Bad Temp/Oil sensors?

[Brooks Ellis <brooks@alpha.pr1.k12.co.us>]

   I have a 1990 100 Q 5spd /2.3l I5..blah blah anyway..
   I have had a problem twice in the last couple of weeks or so. The 
first time, I was driving along the highway, doing about 40 behind some 
guy towing a trailer = I passed him in 4th and got up to about 80/85ish. 
Then about 4 seconds later while I'm decelerating ( just foot off 
gas...hey, that section has a lot of speedtraps, and if I only do 10-15 
over they wont bust me...anyway), the oil light ( on the auto-check 
system ) went on, and it started beeping at me. I pulled over about a 
quarter mile down the road, as there was no place to stop right away. I 
let it sit for a while, and checked the oil. The oil level was OK, and I 
didn't feel like calling anyone to pick me up and screw with it later, so 
I started it, and drove home 8 miles away. The car was fine for the next 
week or two, including daily commutes of 50 miles and a couple 200 mile 
trips. Oddly enough, this evening, as I was driving home, It did the same 
thing again. This time I was driving on the road up to my house, which is 
very bumpy (dirt road..I am getting good training for rally racing!), I 
was just speeding up a hill in 3rd, and it did it again. I stopped right 
away, I noticed the analog dial-gauge was reading about 1.5 bar oil 
pressure, and I got out and checked the oil level. It was fine, so I 
started it up again, and drove home. As I started it, the pressure was 
hovering about 1.6 to 2.0 bars pressure, but as I got going it leveled 
out about 1.9-2.0. 

It seems that the pressure has been low for a while - It stays about 1.8 
to 2.2 the whole time...Sometimes when I do a cold start, it gets to 2+ bar.

I have also noticed a different problem in the last couple of weeks with 
my engine (coolant?) temperature gauge. Every so often it reads 0.. or 
less than 0. It will do this on cold starts, or if I have had it running 
for two hours - doesn't really matter. My engine has also been running 
somewhat hot recently - If I sit at a light for 30 seconds plus, my 
radiator fan will probably kick on...then it takes a long time to cool down.

  <whew!>

Basically, what I am interesed in, is: 
1. could the two gauge problems be related - a bad ground? I had a local 
stereo shop install some stuff - could they have screwed something up?

2. is(are) the sensor(s) bad?

3. could my oil pump be going out? how about the coolant pump?

4. a leak perhaps? 

5. i have already runined the engine by driving it after the light came 
on, so it doesn't matter anyway, and I should go drive around town in 
second until the whole thing just blows?

6. somethingelsegoodorbad?

Sorry for the long post, but I do treasure my poor car. I find the idea 
of walking or riding a bike fairly disagreable, so I must keep my car in 
working order.

lates & thanks & all that

telmeyoursecretsiwanttogotohelifihadashotgunidblowmyselftoheldienowlivelater
bo    brooks@alpha.pr1.k12.co.us            Brooks Ellis                  de
againitaughtthekillinggamefirstiwontgiveupitwantsmedeadandgoddamnthisnoisein