sbwest

So I was getting error codes for bad '02 sensor readings until today while driving on the freeway my car suddenly lost acceleration and started to bog down. I'm barely able to accelerate at all now with the same codes being present(p0156, p0430).

I took it to a shop and the mechanic said I have almost a completely clogged catalytic converter on my exhaust manifold... The one that is dead in the middle of it.
He informed me that since my car was originally sold in Cali, it is a California complaint car and requires California compliant catalytic converters which are built differently.
I recently swapped the exhaust manifold to an OEM equivalent about a year ago and it turns out it is 49 state legal and not California compliant which is why it apparently clogged according to him.


Other than another entire replacement exhaust manifold, is there a MacGyvered way too reduce the back pressure on the exhaust manifold's Cat so I can regain a little bit more normal acceleration? Drill a hole in the manifold before the blockage? Drive with lacquer thinner?

Doesn't need to be a permanent solution but I'm intending to sell my GS as I'm tired of working on it and it needs to be drivable for me to be content with selling it as a mechanics special lol
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​​​​​​ For reference it's a 2003 black sport design(yes saddle). 213K on the body and about 70k on the engine.
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firelizard

iTrader: (1)

Magnaflow sells CARB legal replacement cats.

Drive with lacquer thinner? Come on man.

Ps: it's clogged because it's not CARB legal? Maybe consider getting a different mechanic, that is the most bizarre explanation. It's not like 49-state cats are allergic to air in California.

sbwest

Last muffler shop I asked to swap the cat on the exhaust manifold told me they were unable due to the location. I'll ask around for more opinions.
The lacquer idea is something I saw a few mechanics used to do, essentially a cheap fuel additive that breaks down deposits in your system. Supposedly it isn't harmful in smaller amounts.
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I thought it was odd but it was his only idea since the engine is newer, there are no other codes, and the carb is less than a year/20k mile old. He came to the idea since there's the variable of a Cali vs 49 state part and the vehicle is from Cali but I'm using a 49 state-legal since I'm out of state.

DundukovEM

If you have or can find somebody with basic welding skills, DIY in 5 easy steps:
- remove the exhaust manifold,
- cut off the sections with angle grinder of both cat converters,
- throw out all guts from there (chisel / hammer / crowbar works good),
- weld the original sections back on it
- install on the car

Works like a charm!
I have seen many times how this is done on many cars in another side of the world car market.

TrueGS300

If you just need it to be driveable to and aren't worried about passing smog, there are $75 IS300 headers available on ebay. I installed a set once that fit fine and it will probably be your cheapest solution to the current issue.

sbwest

I'll be trying this next.
I read online that The manifold is interchangeable but the y pipe is different...
Will I need the IS-300 y-pipe as well or Will the manifold be a direct fit?

TrueGS300

Just the headers. They are the same for both cars. If you do an intermediate pipe, order the GS specific one because that's whats different. They are cheap so expect to do a little caressing to make it happen. For me, I had to shave down the motor mount bracket so they were't wedged up against it and not letting the manifold gasket seal properly on the under side. Others have reported not having to do this. But basically, they bolt up. Should be good for what you're trying to do.

TrueGS300

Oh I forgot to mention, if you want to keep the codes from coming back, you will need to order two o2 extenders off ebay as well. These need to be installed for the two downstream o2 sensors to keep them pulled back out of the exhaust so they don't sense that there are no cats these. Not the two upper ones. They need to stay in the exhaust like normal for the car to run right. Only the downstream will throw cat codes if the extenders aren't installed.