I cleaned the throttle body, and replaced the throttle body gasket on
my 1988 Vovlo 740 GLE recently.  Lumpy idle was cured (car "hunts" for
an idle rpm).

If the throttle body gasket is bad, you might have idle problems,
because there is a vacuum present in the throttle body, and an
electronic switch monitoring the vacuum in order to regulate idle.  You
should be able to tell by looking at the gasket.  If there are voids or
tears, it is bad.  Price is only a few dollars, or you can cut your own
from gasket material available at most auto parts stores.

Its a good idea to do the gasket when you remove the throttle body,
since you are in there anyway...

oh.  BTW, symptoms are probably rough idle, with other possible
maladies.

Considering the age of your car I would also have a close look at the vacuum
hoses off the Throttle Body.  Best to make sure they are not leaking,
cracked, and fitting properly with correct tubing and all spring clamps in
place.  Maybe somebody has changed things over the years or worse yet hasn't
done anything at all.

I put my IAC  back on today and in the process noticed that one of the two
small vacuum hoses off the top of the throttle body was loose.  Not only
that, the spring clamps were missing.  It took the hose of and discovered
that it had been replaced, not original Volvo either.  Someone had put on a
piece of 3/16th inch.  Should really be 5/32nd or a bit smaller as the
3/16th was pretty sloppy on the nipple.  What looks good may not be quite as
it appears.

No question, my car seeks and finds idle quite nicely after cleaning IAC.
Still have rough idle on cold start so next step is this little ditty below
and if that doesn't work it's new distributor cap, rotor button, fuel filter
and wires (going for the Bougicord wires, sounds like they are worth the
money)

Poor Cold Idle: B230F/T ECU E-Prom Needs Update.  [Query]  My wife's 95 945T
(90k miles) starts fine on a cold (below 40F) start, but idles like crap for
20 to 30 seconds. If I hold my foot on the gas and keep it at 1500 rpm for 8
to 10 seconds, its fine. Car idles nicely when warm, and runs like a dream.
When I pull the plugs, they look great. I've replaced ECT and other parts
and cleaned the TB.  [Response: Abe Crombie]  Go to a dealer and have them
look at Volvo Service Bulletin 28-102 "modified e-prom for cold start with
low rvp fuel". This says the symptoms are: car starts and then immediately
dies and requires re-start. Runs rough for the first 45 seconds and may
hesitate on acceleration.  Recent EPA regulations have necessitated changes
in the formulations of gasolines (i.e. "oxygenated fuels"). The result of
these reformulations has been a decrease in the relative vapor pressures
(volatilities) of these fuels, which seems to be particularly problematic
for cold starts/idling.  The updated eprom chip to be installed in the ECU
is the fix to make it have correct fuel mixture computations for cold start.
You must have the number from your ECU in order to cross-reference the
correct eprom update kit P/N.  The change procedure described in 28-102
requires careful attention to static discharge.

I would think that most anybody would agree that an extra Throttle Body
gasket or two should be sandwiched in the old glove box in amongst the
insurance papers.

Remember, don't be spraying silicone around intake anywhere if you might
have leaks, goofs up the oxygen sensor. (and they are not cheap)

OK,
I found this on brickboard and it matches my issue. I am going to
replace the gasket today, remove and blast the knurled black idle knob,
then follow this example:

//Poor Idle; TB Cleaned; Now Idle is Too High.  [Query:] Well my
problem is certainly gone. It now idles at 1600 rpm, but that's a
steady 1600. Did I do something wrong, or was the crud in the throttle
body masking another problem? [Response: Evan]  Nope, the crud WAS the
problem. Crud makes the car idle lousy and slow.  Lazy mechanics simply
dial up the idle to mask the problem, rather than fixing it. You just
need to dial the idle back to spec.  On the end of the butterfly shaft,
the end where the spring is, there's a stamped metal plate. It has a
'leg' bent down that rests against the idle stop screw. The screw is
held in place with a lock nut. loosen the nut and adjust the screw.
[See Throttle Body and Throttle Position Switch Adjustment for more
detail on 89+ cars and Adjustment of Pre-89 TB, TPS and Base Idle: for
pre-89] Be careful, the screw head has a tendency to strip out.  In
retrospect, you should have taken a minute to make sure the screw was
free while the TB was on the bench.
Another thought: Before you do any of the above, make sure that the
'leg' on the stamped metal plate actually touches the stop screw at
idle. Some REALLY lazy mechanics just adjust the throttle cable length
at the big obvious pulley, rather than adjust the stop screw//

Problem Solved!

Thanks All!

1) Throttle body was dirty -- I cleaned it.
2) I reset the idle screw
3) I replaced the gasket
4) I removed and cleaned the IAC

Here's the kicker!

I installed the IAC with the arrow facing in the PROPER direction
(toward the intake). When the mechanic installed the engine, he had the
IAC backwards.

So, I have a nice idle at about 950rpms.  I tried to use the black
screw to come down to 750-850, but no luck.

Still better than 2000 and it sounds so much more relaxed.

Thanks!