Pardon me VW, but why can't you run the rear O2 until it quits? As long as it doesn't pop a code, why replace it? All it does is tell the PCM if the catalytic converter is OK.

However, I do agree with you on the front (pre-cat) O2 sensor. That one is much more important.

 

the 02 sensor was replaced probably 3000-5000 miles ago...did it myself. none of that is the issue really. i'm pretty sure its the CAT for loss of power. as far as clunking goes, well thats another story lol

 

does your state require emissions testing? if not then i wouldnt even put a cat on it.....you dont have a rear o2 sensor so no isssues there

 

I've noticed, over the years, that O2 sensors don't always "go bad". They can slowly degrade in their ability to work and not throw a code. Hence why many a person's cat will get plugged. Now, I realize that these trucks came with faulty cats from the factory, but I look at replacing the O2 sensors as a pair, at scheduled intervals, as preventive maintenance.

 

Just throwing **** into the wind here (don't know why i said that. It just sounds funny i guess. Its early for me lol)

Could the hissing be some kinda vac hose or something going to the tranny? Then it would be one problem.

 

we dont have a vac line like older vehicles....good guess tho

 

well, i do have to get a new cat because my state DOES require emissions testing. and as far as the hissing, it was exhaust related. i'm not too worried about it. this weekend i'm gutting it because my inspection is up this month and i know it wont pass anyway. so it'll give me and excuse to tell my wife i need to spend money on the truck

 

do they use a sniffer or just look for a cat?

 

Wjxavier, I believe you hit the nail on the head, as I had a similar occurrance on one of the Taxis I used to wrench on when I worked at Happy Trails. It sounds like a piece of your catalyst broke off and was causing a restriction, then broke into smaller peices and was expelled. As far as the clunking when accelerating/ engine braking, that sounds like a u joint going out. Get under there and check your u joints.

 

yea i know my ujoints are bad...theres a lot of stuff bad on my truck, i just havent had a place to fix everything yet. my wife and i finally moved into a house with a nice garage i can work on my truck in im a happy guy.

and yes, they do use a sniffer for emissions inspections.