This is just a theory, but, since there are no sensors after (past) the main catalytic converter wouldn't it be entirely possible that if it failed, there would be very little chance that the ECU even knew that the main cat. failed? I know on my '99 there used to be an O2 sensor right behind the main cat. which seems to suggest that it would somehow know whether that last cat. was working properly or not. This is why I'm guessing/theorizing that it's my main cat. Did replacing your pre-cat. entirely fix your problem with the power loss?

 

02SE6MT: Did you get any codes that suggested what the problem was when your pre-cats fell apart?

 

I'm going to have to say it again.... haha

Gut the cats or install H/Y. If you want to kill your engine (directed at everybody) by all means keep the cats in there. It's a ticking time bomb. You're lucky you have symptoms. Do not drive it unless you want to junk the motor.

 

 

I won't say it 100% solved the power loss problem but it's a step in the right direction.

First I had rear oxygen sensor codes along with the "rattle" sound produced from revving the engine in park or neutral. Got the oxygen sensors replaced, then got the P0420 code. I also switched from 87 octane to 91 or better which did help the "pinging" hesitation problem. Plus I installed a used MAF, installed a new fuel filter. Dave B the parts guy said don't waste time replace the bank 1 pre-cat. Taking his word I spent the cash and got the pre-cat replaced.

I can say the engine feels better than it did before. Long story short? Pay a shop to pull the cats and inspect them. You'll have to replace gaskets but at least you'll know if you need to replace a cat.

 

The ECU would have no idea the main cat was bad. When I replaced the precats on my car with much lower mileage ones, I also replaced the main cat with a Warpspeed test pipe. Between newer precats, a test pipe and an NWP block plate, my 45-85 times dropped over 2 seconds.

I wasn't having the severe pinging or rattling and my car would pull clean to redline (was getting a P0420 code and the precats were showing some deterioration but not that bad) but it felt a bit down on power.

 

Just another update, I replaced both valve covers and replaced the copper plugs for Iridium IX plugs. I do feel a bit more power but, as best as I can describe it there still is some feeling of power loss.

Consider this, accelerating toward a left hand turn onto a freeway on ramp. Once you approach the turn, as I turn in I'll sometimes back off the accelerator to make the turn. Then as I end the turn I'll press the accelerator to pick up speed. However I feel the engine has almost no power, as though no fuel or enough air is making its way to the cylinders. If I back off the accelerator and very very lightly press down, I can gain speed. But, it’s not as it used to be. Where I could gain speed very easily.

That is as best as I can describe it.

I'm thinking about the fuel pump or throttle body. MAF is a 2000 maf with the 2002 IAT wire soldered in.

Thoughts?

 

Last update, replaced the bank 2 pre-cat (had the MIL on for it) and now the engine feels better.

 

Hey, I should have posted this a long time ago, but since the thread was revived... here's what I actually did to fix the problem I wrote about from above. It was kinda easy, cause the rattling was most notable at the main cat, I took it apart. It was clogged and cracked. Like I had described before, major power loss around 3-4k. Well it let just enough air through to idle, but not perform normally. So, I completely gutted out the main cat, and put it back. No more power loss. My exhaust is kinda loud, but that's expected, when you have no main cat, and the cat back pipe is pretty much straight through. Just my 2 cents bro, might want to check that main cat. For me it was a clear as daylight difference before and after.

 

Thank you for the tip, if I do replace the main cat I am going the cheap aftermarket route.