amvmr

Can someone watch this video and please guess/tell me what is making the loud knocking noise. 2000 Honda Civic GX. Thanks

The video is of a cold start and at the end some water can be seen dripping from the exhaust pipe flange.


Car has been running but under-powered for a few months until finally something gave out and now starts, idles, then stalls, not enough power to driver the car anymore. Feels like the engine is getting enough fuel to rough idle but not enough to run.

ezone

Sounds like a garbage can full of rocks!
Is that coming from the engine, or from the exhaust?
Did the engine get run very low of oil?


Get under car (cold, not hot) and use your hands to bang hard on the exhaust. Does it rattle like it's full of rocks? Cat may have come apart.
Has the engine been misfiring? That can ruin the cat.


Water coming out of the exhaust is normal and expected.

amvmr

Coming from Exhaust. No engine oil looks fine. Never overheated so I think eng is fine.

Part II
1. Since I bought it the exhaust has been and is now making a sputtering or puffing gas release sound so I took the following video. I suppose this is bad...
Also now while idling I can cover the exhaust pipe outlet with my hand and completely block all exhaust trying to escape.



2. I am very confused on this car 2000 Honda Civic GX CNG (Natural Gas, California) does it have one or two catalytic converters? The first unit is directly attached to the exhaust manifold visible when you open the hood. The second tube shaped unit in the middle of the car (seen in both videos) half way between the engine and the muffler? I was looking for a replacement for the 2nd tub shaped unit on ebay but most of them looked hollow making me think that mine cannot be clogged at this point.

Thanks

ezone

According to a dealer parts catalog, the car has TWO cats. First one is contained within the big round part of the exhaust manifold at the engine, the other is the fat tube under the car, seen in your video.

The cats are not supposed to be hollow.



That is definitely a catalytic converter in your video, and the exhaust is definitely clogged. When you tried to rev up the engine I can see the spring loaded joint (between first pipe and cat) open up to let excess pressure out. You can watch that cat move back!



SO how much rattling happens when you bang on the exhaust with your fist?


At least one of your catalytic converters has probably broken apart, and its guts are now in chunks bouncing inside the pipes and clogging up the flow. If I had to guess, probably the front converter came apart and its pieces are clogging the second cat.


SO you have huge cat problems. If you are in California, you are probably going to have to have both of them intact and working in order to pass emissions.

Now...what caused the cat to fail in such a catastrophic manner? Poor running, severe misfire, excess or raw unburned fuel are some of the usual causes of cat failure.
(it really sounds like the engine has a dead miss when you are revving it up, and I bet it was running like poop right before it broke the cat apart)

So...before you just go get the cats fixed, you need to fix the root cause, the poor running problem that ruined the cat.

I would unbolt the spring loaded joint between the front pipe and second cat just so the engine can run, so I could figure out how well or bad it runs (it will be loud) and diagnose or fix it.
You will probably find a pile of cat substrate stuck in the front of that second cat when you look into that pipe. It needs cleaned out, but that second cat may have been ruined as well.