LUVTruck.com

I'm trying to get my LUV running as good as I can with stock equipment since I live in CA and have to keep all the emissions equipment. It's already passed twice but the last time around the guy told me it barely passed and said next time it might be a gross polluter. I really don't know much about this smog crap, my main car is a 67 el camino so I never had to smog it. All I really did to my 79 4x4 LUV since I got it was change the battery, dist. cap, wires, and plugs, rebuild the carb and replace all the vacuum lines.

Something that has always bugged me about my LUV is how loud it is. When I got it there was rust everywhere so I just figured it was exhaust leaks. I took it to a muffler shop and they only found one and after they patched it it was still pretty loud. From what I can tell most of the noise is coming from the catalytic converter and a little from the exhaust manifold. When catalytic converters get old or fail is that something that would happen? Or are those things always loud? I mean it makes more noise than the tailpipe. Is it just vibrating and needs a hanger to secure it to the frame?

I figured it probably should be replaced and then I saw they had all kinds of universal high flow catalytic converters on summitracing.com and was wondering if anyone here has used one of those and if it really helps it breathe a little better than the stock catalytic converter.

you might want to see if your donut needs replacing at the end of the manifold too. I've never had much luck with them lasting more than a week Mine blew out twice before I got a header. otherwise the best way for you to fix this would be to climb underneath with the engine running (preferably just after a cold start) and either feel around for what might be vibrating or feel for leaks too. Cats don't really "fail" the catalyst stuff either stops catalyzing, or it gets clogged and your engine won't run, or the stuff can crumble and rattle around a bit

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1980 LUV 4wd 1.8, 31's, 3" body lift, weber 32/36, header, fakemaster, project in progress
1989 Isuzu Pickup 4wd 2.6, 2.3 head, weber 38, header, flowmaster, 31's, DD/light wheeler
1989 Camry, the race car
1968 Ford Fairlane Fastback, next in line

It just sounds like a high frequency vibration/rattling so maybe there is some stuff that got knocked loose in there. A friend told me it could have be old and "hollowed out" and "you're hearing all the engine noise".

I do remember a few times when I first got the truck and I would start it it would idle super high (still does this half the time, the other half I need to keep the gas pedal floored while I start it). I haven't done this since but one time I started it it like that to warm it up in the morning and went inside to get my coffee or something and got distracted, when I came back out about 5 minutes later I noticed some smoke coming in the cab from the rusted out floor board and I peeked under the truck and the cat was glowing red hot.

I'm thinking of taking it to a different muffler shop to have it checked for leaks around the manifold and the cat, I got in there and couldn't feel anything obvious.

I was looking at the shop manual I just got and the catalytic converter does show a couple of flange mounts on the end that goes to the muffler.

I'm debating whether I should keep the stock manifold and cat. or get a header and a mangaflow universal cat.

I found a different cat. on summit that has an air tube coming out of it, maybe I can use that to feed the intake EGR using hydraulic line instead of that stupid steel pipe?

I've got an idea - post a video. rattles and vibration are difficult to describe via text, and beside that, you could be hearing a combination of issues. 'One thing leads to another', right?
A lot of the more experienced guys on here may have much better suggestions if given a little sound byte to go from - just a thought.

Regarding the high idle at start, mine did this too. It will die when you start it cold, but high-idle once it's hot. It ran fine on the freeway, idled like you said yours does, and sucked up a tank of gas waaay faster than it should. It turned out to be a big vacuum leak which wasn't really apparent until I busted out the carb cleaner and sprayed all the lines coming into the carb. I plugged the hole, and voila, no more high idle and shitty starting. Just the normal rattles and vibration

On that note, the stock LUV engine runs unreasonably, deceitfully well with a sizeable vacuum leak. Better than any engine I've ever been around. Can anyone else explain why? I couldn't believe it!

All that being said, a clogged cat can produce strange effects. The substrate inside of mine was crumbled to flakes and dust. Try rattling it around and seeing if you can hear debris shuffling around. If so, get rid of it. I don't know if you need anything fancy like a 'high flow cat', but I think you're sniffing around in the right direction. New ones on rockauto are something like 75 bucks.

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75 Mikado G180/4sp Desert Tortoise

I called Summit and the only one they could legally sell me was that damn Magnaflow high flow universal one that is about $190. I'll check RockAuto too. That one with the tube and one just like it without a tube are like $80 but I would need to get it shipped it to another state and have some kinda mail/package forwarding service ship it to me...

When I took the engine apart (it's being rebuilt) I noticed the donut seal on the exhaust manifold was broken into 3 pieces and it looks rusted on the outside really bad. I know part of the noise I was hearing was from that but the majority of it was the cat. and now that I see in the diagram that it was supposed to have it's own hangers maybe that is a part of it too.