There was a n exhaust leak cause the header pipe was malformed,,so I got a clamp from napa that locked onto both sides & forced them to seal..so after that Ive been having loads of problems including bad MPG for the last year & finally it started dying & I could figure out why,,then I remembered the same problem happening w my 89 740 ..The Cat was clgged w carbon, I took the o2 sensor out & wallaaa it started right up!!
Has anyone tried to flush the carbon out??Im thinking to use hotwater??to back flush it??I saw 1 advertised on ebay but dont want to waste it if I could flush it!!

Too much Oh Two at the sensor, makes LH-Jet pump more fuel, A dense charcoal briquet in the making inside your cat.

So, new cat time. If too long in the cat, the carbon material gets very hard inside the ceramic matrix. So Solvent exists to dissolve it and the damage to the ceramic matrix is irreparable.

You are in NJ-state?

Effective May 2016, cars 1995 and older are no longer subject to emissions inspection. Safety inspection may note a strait pipe with o2 bung hole. I'm not sure if NJ safety inspection inspects for emission controls.

The inside the air filter box preheat flap valve works ok, or is not stuck, or if stuck, removed as a cold air intake?

https://en.wikipedia.org/wiki/Vehicle_inspection_in_the_United_States
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Beh.

it's not carbon blocking the convertor, the convertor itself is melted and blocking flow.

Cat is only a bout 2 years old>? Shouldnt melt that faST?/

should it melt-no.

can it melt that fast-yes. running too lean overheats the cat. vac leak, bad amm, low fuel pressure, etc. all of which should pop a check engine light. also, cheap parts. an oe volvo cat is always the better choice. true of any car. the 98 up volvos have to have the oe cat because the non oe ones do not do the job and the p0420 code persists.

Dear porkface,

Hope you're well and stay so! If the clogged catalytic convertor were heated strongly - say, to 1,000°F - and oxygen were blown into the opening, wouldn't the carbon "burn-off'? If so, could this be a way to de-carbonize a plugged unit?

Stay well!

Yours faithfully,

Spook

carbon is not the problem, the catalyst has melted. never seen a carbon clogged cat, just melted.

Doesn’t the cat have a warranty?
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Will I buy another Volvo??? We'll see....

iT DOES FROM fcp but THEY DONT STOCK IT ANYMORE!!!

MY CRUMMY LENOVO LAPTOP IS HARD TO TYPE ON WITH

iT DOES FROM fcp but THEY DONT STOCK IT ANYMORE!!!

Im going to try & reverse blow it out w my shop vac...