'98 v70 2.4l loss of power

Hey!
I have a 1998 volvo v70 with a 2.4L engine. For quite a long time, it
has had a noticeable loss of power nearly every time I drive it. On
occasion, it feels like the the power is normal, -- I think this
happens after a few days of relatively low humidity. Also, the gas
mileage is nowhere near as good as it used to be. It seems like having
the pedal down 1/4 of the way has the same effect as having it down 7/8
of the way. When the pedal is to the floor there is a noticeable
throbbing from the engine. When the preformance is poor (as usual) the
pedal needs to be to the floor in 2nd gear to accelerate onto a
highway. When the power feels normal I can achieve the same
acceleration with the pedal about 1/4 of the way down. Spark plugs were
replaced 12,000 miles ago along with the plug wires and (I think) the
cap and rotor. If I had to guess, I would say a weak distributor coil.
Mechanic says its possibly a plugged catalytic converter.
Thanks!

 

Sorry, I forgot to add that this has 140k miles on it.
Thanks

 

If there are no codes and the engine is not misfiring then the cat is
probably restricted. If that's true, then you need to find out why the
engine runs rich all the time, which is what probably killed the cat.

Bob

 

I would also err to a plugged exhaust. Sounds like the cat could have broken
up and the pieces are moving around sometimes blocking the exhaust.

Tim..

 

there are no codes and the engine doesn't misfire, but it does run a
tiny bit hot, which is why I suspected a rich mixture. This may be a
coincidence but our mechanic cleaned the injectors near the time this
happened. Since it runs nicely sometimes I didn't suspect the exhaust.
Is there some other way to check the catalytic converter without
removing it? Like the compression being abnormally high or something?
Also, how would I go about changing the mixture (if possible)?

ps: right around the time this whole thing started happening the check
engine light came on with a code PO404 or 440 (I think), meaning that
the air pump was malfunctioning. The code was cleared and it was
determined to be a computer glitch, though.

Thanks a lot!!

 

An engine running hot for no other apparent reason is also a sign of a
plugged exhaust system.

You may be able to remove the o2 sensor for a short time and road test it.

Tim..

 

thanks a lot!
I will try to remove the o2 sensor. Any ideas on why it would be
running rich?
thanks