Car won't idle after warmup

[Cade Carvell]

Hi,
  I have a semi-serious problem here.  For the last two weeks that car
once and a while after warmed up wouldn't idle well, it ideled really
low (500-600rpm) by the gauge in the passenger compartment.  When I
would try to take off it would sputter, then take off.  It wasn't all
the time, etc.
  Now, things have changed.  Starting yesterday, After the car is
warmed up, 15 minutes or so of running, the car idles low (500-600) but
it is steady, most of the time, once an while it will bounce 300 rpm's
for about 15 seconds.  When I go to hit the gas to bring the rpm's up to
a point when I can shift, etc, it won't accel well at all.  It takes
several revving sessions to get a reliable increase in RPM's (Above 2000
Rpm's).  Once I get the rpm to hit 1500, I will shift into gear no
problems, the power band is strong through the next stop, or slow down.
After that, it starts again.

  I did the ever so famous WD-40 hit on the vacuum lines about a week
ago, no noticeable change in rpm anywhere that I sprayed.  I pulled the
oil fill cap off will running, the monitor took a dip (100 rpm) after a
few seconds, it picked right back up.  Same thing with the dipstick
tube.  So I think that Vacuum is ok.
  The car always seemed slower then it should be when compared to a
friend of mines car, same year, everything, more miles though ;-).

  I am getting my propane tanks filled so I can heat up the garage to
work on it this weekend.  I went through the Bentley, really didn't see
anything that struck me.  There is no section on troubleshooting this
type of issue.  Does anyone have any idea were I should start, or what
the more common things that cause this?

Maintenance:
  New plugs, wires, engine sensors by previous owner.

Thanks a lot, I really need the help,


Cade Carvell
National Business Systems, Inc.
2919 West Service Road
Eagan, MN 55121
Office: 651-994-4400