Intel's Ronler Acres Plant

Silicon Forest

Thursday, August 8, 2013

Catalytic Converter

A very pretty 318 engine installation, to compensate for the rest of this story.

Younger son calls me on his way home from work yesterday. The truck is acting up, it's hissing and it won't go over 45 MPH. We talk a bit and rule out the basics like overheating, running out of fuel or catching fire. He drives it home and we take a look. Nothing obvious, so I start it up. It hesitates bit on starting, which is not normal, but then it idles okay. But it doesn't sound quite right. And there is that big hissing sound. I rev it up a bit, and it does speed up, but reluctantly. Hmmm. Shut it off and then I realize the one big clue is what was missing: the throaty roar of a V-8 engine. A quick search on Google clues me in. Now I put two and two (or clue and clue) together. What was the first clue? The catalytic converter has been rattling to beat the band for several months now. It only does it at idle, once you get going it stops, so "Converter Plugged" could very well be the problem, i.e. something in the converter has broken off and is plugging the exhaust pipe.
    This sounds like a job for a muffler shop, so this morning I try and call Ed's Mufflers. They did a brake job for me 20 odd years ago. That's funny, I find all kinds of listing's for the place, but no phone number. I finally locate one, but when I call the number has been disconnected. I could have sworn I just drove by there the other day. Oh well, we'll call Hortnagl. He's farther away, but he was highly recommended, although that recommendation was 20-odd year ago. He confirms my diagnosis and then starts inquiring about the vehicle. I tell him it's a 318, and he says there is no such engine in that truck. He gives me a choice of a six or an eight with some metric displacement. Okay, fine, it's the eight. He should be able to fix it today so I drive on over. "Drive" is optimistic, coax is more like it. It won't go 35 until I let off the gas which allows it shift into drive. It's happy as long as it is not turning much above an idle. 2500 RPM is only a dream of past glory.
    Mr. Hortnagl runs a little one man shop. He's been there for 33 years. This is the first time I have ever used him. After talking to him on the phone (he has a bit of an accent) I assumed his preference for metric displacement was because he was from Europe where everything is done in metric all the time (except for England, where everything is done in bonnets. Or spanners.), but no, that is not the case. Along about 1996, American car manufacturers dropped the cubic inches and started using the metric system to define engine displacement, and being immersed in the automotive trade he went along with the new convention.
    Well, that's all well and fine, but calling 318 a 5.2 liter doesn't make it a new engine, it's still a cast iron 318 cubic inch V-8 from 1957. Or 1967, if you want to be picky. So Mr. Hortnagl has adapted to the changing automotive world while I am the old fogey stuck reliving past glories.
    Earlier I was thinking that the design of this converter was poor in that it would fail in this manner. Then I realized it might have been done deliberately. If the converter is so old that it is falling apart, then it probably needs to be replaced, but no one will bother replacing if it isn't causing any problems, so voila! Let's have it make a problem. No testing, no bureaucracy, and it doesn't kill the car completely, it just makes it really annoying to drive. Genius.

Here is a view in one end of the converter. You can see a grapefruit sized chunk of the catalyst honeycomb inside. It's totally loose and free to roll around in there.

    Only problem with this is that emission testing here doesn't really test the emissions any more. They used to have probes they would stick in the tailpipe and actually sample the actually exhaust gases (actually!), but now they just plug in their computer to the vehicle's computer, and two computers hash it out and decide whether you are worthy or a sinner.

Here is a smaller chunk of the catalyst honeycomb that fell out on the floor. If you hold it up to the light and hold it at just the right angle, you can see light through the holes. I tried to take a picture that would show this but I couldn't get an image on the camera's low resolution screen that showed light through the holes.

    So if the catalytic converter has worn out, then it wouldn't be doing it's job anymore, so how come it passed emissions testing last month? Maybe there aren't any sensors downstream from the converter, but that seems contrary to the draconian emission policy we have saddled ourselves with. In any case, I didn't see any sensor when I was looking at it last night, but Mr. Hortnagl says there is an O2 sensor down there. Somewhere. I'll take his word for it.


CGHill said...

There's always a downstream sensor. Its job is to report what's coming out of the cat, thereby completing the feedback loop. (Which doesn't mean that someone hadn't pulled it years ago; but it's supposed to be there.)

Charles Pergiel said...

That makes sense. I am pretty sure the computer would complain if it was disconnected. I still wonder how I managed to pass emissions testing last month.