I have replaced my spark plugs with Volvo plugs. I have replaced my injectors, and fuel injector regulator, coils and wires, and this car acts like it doesn't have enough fuel to push the car until it reaches exactly 2k rpm. I am getting a code PO300 which I know if muti miss fire, but I can't figure this one out. It runs great once it reaches and maintains 2,000, but if it drops below that, the car has a fit. I can sit in park and slowly rev the engine, and it struggles between 1,500 and 2,000, but once it does, it runs great.

 

You gap the plugs correctly? You smell gas on the engine, or in the catalytic converter area? I just resolved my P0300 misfire code on my 2000 S40 with new plugs. Test your coils and wires with a multitester to make sue the signal (current) is getting to the spark plugs correctly from the coils and wires. It does sound like you definately have an ignition system problem. You could also test the fuel pressure by using a cheap pressure testing tool, to make sure that there is enough fuel getting to the injectors from the fuel rail.

 

I did check the gap in the plugs, and they were within range. I have already changed the coils and injectors. I don't smell raw fuel under the hood, or at the exhaust. It is acting like it isn't getting enough fuel. How much pressure should I have in the fuel rail? Do I just go to an autoparts store and tell them I need a universal gauge?

 

Harbor Freight has the cheapest fuel pressure tester I've run across to date, about $15. The chain store auto parts store has them for over $60. Both seem to be cheap Chinese made testers. Your money, your call.

Is this lack of power below 2k rpm a new problem?

Have you cleared the P0300 code after you replaced all the parts and it came back?

Could this be a boost issue? There is an electric actuator for the wastegate to control boost. It should set a code though if commanded boost does not equal actual boost.

 

You check the fuel pressure regulator? See if it has gas coming out of the vacuum tube that feeds it from the bottom. If there is fuel in that tube, the regulator is bad and the fuel pressure will be wrong. Mine went bad some years ago in my 2000 S40 and it took forever for the car to fire up (long cranking), and it created a stutter in the combustion cycle and threw a code. New regulator took 30 minutes to install, all good after that.

 

How hard was it to replace your fuel injectors? Can you write out steps?

 

It's really simple to remove and replace the injectors. I'd highly recommend new O-rings when you put them back in (assuming removal to clean them). From memory:
1. remove underhood fuel pump fuse and run car til it dies (relieves fuel pressure)
2. remove plastic beauty cover over fuel rail
3. remove plastic cap on shrader valve and relieve any pressure remaining in rail
4. disconnect fuel line
5. disconnect vacuum hose to FPR
6. disconnect injector electrical connectors
7. remove 2 bolts holding rail to intake
8. gently and carefully pry rail with injectors from intake. This may bend the thin aluminum retaining piece if the injectors stay with the intake. You can easily hammer it flat again. Gently and carefully are the keys here. Work the injectors loose. Don't just use a crowbar unless you want to replace the fuel rail too.

EDIT: Safety always. Cover your eyes when relieving fuel pressure. Have a fire extinguisher ready. You are working with fuel.