Cat or muffler blockage

[bytes311]

Hey Guys,

Today I started up my car and found that the exhaust is plugged somewhere. I attached a photo circling the area of where it got hot (it actually glowed bright red). Any idea if that type of blockage is related to the cat, or the muffler?

Thanks.

-Daniel

32771

[hmcelraft]

I've seen them glow when the engine is running too rich with fuel. The cold start valve is sticking open, leaking injector(s), control pressure gone bad, etc. That will eventually ruin the Cat and probably clog it. A restriction usually just causes poor off idle performance - unless completely clog - then it would not run.

[DavidProehl]

I've seen them glow when the engine is running too rich with fuel. The cold start valve is sticking open, leaking injector(s), control pressure gone bad, etc. That will eventually ruin the Cat and probably clog it. A restriction usually just causes poor off idle performance - unless completely clog - then it would not run.

Agreed, a glowing cat means it is running rich. Another possible (though unlikely) cause: a misrouted wires from the distributor to spark plugs. After doing a VOD job on my car I had two wires swapped. This meant fuel wasn't igniting at the proper time and instead going to my cat. If you have recently done your wires, double check them. Funny thing was, I didn't notice much loss of power when driving like this, though I never drive the car hard.

[David T]

Agreed, a glowing cat means it is running rich. Another possible (though unlikely) cause: a misrouted wires from the distributor to spark plugs. After doing a VOD job on my car I had two wires swapped. This meant fuel wasn't igniting at the proper time and instead going to my cat. If you have recently done your wires, double check them. Funny thing was, I didn't notice much loss of power when driving like this, though I never drive the car hard.

If the car was running OK and now it's running rich my first thought would be a sticking plunger in the mixture unit. Was any service work done recently? Did anyone mess with the mixture adjustment?

[bytes311]

Thanks for your comments!

It must have clogged due to the rich fuel mixture dumping fuel in, and years of sitting. Before I cleaned the air idle solenoid, the Cat didn't glow, but when the engine started working fine, it glowed. This happened immediately after I fixed all the vacuum leaks and the engine started performing great. The engine used to idle hunt and sputter.


If the car was running OK and now it's running rich my first thought would be a sticking plunger in the mixture unit. Was any service work done recently? Did anyone mess with the mixture adjustment?

Yeah, see I don't know what was done to it in the past. I purchased the car back in September, and it always seemed to idle jump until I fixed that by eliminating the vacuum leaks. The engine ran great for a while (2-3 minutes), but then it started getting hot.

[bytes311]

Welp, now it wont start at all. It cranks fine, and it doesn't sound like it's starving for fuel. The exhaust is gray/black. Guess I'll be removing the Cat tonight.

[dn010]

When my cat went bad, all the crap from it lodged and blocked up my muffler, when I had the original system...

Also, have you tested your injectors using the clear jar/bottle method? That may give you some indications of what might be wrong if this is all related to your fuel distributor or injectors...


Welp, now it wont start at all. It cranks fine, and it doesn't sound like it's starving for fuel. The exhaust is gray/black. Guess I'll be removing the Cat tonight.

[DavidProehl]

Also, have you tested your injectors using the clear jar/bottle method? That may give you some indications of what might be wrong if this is all related to your fuel distributor or injectors...

Along these same lines, did this car sit for a while before you bought it? If so, your fuel system may be gummed up. It could run for a while until debris works its way into the distributor and injectors.

[Jonathan]

It looks like you already have it figured out that your cat is plugged, but another way to determine where the restriction is would be to see where the red hot pipe ends.

Meaning, if it were a pipe carrying water or some other liquid or gas and there was a restriction, like a valve not open all the way, you would see a higher pressure on the upstream side of the problem, and then beyond (downstream) of the problem, it would be back to normal, or perhaps even lower than normal in the case of fluid pressure.

It wouldn't be all that likely to see a restriction in only one of the headers or one of the cylinders, but wherever you can see that the hot and red looking pipe stops and has its normal colour or appearance, that's where you go looking for the problem.

[bytes311]

Also, have you tested your injectors using the clear jar/bottle method? That may give you some indications of what might be wrong if this is all related to your fuel distributor or injectors...

I will try this method tonight. Last night I pulled the spark plugs, which were indeed wet. I cleaned them up and the engine started up, but would die immediately when idle. The Cat AND the center of the muffler got hot this time. However, the exhaust coming out the pipe felt strong.