Title says most of it. If my car ('02 S60 non-turbo) is not under a load (only me in the car, not going up a hill, A/C not on, and not under 2500 RPM) then it does fine. If it is under any of the above conditions, it sputters & misfires. I replaced the plugs and coils this past week. I took it to Advance Auto to have them check for codes and they found none. The CEL is not on. It gets worse the longer I drive it.

I'm thinking either trash in fuel line/fuel filter bad, or upstream O2 sensor (downstream sensor replaced last year. Any way to be sure of either one? Any other options?

 

The most common failure that will do what you are describing is a failing coil pack. However, you've done that.

Misfires under load are typical of ignition failures. It sounds like you have a fuel delivery issue if the ignition is solid. The demand for fuel which it can't deliver causes a misfire. A scan tool that can read fuel trim data will be of help.

 

Here's what I've got:

Engine Torque: Hi 114.96 lb/ft Lo 14.3 Avg 48.13
Engine Power: Hi 53.75 HP Lo 3.01 HP Avg 13.69 HP
Mass Air Flow: Hi 3.45 lb/min Lo 0.3 Avg 1.1
Intake Manifold Abs Press: Hi 62.44 inHg lo 5.16 Avg 19.92
Short Term Fuel Trim % Bank 1: Hi 17.967% Lo -21.09% Avg -0.27%
Short Term Fuel Trim Bank 3: 0%
Long Term Fuel Trim Bank 1: Hi 8.59% Lo -1.56% Avg 2.15%
Long Term Fuel Trim Bank 3: 0%
Location of O2 Sensors Bank1: Sensor 1,Sensor 2, Bank 2: None: 3 3 3
O2 voltage(B1S1): Hi .84V Lo .26V Avg .51V
O2 voltage(B1S2): Hi .9V Lo .0V Avg .9V
Fuel System 1 Status: Closed-Loop, using oxygen sensor feedback to determine fuel mis
Fuel System 2 Status: Unknown

 

Check the coil wires that run in the split loom. The wires insulation can get very brittle causing the wires to become bare. Use liquid electrical tape as a cheap fix.

 

If you have a misfire condition, then there are probably pending codes in the system. It is really difficult to diagnose anything this random. What you are describing is a classic case of a weak coil or coils brought on by high combustion pressures from an open throttle blade.

Now I'm wondering what brand of coils you bought. A pic would be nice. If they are gray and black, they are probably the ones that we throw in the trash.

You can get codes read by a professional who can read Volvo codes.

 

See attached photo.

On the way back from work today, I dropped it into '4' instead of 'D'. The problems were still there, but much less pronounced. Don't know if that means anything.

 

I'm wondering if you have coil packs that have a spring on the spark plug end that can fall out. I've seen aftermarket coils that have a spring and then a small connector between the coil pack and the spring. The best design coil packs have the spring permanently attached to the underside of the coil.

 

Pulled on spring in pic. No movement.

 

Well - that ain't it. I'm out of ideas.

 

"On the way back from work today, I dropped it into '4' instead of 'D'. The problems were still there, but much less pronounced. Don't know if that means anything."

This plus the original post certainly sounds like a load-related problem that could, indeed, be fuel feed related. If the car were fitted with SUs or Webers, the steps would be obvious. In today's digital world, I don't know where to look beyond the fuel pump, filter or line. If the car has a fuel rail pressure sensor (my '09 V70 3.2 did) malfunctions like those should throw a code unless it is an injector problem. My '76 265 (V-R-P V6) would show similar behavior when the injectors (all too frequently) required cleaning. Does this engine use direct or port injection? My wife's 80's BMW was port injected and would also show signs of poor fuel feed when the intake valves got crudded up and disrupted the injection spray pattern.