I OWN A 2000 S40 AND I AM HAVING A PROBLEM WITH THE TACHOMETER WHICH IS RACING WITHOUT STEPPING FOOT ON THE ACCELERATOR . THE VEHICLE IS NOW HAVING TROUBLE STARTING ALSO.

It,s either not getting enough gas or not enough air. Check has and air filters.

I'll answer for A/T auto tranny car, with 4wd.
RPM.

got a dash tachometer?
if yes this is easy.
you step on the throttle (right foot) and advance the RPM
to where.
stuck at 800? rpm
goes to 1500 to 2000 and shakes, (brakes iced up. and frozen)
goes to 3000 rpm or more, (tranny failure) or 4wd in neutral?

low power to what, wheels or electrics? (dim dash/head lamps?)
if wheels,
is this true in all gears.?
is car A/T ? auto tranny?, is car 4wd or AWD, or what? options
are you in 2WD, (two wheel drive?)

if the engine has low power in any A/T cas?
FSM steps. (under A/T on car diagnosis) yes, RTM.

we do the stall test. (point car in safe direction, dig?)
we set brakes hard (and and foot)
we select DRIVE (or 1s to REV, i do all 3,one by one. )
we then race motor with right foot for 5 seconds max.
we look at the tachometer, it will be like 2000 RPM (stop now)
is it like 1000 RPM then the engine is weak
if much over 2000 rpm the tranny is slipping and is not a weak engine
these numbers are generic, the FSM covers this. read it. RTM
read the manual or get help. there are only 2 ways.

if all this is alien to you, then take it in
any ASE shop can do this.

Yeah, the Volvo dealer that you are dealing with is the proverbial POS - if possible cancel the deal, get your dinero back and get the car from an outfit that can properly service the vehicle.

Hi Eveerei, If you're asking about the tachometer and not the speedo meter, that meter records the engine RPM speed and not the vehicle ground speed The tachometer at idle (when you stop at a traffic light, stop street or any other stop) should record an engine speed of about seven hundred to seven fifty revolutions per minute, at idle. It will increase in relationship to how hard you push your foot on the accelerator pedal. Hope this info helps you. Happy new year and regards John

The engine does not need to be raced when cold

The vehicles computer will adjust the idle according
to how the manufacture programmed it

After about one mine or so, the idle on most vehicles
comes down to approx 750RPM, generically speaking

When you put the car in gear,assuming it is an automatic,
the rpm will drop a 100 at most & may be adjusted by the
computer, just as it does when you put the A/C on. That is
to compensate for the change in engine load

You should be waiting for the rpm to come down to 650 to
800 & then a couple more minutes for some temp to come
up, before driving off. In cold weather wait at least 5 min or more

I think your vehicle is not working correctly, or you not explaining
it in a way I understand what answer you want

i had a 2001 aurora with the same exact problem. lucky for me a drunk driver smashed into it with a plow truck and it tumbled down a cliff into a river while it was parked and they gave me 12k for the car that i paid 8900 for .
i beilive its and ignition problem

Maybe the throttle position sensor? Its attatched to the throttle body or wherever the throttle is attatched to the intake system.

your fuel injectors are clogged

This is a common problem of Volvo S40. You can try this trick to turn off the flashing arrow light.

1) Turn off Engine
2) Turn key to "On" position (Not start the engine), you will see the panel light will on
3) Step on the break paddle
4) Shift the gear from "P" to "L" 10 times
5) Turn key to " Off" position
6) Now you can start the engine.
7) If doesn't work, you can repeat the procedure.

Hope this tick help
Good luck