blitzur

So, I think I did a really dumb thing, and was looking for "something" to justify my madness! Or laughter and humiliation, whatever is justified for this project...

Before
My 2002 LS1 Trans AM has 140k miles, and was running just fine. No check engine lights or anything. It was entirely original and completely stock.

Story
Browsing the classifieds, I found a near new set of original OEM catalytic converters and Y-Pipe from a 10k mile 2000 Trans AM. They looked brand new, so I didn't question the mileage....

Based on the price of the 10k set, and the recycle value of my old set, I originally thought it wasn't going to cost that much to "upgrade" to the low mileage cats. Why I was doing this - I DON'T KNOW YET!?!

So I decided to have my 140k Cats and Y-Pipe swapped for the 10k ones. The guy I had do it even called me mid-stream during the work, and asked, umm, so the pieces I am putting on are exactly the same as the ones I removed. I said yup, and he continued on...

After
Every bolt on the cats broke, but I was told none of the manifold bolts broke... So, this supposedly good news.

Gaskets were reused. One was in bad shape, so high temp silicon was used. You can smell it... Stinks!

So at first, it drove the same. Then after 3 miles, I noticed the RPM's going real low and the car almost stalling when coming to a stop (has auto trans).

After 8 miles, the "Service Engine Soon" light comes on....

Exhaust still stinks..

So, next steps?

1) I need to get the code(s) and see what is failing.

2) Based on that - possible bad O2 or bad CAT - what should I do next? Go back to original CATs, or?

3) Why the heck did I do this in the first place - this is the part that is KILLING me?!?!! Arrgh!!

SSCamaro99_3

iTrader: (1)

Last I recall 98-99 are the same, 2000 is different, and 01-02 are comapatible. So you probably have some mismatched crap going on.

blitzur

I did some checking, and from what I can tell, only the manifolds were different. CATS are the same..

An update though - I grabbed the codes. Getting a P0174 and P0300 now, and the car is running like crap.

P0174 - Bank 2 running lean.
P0300 - Random misfire.

From what I can find, possibly have 3 issues? Anyone have experience with these?

Possibilities:

1) O2 sensor front and back plugged in backwards
2) Exhaust leak
3) Bad O2 sensor? - Leaning towards this one!?

Thanks for any advice!

Bramlok

iTrader: (7)

If you weren't having problems I would have just left everything alone.

It's possible if the silicone was not sensor safe, that could be messing with the O2 sensors. Even if it's high temp stuff I don't see how it could survive for long with the high temps of manifolds and cats.

Options are put your old stuff back on with NEW gaskets and possibly new O2 sensors.

If you want to upgrade to headers and high flow cats, this would also be a good time to do that.

blitzur

I certainly wish I had left it alone! Unfortunately too late for that now, so must forge ahead.

Very good point on the sealant being sensor safe. I will have to ask the guy who did the work about that one.

I also wondered about it lasting with the heat of the cats. What a mess...

But moving ahead, the way I understand it is there are two O2's per side. One above each cat, and one below. The bottom ones don't affect the way the car runs, but can trigger the SES light to let you know a cat is malfunctioning.

Being that my car is running like crap, I'd say a top O2 sensor is bad. Code says bank 2, so passenger side, right?

I am thinking after 10 years or not being disturbed, then removed and reinstalled, the O2 sensor probably went south.

Or the sealant got to it...?

I guess I am looking at the most affordable way out of this mess and to get the car driveable again.... Help!

Should I try an O2 sensor? Any brand recommendations? And is that an upstream or downstream one?

Exeodus

iTrader: (1)

Wouldn't the sealant be aft of the front O2? And if it is, it wouldn't matter if it was sensor safe or not. If it did damage the rear O2, it wouldn't cause any drivability problems, just an SES light. Keep in mind if the newer cats had 10K miles on them, they could still have been clogged up if the engine they came from was running rich.

blitzur

What are the symptoms of a clogged up cat? Would it cause the car to almost die when coming to a stop? And make the car run horrible, and throw misfire, lean codes?

The next mechanic I have in mind for the repair also thinks the "new" 10k cats are the problem - but for some reason I still have some faith in them.

I guess I was thinking to start with the top O2 sensors, and then if still an issue remains, then the cats are bad - and I will revert to my old ones. But again, thinking is what got me here in the 1st place!

I already ordered the O2 sensor, it is sitting on my doorstep waiting for me. Since I have that, I will put that in next and see what happens. I don't think it can get much worse!

SunsetOrangeZ

iTrader: (10)

A clogged cat will be very hot. At one point it will start glowing orange. So get the car good and hot at night and take a look.

Most likely sounds like a bad o2. And also if the cats were bad, you'd be getting codes from the rear o2's.

blitzur

Ah, thanks!! Based on this advice, I went ahead and swapped the upper O2 sensor on the passenger side.

That fixed it! Runs like a champ again. No more misfiring, running rough , or SES light!

This would have taken 10 minutes - BUT of course while under the car I noticed the radiator drain plug... which started a chain of events. So, I ended up cleaning the under carriage, applied rubberized coating underneath, cleaned/degreased the engine bay, flushed and changed the coolant, replaced AC belt, etc...

But now it has gotten me thinking, should I also replace the old original O2 sensor on the driver side?

Can they be degraded and hamper performance before a SES light would be triggered? I am thinking the car is running a little bit better now - before it had these recent troubles. Since the O2 I removed from the passenger side was black as coal and tired/beat looking. I guess it couldn't hurt to also swap the driver side, but is it a waste of money?

What is the interval for O2 replacement? Or is it a simple good or bad scenario?

TImmy_Jones

iTrader: (4)

They either work or they don't....I wouldn't replace one if it works fine. Change your spark plugs and wires with that money, better maintenance there.