80 Series catalytic converters need help (1 Viewer)

[BamaLC]

So second post regarding this issue - mechanic (if I want to call him that) says I need a new front cat to replace the aftermarket full line exhaust cat he installed in 2020 which is no longer under warranty. I never looked at the original before he replaced it. I bought an OEM one from Toyota but do I need 2? Did it originally come with two on the 1997 80 series? Looks like I have a front and a back that connect end to end. I got one in today but when I looked at it I could tell it would only replace one. If it takes 2, are they the same part number? Can I connect the one I have to the full line exhaust aftermarket second one. Plus I now have an exhaust leak coming into the cabin and I can’t tell where it’s from but assuming it’s at the engine somewhere. Frustrated and wish I could find a decent local mechanic.

 

[Godwin]

For a shop in Auburn I recommend Auburn Generator and Starter on North College at the RR track.

 

[jpoole]

97 came with 2 cats, in line with each other (vs. side by side on two pipes in parallel like the earlier 1fzfe). The front is integrated with the Y pipe and the second just has a flange on each end of the cat, stock. Post #15 here has some good pics:

Anyone using the magnaflow y-pipe and cats?

Anyone using the magnaflow y-pipe and cats? / Install Looking at replacing most of my exhaust (ypipe, 2nd cat, and muffler) and don't quite have the cash for OEM or EMS but also not sure I want to go down the bosal path either. Magnaflow makes at least the ypipe and 2nd cat. Is anyone...

forum.ih8mud.com

Here are a few cat part numbers that may be helpful though I'm not an expert and don't know if these are necessarily correct, have been superseded, etc. they are just quick grabs:

• 18450-66120
• 17401-66090

Some random cat/exhaust related part #s, same disclaimer as above:

• 90080-43036
• 90917-06076
• 90080-43033
• 90917-06065
• 90917-06043
• 90179-08059
• 17567-17010
• 90179-06007
• 90105-10388
• 94180-41000
• 17168-66020
• 17167-66040
• 90119-A0109

Additional related, aftermarket exhaust pieces and a cheap source for good o2s since that could be the issue also:

• magnaflow 23120
• Walker Sound FX 17853
• Amazon product ASIN B000C5WCRC
• Amazon product ASIN B000C5WCRW

In AL you could likely get by with one of the single cat setups from Magnaflow/similar which likely performs comparably to the oe 2 cat setup. Moving to a single horizontal cat could gain a bit of ground clearance and save some $$. I'd be wanting to know what you have now and why it's bad, ie. how that's been determined, etc. before I spent any money on it. My guess is you are no longer stock but who knows. A new mechanic may not be a bad idea as if it really is a bad cat you want to know why it went bad so quickly and address that as well or you want to fix what's actually broken vs. just buying new cats every few years. More info, pictures, etc. here and you can possibly figure out what's going on which could help you direct repairs even if the mech still does them.

The exhaust smell may be coming up through the shifter area seal as these do go bad over time. The steering shaft seal is another possible source.

• 33555-60071
• 45292-35050

 

[aclos3]

I recently had both of my (inline) cats stolen and I replaced the Y-pipe cat with the non-California Magnaflow unit. I then just had a shop connect the cutoff muffler pipe to the end of the magnaflow cat. The real pain was getting the Y-pipe off of the manifold. Bolts broke, so the manifolds had to be removed. Fortunately, everything was in good shape, so I did not have to replace the manifolds. I did use new gaskets and all new studs though. I still have both O2 sensors in their normal locations and I do not get any check engine lights.

 

[OffRoadScott]

With the newer LC with the cats inline of each other could you get away with one high flow cat? The O2 sensors are before and after the cats correct?

Unfortuantely I have a 94 and I have side by side cats and I myself cant think of a way to run a single high flow cat unless I delete the PAIR system and living in a State that requires emissions they might fail me for missing equipment.

 

[LandLocked93]

I wish I knew how to get another of the 2-to-1 cat in my 93. If it didn't come from the factory this way (yes I'm aware 'they did not', I don't know either way) it sure was made to fit there.

What I don't get is why the factory shield that can be seen from the side fits this single cat. It is not an inch too short or too long. It's is an exact match. And there is not room for 2 cats to have ever been in place there and still fit between the rails and body AND fit behind the shield.
Just strange...a true unicorn (unicat?)

 

[Pascoscout]

I replaced the two inline cats on my 1997 with a single and have not gotten any codes. There is a bit more "fuel" smell out the tail pipe but that's it. I can't tell you if they are the same part number, but you only need one if you're in a state that doesn't do emissions inspections. If you want to keep it factory then yes, it originally came with two.

For your exhaust leak it's probably coming from one of the joints in the system. If the installer used non-OEM gaskets they don't tend to hold up. I used a good name aftermarket brand when I first did my exhaust and they lasted maybe 3 months. Went to the OEM gaskets (which honestly were only a few dollars more) and they've been fine for a couple years now. The aftermarket ones looked like they had burned up when I pulled them out.

 

[subzali]

Just because it’s no longer under warranty doesn’t mean it needs replaced. If you’re passing emissions leave it alone until you’re not.

 

[BamaLC]

What if I cut the cats out altogether, leave the front 02 sensor, and then they make a rear 02 sensor that will read clean as I understand it. Mechanic says can’t recode a 97 to cut off any check engine lights so need whatever this is he’s talking about to basically trick it into thinking it has one, so front reads dirty and the rear just reads clean air somehow. Wish I knew more to tell you but sounds like it’s a way to mount the rear sensor to where it maybe is on the outside somehow. Honestly I have no idea. One thing is for sure, the cat has to go cause it’s stopped up and limiting performance it seems like. So it’s either do another aftermarket like Magnaflow, pay Toyota $1600 for front and $500 for rear OEM, or cut them off. Muffler and tailpipe are all brand new Borla just FYI. Also for exhaust leak, he ripped off the heat shields and I’m betting there’s a hole or something at the cat and it’s causing exhaust to come inside. Also seems worse when heat or air is on.

 

[Godwin]

If you're going to replace parts go with the Magnaflow pipes with cat plus the second cat. These parts will bolt up to your new Borla exhaust and that should fix the leaks and keep the exhaust intact. Don't forget to use new gaskets and nuts and bolts.

Is the mechanic advising that you rework the exhaust to trick the computer in some way to avoid reworking the exhaust properly? If so I'd find a new mechanic.

 

[BamaLC]

With the newer LC with the cats inline of each other could you get away with one high flow cat? The O2 sensors are before and after the cats correct?

Unfortuantely I have a 94 and I have side by side cats and I myself cant think of a way to run a single high flow cat unless I delete the PAIR system and living in a State that requires emissions they might fail me for missing equipment.

Godwin - I have the lower end OEM that I paid $530 for at dealership in Auburn. Do I need to go with the magnaflow 23120 for top end? I think gaskets may be linked up above?

 

[Godwin]

The Magnaflow 23120 would substitute for 17410 in this parts diagram.

 

[Bambusiero]

What if I cut the cats out altogether, leave the front 02 sensor, and then they make a rear 02 sensor that will read clean as I understand it...

The ECM will bust you for that...The ECM (Engine Control Module) works like this:
- it bangs back and forth between 1) too lean, where the upstream O2 sensor reads about 0.0V, and 2) too rich, where the upstream O2 sensor reads about 0.7V - the waveform looks like a square-wave.
- The cat is supposed to (very temporarily) store a bit of the excess O2, then a bit of the excess fuel, which then reacts with the opposite condition coming along soon. So...the cat is supposed to sort of "low pass filter" the exhaust gas stream, outputting a gas stream with an average - nearly balanced fuel/air mix. - The waveform looks like a slow triangle wave, or at least a ramped trapezoidal squar-ish wave.
The downstream O2 sensor should read about 0.4V (balanced) at least sometimes. With no cat there, or - effectively no cat, because it has become old / coated with ash residue, then it is essentially a tube and not a cat anymore.
- Then the ECM will throw an OBD2 code saying "catalytic converter efficiency low" (if the downstrean signal also looks like a square-wave).
- You can actually see the waveforms of both upstream and downstream converters and see this stuff going on, and conclusively diagnose these things.
- With an inexpensive plug-in bluetooth OBD2 reader and the "TorqueLite" Android App. I use an iPhone, which, unfortunately has no OBD2 reader App available - I keep a somewhat obsolete Android phone around just for this necessary(once-in-a-while) tool.

Of course - if you have electronics skills, you could build a little "downstream O2 sensor" simulator - if your are really that motivated NOT to simply have it all work the way it's supposed to...I guess.

 

[Bambusiero]

With the newer LC with the cats inline of each other could you get away with one high flow cat? The O2 sensors are before and after the cats correct?

Unfortuantely I have a 94 and I have side by side cats and I myself cant think of a way to run a single high flow cat unless I delete the PAIR system...

Yes, it seems that quite a few have gone from 2-inline to only one, and they report no resulting OBD2 problems.
But - it's different than your side-by-side, because the exhaust gas streams of cylinder 1,2,3, and 4,5,6 are mixed (averaged) prior to being evaluated for the closed loop ECM fuel control. Your 94 ECM is expecting to see, and react to, three separate O2 sensor signals (I think so?).