240 occasionally loses power

[tog244]

My 244 will randomly lose power and the exhaust note changes. foot to the floor in second or third and it will struggle to go past 40. when this happens it usually fixes itself in a minute at most and then its fine. I found this thread (linked below) and was relieved and so I found said fuse (spade fuse under the hood), saw that there was some oil and other grime in the connecters so I took it apart and cleaned everything, put a new 25 amp fuse in and mounted the thing that held the fuse better than it was, and went for a drive. lo and behold i still had the problem. now it wasn't as bad- not as much of a power cut and for less time typically- but still definitely noticeable. I got home and checked the fuse and it was bone dry, as were the connectors. any suggestions? (no fuses in the cabin were blown either). My initial thought was a sticky throttle body that wouldn't open up all the way sometimes so i removed that and the idle air control valve and cleaned them both but the problem was still there. my pcv system is clogged up but i ordered a new breather box and flame trap to get here soon. figured i would mention that just in case it helps



https://volvoforums.com/forum/volvo-...eration-19401/

[283SD]

The pipe from the air cleaner to the TB might have a hole in it, loose clamps on the pipe, clogged fuel filter?

[kampman]

The exhaust note changing makes me think failed cat.

[esmth]

my guess is spark plug wires occasionally shorting on something. (valve cover or fuel rail/injector clips?)

[tog244]

Ill check the air filter to TB pipe although nothing stood out to me immediately

would a failed cat cause the random power loss? im hopeful that its more of a fuel delivery issue that makes me run lean which causes the exhaust to sound different- this is a complete guess tho

I would be surprised if it was spark plug wires as i replaced them and the plugs in the last 6 months but that and the distributor is a good easy place to check right off the bat

[283SD]

I the cat matrix comes loose it can plug the pipe, had it happened to our '90 wagon.

[tog244]

was there a reason for the cat matrix loosening? i think ive heard clogged air filter and or fuel filter can cause it- plus ive had some unburnt fuel coming out of my exhaust so i would guess youre correct in the cat being messed up

i think the logical next step is to remove the exhaust and cat and go drive around for a while. y'know, for science

[dl242gt]

I'd suggest checking the condition of the fuel pump relay. Change your fuel filter. Then if it's still happening. I'd suspect the fuel pump is becoming intermittent. It may be because the wiring has decayed under the car.

[tog244]

well i highly recommend unbolting your exhaust from the downpipe back, if you have a few hours to spend struggling with rusty bolts and wrestling the exhaust pipe out from your rear axle and especially if you want to feel like a menace to society on a test drive with how loud you are.

i didn't have any of my acceleration problems with the open downpipe although it wasn't a long drive so thats somewhat inconclusive, however, there absolutely was something rattling around in my cat when i removed it, im not familiar with the insides of a cat but i assume it what 283sd called the matrix

so now to try to prevent my future cat from blowing out this same way, ive heard replace the fuel pump(s), fuel filter, air filter, MAFS, fuel pump wiring, clean injectors- all sorts of stuff. Is there any way to narrow this down or should i just start replacing the least expensive things first and cross my fingers i fix it early on?

Ive had a few problems with timing in the recent past tho so maybe thats what caused the start of the blowout and now im good? I have no clue

[ermit71]

Fuel pump relay?

[tog244]

good idea, is there any way to tell if its bad other than if it looks obviously dirty/grimy or is visibly broken?

[MasterBlaster]

Originally Posted by tog244

there absolutely was something rattling around in my cat when i removed it, im not familiar with the insides of a cat but i assume it what 283sd called the matrix

(Pics borrowed from https://knowhow.napaonline.com/how-a...onverter-works)

Take a ceramic honeycomb with tiny holes running end to end.



Coat it with fancy and very expensive stuff (Platinum, Rhodium, Paladium).
Then wrap it in a protective blanket.



Insert it into a stainless steel sleeve of your favorite shape.



Protect it all in an outer shell with assorted flanges and O2 sensor holes.



And there you have a typical catalytic converter.




Physical damage, or running too hot can damage the insides, and cause the substrate (matrix, honeycomb, whatever) to come loose inside the shell, or actually melt.

It can also break apart into random-sized chunks. Sometimes a chunk can bounce around and turn sideways, blocking the exhaust flow.

[tog244]

very interesting, is there any way of saving it or is it just gone? If i had to guess itd just be a chunk of that honeycomb matrix thing- in which case can i remove that chuck hypothetically and solve my problem or is it not worth it?

[kampman]

Once the guts start coming apart it’s done for.

[tog244]

unfortunate, thanks tho

[Otto Mattik]

Originally Posted by MasterBlaster

(Pics borrowed from https://knowhow.napaonline.com/how-a...onverter-works)

Take a ceramic honeycomb with tiny holes running end to end......
And there you have a typical catalytic converter.

Master Blaster, runs Barter Town

[240Redblock]

$80 for new Cat, but must do a vacuum check to diagnose. I had this problem for quite a while, made sure to do full tune-up reset all timing etc. Finally pulled in-tank pump and found small pile of rust and dirt just below sock. Everything would run fine, but after long enough, the dirt would plug up the sock and it wouldn't get enough fuel through, used a magnet and replaced sock, been good for over a year now. Worth a check...