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Discussion Starter #1
My wife and I had to run a couple of items out to the summer camp where our daughter is working. Along the way, there was a one mile long uphill grade that peaks at about 7%. I crested the hill flat out at 50 MPH and was losing steam. About half way up the hill I killed the A/C (although full throttle will do that for you) without any change. This isn't normal. I went up the same hill less than a week ago with a fully loaded car with 3 people in it, and didn't have this problem, although the car did seem to struggle with hills more than I would have expected.

Since then I've installed a new TPS, replaced the fuel filter, and installed new rear brakes. The TPS reads 95% with my right foot on the floor and 18% at idle. That looks okay. The rear brakes aren't dragging.

As I got towards the top of the hill, the engine was starting to surge a little bit. But, not other indications of distress. No misfiring, no pinging, no black smoke. But, there was a slight exhaust smell in the car.

Usually, a systematic power loss is lack of fuel, breathing issues (can't get air in or exhaust out), or ignition/valve timing issues. On the way home, the OBDII readings looked normal.

My first thought is plugged cats. But, that's a secondary issue since the engine has to be running too rich or misfiring to get there. I've been chasing an intermittent cold start misfire issue for some time. Maybe that has finally taken it's toll.
 

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Discussion Starter #2
Here's some data from the ride home tonight. The car was fully warmed up when I started recording.

Min Max
O2 1x1 0.02 0.95
O2 2x1 0.02 0.94

STFT1 -15.0 17.6
STFT2 -14.5 17.4

LTFT1 -7.0 10.0
LTFT2 -4.9 9.5

Nothing that looks too far out of whack. But, the car seems to be getting worse. Revved it up to 3500 RPM while in the driveway and it started misfiring. That was something new. Probably parking it at this point until I can get the LIM/UIM gaskets replaced. Then, I'll reassess.
 

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Owner of #RaceSable
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Killed a cat. I remember this issue being exactly like this on mine.
 

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Killed a cat. I remember this issue being exactly like this on mine.
Which one did you kill? Hard to figure out without dropping much of the front exhaust. Lots of rusty bolts. With my luck, it'll be the one on the backside of the engine.
 

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Owner of #RaceSable
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I think it was my 3rd cat. Remove the bank 2 lower 02 sensor is go for a rip and see if the power is back at all.
 

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Discussion Starter #7
I'll have to give that a try. But, it requires getting the car high enough into the air to get access to it. Also, as I get older, I'm less inclined to do things far under the car. But, the 3rd cat is the easier one to replace.
 

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BTDT on all accounts here :)

if you want to test the 3rd cat, open the downstream sensors. If you are testing the front cats, upstream. Unfortunately what happened with mine is the PO ran it way too long with a misfire(though they told me it wasn't) and it killed the rear bank cat. Broke the substrate and sent it down to the 3rd cat where it got stuck and killed the power.

If I were you, I'd get under the car and give a few taps on the 3rd cat with a rubber mallet to see if you hear anything loose in it. Then go from there.
 

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Discussion Starter #11
Thanks John. I'll give it a few taps tomorrow night.
 

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Discussion Starter #12
Well, I tapped around the exhaust a bit tonight. Right on the rear cat, it's hard to tell. Too many other rattles in the exhaust. On the pipe in front of the rear cat after the "Y", it does sound like there's something loose in there. On the front pipe, ahead of the "Y", it sounds clean.

So, my best guess is the cat on the backside of the engine failed and spewed it's remains into the exhaust clogging up the rear cat.
 

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Not a really great video but it's 6 years old. :D




I now know that when I tapped on the rear bank cat there was nothing in it and all that rattling is the substrate pushed to the rear cat. Does it sound like that?
 

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Discussion Starter #14
It doesn't sound that loose when I tap the cat. But, the pipe in front of the cat sounds more like that. Maybe not quite as much stuff. I'm dropping it off at the shop tomorrow to have them take a look.
 

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Discussion Starter #15 (Edited)
Got some good news and bad news from the shop. The good news is it's the rear cat that's plugged. The bad news is my car is a C.A.R.B. compliant car.

The cheap-azz side of me says to pull it off and punch it out. No emissions testing in my area, other than a CEL test. So, no issues there. But, the pipes into or out of the cat aren't straight. Might be more work than I want to do.

I did find a C.A.R.B cat on RA for $216. Better than the $600+ the local parts stores want.
 

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The question is what plugged it? If it is melted then ok it's from misfire but if not then it maybe the upstream cat breaking up. A non CARB cat is better that no cat.
 

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Discussion Starter #17
The question is what plugged it? If it is melted then ok it's from misfire but if not then it maybe the upstream cat breaking up. A non CARB cat is better that no cat.
The upstream cats were fine.
 

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cut the cat off, you don't need to pass any kind of emissions testing. no CEL will come on and the car will be fine. Oh and the throttle response will be better.
 

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Discussion Starter #19
Got the car back today after the second go-round on replacing the fuel injector seals. Don't appear to have any leaks. The leak was in the #1 and #4 injectors. After fixing those, the #6 started leaking. The mechanic was having a tough time getting everything lined up and put into place without damaging a seal. But, the 3rd time appears to have been the charm.

The car seems a lot peppier, from even before the cat melt down. Top end is a lot stronger. Makes me think the cat was slowly failing over time. They gave me my old cat back to recycle, might get $20 for it.
 

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Discussion Starter #20
As an indication of how bad it was, my mileage for the past 2 weeks was 17.8 MPG. That was about 2/3 of the miles with it blocked, 1/3 of the miles after being fixed. Normally, I'm 20-22, without any extended highway driving.

I have also noticed that the exhaust is louder now. The old cat must of muffled things down a bit.
 
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