Engine has to start for the PCM to care...... and it can't tell if the cat is clogging or not. It just looks at 'cat efficiency' (which goes up as the cat clogs, as there is less flowing thru it..... of course, the engine runs like crap.....)

Pull the Pre-Cat O2 sensor, see if it will start.

 

Sorry I guess I mis-worded that. Should the CEL have come on 'before' it totally clogged? This happened like a month ago..I already pulled the old cat and replaced it..And yeah, I did take the upstream O2 out and it still didn't start..That's what lead to me doing the plenum job...

 

Definite Maybe... I have seen many a melted down cat, and folks never had a clue what was going on. The PCM was getting data that it liked, even though it was wrong..... that caused the cat to overheat and melt. (bad O2 sensor.....)

Many things can kill the cat, not all of them, or even most, for that matter, will set a code.

 

Thanks HY, I did replace the upstream sensor (denso) and will replace the downstream soon! Have you heard anything about the bad cat doing damage to the muffler too? Thanks again...

 

Only if it blows out crap, and it gets lodged in the muffler. Rare, but, it happens. If most of the 'stuff' was still in your cat, probably not a problem. If you get good flow out the exhaust, I wouldn't worry about it.

 

Well, a bad cat will turn on the CEL and set a DTC about half the time. As for stuff getting in the muffler, often times it will blow out over time (unless it is an awful lot). Turns out It's Me Patt, that my main crank bearings might be going out instead of the oil pump. A friend is going to check it out and tell me a little more. Anyone else on this?

 

Ha, (it just) Patt When I was looking into pump failure I learned that pump issues/lube systems can be the cause of bearing damage/failure...and not sure about your year but mine requires the exhaust pipe to be removed/move (my entire system is all one piece from the EM's to the tips) and for the engine to be raised some, for oil pan removal (to replace the oil pump) So much for a simple job Post up the results your findings..

 

If you don't mind then I will just call you Patt... Some forums I have been on only allow the use of nicknames.... To replace the crank bearings I would have to remove the engine. And yes the oil pump going out would cause bearing problems. I didn't think of that at first. For me since I have 4wd high-clearance I can just pull the oil pan straight down, no hassle with the exhaust.

 

Hello, I recently cut off everything and am running open headers, I left the pre-cat O2 in tact and blew a CEL at start up, most likely you will get the same thing if you run straight pipes. As for the non-fouler trick, where would you put it if you chose run open headers? The computer is making her run rich and my mileage is down to 7-8MPG. I know there is a O2 simulator which fools your computer into thinking you have a very efficient cat installed, and you can buy from fastman. I contacted him and he told me he hasn't had them for a few months and doesn't know when/if they will be in. Any ideas where else they can be had or what I can do with the non-fouler?

 

Of course man! Your lucky with the clearance issue, mine has 4x4 but low clearance tho..You do regular oil changes? Is the oil really dirty when you do? Just wondering cuz dirt and/or dirty oil is also a known culprit for bearing damage/failure..hope that's not the issue and it's the pump or something...