My Volvo seems to be running pretty good but the idle is erratic & i have no power. I did notice that if the engine is cold & i take off it has even less power. Could it be the coolant temp sensor? I'm stumped!

 

Not. enough. info.
What kind of loss of power, does it stumble, miss, or do you have it to the floor and it just takes off nice and smooth, but slowly. Does it idle bad all the time? Could be fuel related, vacuum leaks, something is clogged, old fluids... Some more info would help, when did this start, what have you done on the car, what have you not done...

 

a 1990 740 should have the OBD code display under the hood... See Engine and OBD Diagnostic Codes ... you are interested in the codes in the "A" box (some cars have a "B" box for accessories), in pin positions 2 (fuel injection) and 6 (ignition). Many codes don't throw the 'check engine light' on these cars, but still help you diagnose problems.

whole PILE of useful troubleshooting tips here specific to these cars, Engine Tune and Performance:

 

Thanks guys! It runs smooth down the road but has no power. It doesn't stumble or miss when giving it gas, it just has no power. Where is the box to check the codes & how do you do it? Can someone take a picture of the box under the hood?

Thanks,
Scott

 

its a little black box just forward of the left wheel well, has a cover on it, you lift the cover, and there's a jumper thats stored plugged into the cover, so unplug it from the cover, then insert it into position #2 (are sockets 1-6 and it should say "A" on it, and have a button and a LED). turn the ignition to position II (on but not started), then press that button for > 1 and < 3 seconds, and release and wait. the code comes out quite slowly. 1 blink. pause. 1 blink. pause, 1 blink. is code 1-1-1, which is no error. if you get a code, press the button again for about 2 seconds (>1 and <3), and get another code, when the first code repeats, thats all she wrote. key off, move jumper to #6, and key on and do it again.

see the URL I pasted above for the meanings of the codes.

 

the front of the car is to the left in those pix. On my 92 740T, this is between the EGR Vacuum modulator (california only), the wheel well, and the power steering reservoir. If your car has cruise control and/or climate control and/or some other stuff I can't remember, you may have TWO of these little boxes, the other one is labeled "B" and has nothing to do with the engine.

 

I always forget about checking the codes because I have never had any codes come up with erratic idling and loss of power and stumbling on acceleration, so I'm thinking you will not have any...

 

Thank you so much guys!! I hope i can do this & not mess up the readings! lol