O/T Cat Convertor

IndianaRed · Jun 25, 2009

I know modern engines are engineered to need the resistance from the convertor, but what would the affect be on my '06 4.8 Chevy if I were to cut them out? Maybe just temporarily.

Kruse · Jun 25, 2009

On cars that have an OBDII system, you have an oxygen sensor before your catalytic converter and you have one after. The rear O2 sensor measures how much of an emission difference is between the front and the rear. If you take the guts out of your catalytic converter, there will be no difference between sensors and your trucks computer will throw a CEL (check engine light) and run worse than if you had a working converter.

IndianaRed · Jun 25, 2009

I figured it would cause a check engine light, but I thought maybe it would just go to default code. I think my cats are either plugging or deteriortating as I'm getting intermittant check lights now. Only thing I don't like about this truck is that it has two cats instead of one.

RobMD · Jun 25, 2009

A new Honda accord has three cats. Isn't that crazy?

IH2444 · Jun 25, 2009

Screen type of converter or monolithic block type?
The screen type are very hard to plug.

IndianaRed · Jun 25, 2009

Don't know the difference. Looks like most others I've seen from the outside.

Sean Feeney · Jun 25, 2009

What codes are you getting?

Sean Feeney · Jun 25, 2009

What codes are you getting? you will get a check light for a loose gas cap

IndianaRed · Jun 25, 2009

Well, for the last 6 months I've been getting mass air flow, and it said possible cause could be cat convrtr., misfire, etc. I've check MAF and it's clear and wires look ok. But this last time it just said cat convtr, bank something. Makes sense to me. I pulled a heavy load a lot in 3rd and 2nd gear all day for many days over the 1st year after buying new. I'm up to 315,000 miles, so they're probably due. Just when I'm short in $$ of course.

Wish it was a loose cap, but it's not.

Brian Jasper co. Ia · Jun 25, 2009

It will not run worse if you removed the converters, but you will get a check engine light with codes for low catalyst efficiency, 1 for each bank. If you think you have a restricted cat, get a back pressure gauge that screws into the pre converter sensor hole. GM's spec for back pressure is a max of 1.5 psi @ 2000 rpm no load.
Summit Racing Equipment used to sell a device that mimicked a good after cat signal for "off road use only". Last I knew, they didn't sell them anymore.

504-2 · Jun 25, 2009

Ford used 5 for years,2 pre cats on each bank and the main after. An after market cat is about 35.00,you just have to look around for them.

IndianaRed · Jun 25, 2009

I've been looking and haven't seen anything nearly that cheap. Guess I'll keep hunting.

IndianaRed · Jun 25, 2009

Thanks Brian, I think I can live with the engine light on for a while. At least until they give me my bailout funds.

buickanddeere · Jun 25, 2009

The engines were NOT engineered to require back pressure.
These people who think an engine requires back pressure or intake restriction have odd ideas indeed.
For one thing the OBDII system knows about people like you. When the rear O2 sensor output begins to oscillate. The computer is going to throw a failed converter code.
Just how many HP are you expecting to gain? The monolithic converters of the past 25 years bare no resemblance to the awful pellet converters of the 1970's.

buickanddeere · Jun 25, 2009

It needs three cats to meet cold start emissions laws.You can thank the well intentioned the clueless tree huggers who wan to ban technology.

Anonymous-0 · Jun 25, 2009

I hope I am wrong and maby I am the only one thinking this was but at 315,000 plus miles could the engine be nearly done ?

IndianaRed · Jun 26, 2009

No reason to think so. Starts/runs like new, same fuel mileage and maybe a little better, idles smoothly, same oil pressure, no trouble codes for motor. One of the other guys is up to 550k on his, same make/model.

IndianaRed · Jun 26, 2009

Not trying to gain any horsepower. Just a little low on funds currently and wanted to throw some pipe in for a while until I can better afford cats.

supergrumpy · Jun 26, 2009

MAF sensor sometimes get buildup on them, good cleaning with carb cleaner sometimes fixes them, not that expensive to replace

dirty MAF on my son's Taurus gave O2 sensor codes

Brian Jasper co. Ia · Jun 26, 2009

Having worked at Ford dealers, I can say they never had 5 catalytic converters. Also, NOBODY sells catalytic converters for $35. Scrap yards typically give $75 for junk converters.
Replacement converters typically cost $500 to $800.
Like I said before, test the back pressure before putting on replacements.

IndianaRed · Jun 26, 2009

I've been seeing cheap ones online for around $185, but have to wonder about the quality. Is that tester something I could borrow from the parts store?

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