Took my daughter's beloved V40 to Costco to rotate the tires while the car was home for Christmas, and along the way floored it on a freeway entrance ramp just to see if all was well. Alas, it stuttered, sputtered, and hesitated abysmally.

Got a misfire on cylinder 2 code, so I replaced that coil when I replaced the Champion RC8PYp4 plugs that had 24k on them. Retested, but still the hesitation under hard acceleration, especially from 50 or 60 mph. This time I got a misfire on #3 code. The new coil serves plugs 2 and 3, so I took it to the shop.

They spent all day testing, replacing plugs (with NGK) wires, coils, but kept getting new diagnostic trouble codes that pointed to Mass Air Sensor, Manifold Pressure Sensor, Fuel Pressure Regulator, but none of those parts were indicated consistently. They took the new stuff off, cursed, and gave me the car back for free--partially because my daughter is leaving tomorrow to drive 2 days back to her home. The car does fine under normal driving and gets 28-32 mpg on long hiway trips. (That's the good news.)

So, what to do next? Vacuum leaks? Fuel pump or regulator or filter (which I've been meaning to replace)?

Thanks in advance.
Michael

Just a hunch, Look carefully for a leaking or torn air hose after the mass air sensor to the throttle body. I've had one SOB tear underneath where it needed to
come off to find it.

Also you might carefully search for a vac leak. One way I'll try next is to use
a little propane (Unlit) and see if the engine revs increase when idling when you touch suspect areas with the propane gas. Some people have used small/ tiny zips
of starter fluid around vacuum trees etc, of course both ways are very dangerous if you are too heavy and/or fast with this treatment. Maybe others will offer
less dicey methods, be careful.

If the vacuum lines look crappy, another tack might be proactive and change them all. It might be a bright idea for the 100,000- 200K mile tune-up.... pick a number. Rubber goes west with time.

Air and vac leaks can raise you-know-what with oddball codes and erratic behavior.

Good luck, Bill

I've had issues like that with our '01 on and off.

In my experience...
Pull the coils again and inspect them under a magnifying glass. You may see some burn marks or cracks. FWIW, we were getting a misfire code for cylinder 3, but it turned out to be a crack on the coil housing for cylinder 4.

Others swear that the S/V40 engines are sensitive to spark plug type. They say to only use "Volvo" branded plugs. Obviously Volvo doesn't make spark plugs, but it is very hard to figure out just what plug is the equal. I'm still not sure I agree, but did replace ours with "Volvo" plugs.

Vacuum leaks? I've tried to chase those down too, but never found any.

Don't feel too bad. The codes your getting are pretty common in my experience with our '01. I've had those many times and the MAF, MAP or FPR have yet to be the problem. Not saying it couldn't be, just that it never was for me.
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"Differences of opinions should be tolerated, but not if they're too different' - Sharon Craig