300 RPMs or so. Then it throws me back in the seat (all relative, of course- my DD is a diesel...). As a side note, the temperature gauge does not work, which I think is related to the cutting out at idle. I'm planning on:
-Adjusting the valves (is this even necessary? it helped the Mercedes when I did it)
-Replacing the temp. sender
-Cleaning the throttle body

Is there anything else I should do? I've done extensive work on my 300D, but never done anything on this car.

 

not sure about diesel, but sounds like intake air line leakage, perhaps vacuum leak too. check it out.

 

Where should I be looking for vacuum leaks? Are there any common culprits for something like that? I've got a MityVac for testing, so I'm OK there.

And this car is gas powered, my Mercedes is the daily driver diesel.

 

I imagine the Volvo you speak of is equipped with automatic transmission; check for vacuum leaks at the intake manifold where the vacuum lines are installed on the ports. they're all grouped in one general region atop the manifold...it should be obvious visually. check all lines from one port to the next. make sure all air-induction conduits are in nominal condidtion, and that they have not been compromised. the issue with variable idle may also be attributed to an idle switch out of adjustment, this can often be the case. after the throttle switch and of course throttle body/plate cleaning, check and clean the idle-air control motor and the coduits connected to them. next item is the Positive Crankcase Ventilation(PCV) box and lines. the PCV can become clogged and accumulate particles and viscious oils after many years, either clean or replace. be sure to replace, if replacing the PCV box, the flame trap and all lines/conduits which accompany the system. another item to check for is intake and/or exhaust manifold leakage. in regards to exhaust, check the condition of the catalytic converter. it may be clogged. or perhaps excessive exhuast leakage could negate backpressure, diminishing power.

I would be sure to check these items first, then move on. good luck.