Plugged cats?

[SVTContique]

So I've got an aftermarket H pipe that i catted with magnaflow high flow cats a couple years ago. Anyways, the car seems to "die out" under load. At first i thought it was a fuel issue but my wideband is showing normal AFR. No bucking so it's not a spark issue. I figured plugged exhaust was the next alternative.

It's there a way to check for plugged cats? Even if i pull the pipe off I'll only see the front screen of the cat anyways correct?

 

[Wynn]

Does it do it at any specific Rpm?

 

[Wynn]

It almost sounds like a weak fuel pump to me

 

[PSUCOBRA96]

you can pull the h or x pipe off, shake it around and hear if the pieces have started to deteriorate and coma apart, it will rattle when it should be solid and make no noises.

You could also plug one end up and use compressed air from the plugged side and see if you can get air past the cats fairly easily, I would suspect it would flow fairly easy on high flow cats but I could be way wrong on that aspect.

 

[1989Gt.]

My car would surge when my cats got clogged. So your issue sounds different then mine.

 

[CzchMex]

If you hit your cats when they are cold you will hear stuff loose inside if they have gone bad. Also if they are clogged and you run your car hard. You can sometimes see a faint glow on the cat itself bc they have so much restriction. Works best if you don't have heat shields and it is at night.

 

[SVTContique]

Does it do it at any specific Rpm?

Not really, more or less when i put more load onto the car, like once it gets out of open loop.

It almost sounds like a weak fuel pump to me

Wouldnt my AFR be all wack then? Like shouldnt i be running lean if the pump is toast?

 

[DVJ38]

Why not just take the midpipe off and stand on it. See if it revs up normal or if the problem is still there.

 

[nckissfan]

I was told if you run the car awhile, then look underneath at the cats and they are glowing, they are clogged

 

[phinhead34]

My cats got clogged on a vette I had and the car had no power under load. Removed cats and problem solved.

 

[Expurple]

From what I have read in the forums it seems to be the symptoms of a stuck/malfunctioning IMRC system.


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[Mustang Matt]

My cats made terrible rattling sounds once they were dead. I thought it was the transmission. Put it on the dyno and they exploded out the tailpipes.

Recently I've become aware that there's a chance for pistons to swell under this condition (too much backpressure). I'm still reading up to see if this is a real thing or not.

 

[SVTContique]

So it got warm finally today, pulled the exhaust system basically apart. The cats seem fine, started the car up and the air was blowing out of both pipes totally fine with no real restrictions.

Car is still acting up however and im sort of losing patience, There is NO CEL, no changes in AFR, no drops in oil pressure or anything...

If it were a spark issue it would be backfiring and jumping under load, this just sounds different, when i get under load the whole car sounds different, like something is wrong and the exhaust changes note completely.

Any other ideas?

 

[Helomech74]

Do you still have IMRC's or are they deleted?

 

[SVTContique]

Still has them, but its not even acting weird at the point where they should be opening, its all throughout the power band.

 

[STAMPEDE3]

Plugged cats and broken cats are 2 different things.

Broken, they will rattle if you hit them. They normally don't affect much unless the front of it breaks into pieces and clogs the rest or restricts flow or depending on your muffler design they can come apart enough to get caught and clog there.

Plugged, they will not rattle but as said, the car is normally down on power and they will glow after running a while.

 

[SVTContique]

^^^ yea mine doesnt do either of those things, im thinking its something else now.

Fuel pump, injectors, MAF, plugs, wires... ugggh.

 

[Cobra52898]

Dirty/plugged up air cleaner?

 

[SVTContique]

Like air filter? It shouldnt be, i cleaned it in the fall, i suppose i could try cleaning it again.