...and it has its twitches.
On the first day of owning it I brought it from no-start to driving by replacing the in-line high-pressure fuel pump and battery. Upon a successful start of the engine, a few expected and unexpected twitches made themselves known.
The first and most obvious of which was that the engine computer had forgotten everything and was back in barely-running stupid-mode, but I know that will smooth out with some driving.
The second, and most worrisome to me, is that the speedometer was twitching all around.
When I first started the car, I had it up on jackstands because I had just replaced the fuel pump, so all 4 wheel were off the ground. I started it in neutral, and immediately the the speedometer started irregularly flopping between 0, 40, 60, and 90 MPH. I put it in gear, and it snapped to and stayed on the correct speed, for the most part. I took it off the stands and took it for a test drive, and the speedometer still twitched about when the car was in neutral and not moving, and driving around it only twitched twice, always to 40MPH, even at lower speeds and in Drive. Does anyone have any ideas why this might happen and/or how to fix it?
Next is the automatic transmission; is the shift into or between park, drive, and reverse clunky or should it be smooth?
Next is the radio; it's stock, unmodified, and the theft-deterrent lock has engaged, so it says "code" on the screen when I turn it on. Do I have to call or take it to a Volvo dealer to get the code, or is there another way I can find it?
After that is manuals for the car; if I can't get the one from the previous owner, who has the best manual for the car?
Last on my current list is the small upward-pointing orange arrow indicator light on the bottom of the gauge cluster, under the turbo gauge. What is it and why is it on all the time?
This car is totally new to me, and I'm totally new to working with unmodified cars from the 1990s, so any help or advice at all is very much appreciated. Thanks much in advance.

 

The orange arrow is overdrive, arrow means it's disengaged. The button on the side of the shifter should engage/disengage it.
Selecting a gear can be a little harsh on these cars, they aren't as refined as newer cars, but shouldn't be really harsh. Check transmission mount and centre bearing rubber support if really harsh.
Workshop manuals are available from a couple of publishers, I think the Haynes one is junk....
I would reset the ECU to get your car running better, simply disconnect battery overnight, the ECU's on these cars are very adaptive, self learning can take a full week of driving to render a really nicely running engine.
The speedo problem, do you have any ABS issues? If not, it's likely the instrument cluster, as the ABS system uses the speedo sensor and it's wiring to operate, so no fault in that system means it's upstream of that.
Ditch the stock radio, they're very average and good head units are so cheap these days...get yourself something with an MP3 jack and Bluetooth for your mobile phone for under $200 and you'll love it!

Regards, Andrew.

 

The speedo acting up is very normal-it may settle down some with driving but chances it is going bad and you'll need to rebuild it (diods changes)or get a used one. The radio is not great but if need the code it should be available from the Volvo dealer by the VIN number as long as it is the original Volvo radio that came with the car. Clunkiness is a relative thing, but as Typhoon says, check the driveline, probably something is worn out...