Was driving my 91 240 down the highway the other day and when I got back onto a city street I noticed the car was struggling to get up to speed. After about 4 stops and some messing around I made it home. I thought the issue was the IAC but after replacing it im still having issues. I can get the car up to about 40 mph but if I press the pedal down any harder the car will lose power. I have replaced the fuel filter, the air filter, the fuel pressure regulator and, again the IAC. Running out of ideas hoping someone can help.

 

Have you ever cleaned the throttle body?

 

Have you checked the transmission fluid? Amateur here, just found out my transmission fluid - no leak - was down 1.5 - 2 quarts. I hadn't checked it in years from what I recall. I lost acceleration, started slow, and was slipping gears. (Given this, I may have my mechanic do an ATF flush and new gasket.)

 

If you could test the fuel pressure that will be great. Sounds to me like one of the fuel pump/relay died. One in the tank, one under the car, try to use a paper clip to jump them without the car running, that way you can hear each of them and see if they both working.

 

If your car is running normally at constant speed on the highway it is probably getting enough fuel. Under acceleration as in city driving two things are required. Fuel enrichment above that required for constant running and ignition advance. Ignition advance occurs two ways, advance with RPM and vacuum advance for acceleration. You will need a timing light and the specifications to check it.

Your late model may have one or both these functions computer controlled. You will need the Volvo Green (shop) manual to know which and the specifications. Manuals are available for free download from ozvolvo/archive.

it is unlikely the IAC since it is disabled above idle.