01 catalytic difference? code (loss of power/loud exhaust)

[Cool D]

Hello.

I recently have lost a ton of power in my 01 Grand AM 2.4L. Basically runs fine on flat/downhill runs, but at higher speeds (45 and up) there is little and sometimes NO power going on up-hill highway inclines. The car chugges and when trying to accelerate there is a loud exhaust problem like sound seemingly right below me and/or directly under the engine.

Autozone checked the codes and told me it had a two codes come up. Sorry for the non mechanical language but at Stage 1 it read a catalytic differency and Stage 2 the same thing. (catalytic different something anyways)

I would rather try and work on this car on my own if possible. It's a second car and don't want to stick much cash into it.

I've changed my oil, oil filter, spark plugs, and air filter. I did follow the air filter to the "box" over the air intake and removed it and then noticed a small hose next to the air intake leading downward on the engine had a bunch of yellow "sludge" build up. What is this, and could this be the problem?

Please help if possible. Thanks!

[Madcat455]

Sounds like a Cat. Converter to me.... I'm having touble picturing the hose that has the gunk. Does it attach to the air cleaner box?? and where does it go into the engine?

It could be the crankcase breather, in wich the gunk wouldn't be a big issue. (I thought the breather tube attached to the intake hose, not the air box... but I can't rember for sure).

[Cool D]

Madcat455, yes the host attaches to the air cleaner box. One side of that box has the large hose going to the air filter and the other side has two hoses; a large hose going to the intake valve? and this small hose leading downward.

I have read many other posts and some say change the front O2 sensor. I'm just trying to keep costs down if you have any ideas, so un-needed replacements are trying to be prevented.

Also, it looks like black type "soot" stuff in scattered throughout the engine in many places that i've never noticed before.

Is there a way to "clean" the exhaust system myself. I know w/ a carbutrator engine we used to, but this is obviously different.

[Scanner]

Try a fuel filter.
If the exhaust leak is any where near the cat it will cause those codes.
You can ck the cat simply buy removing the O2 in front of the cat, drive the car and see if that makes the problem go away.

[Cool D]

Scanner,

I did have to replace the fuel filter and the fuel pump last year. Is that something that could still need replaced in only a year. I do have an extra fuel filter I bought back then so it won't hurt to try. Thanks!

Would the "loud" muffler type noise when accelerating be somthing different w/ the exhaust do you think?

Thanks again.

[Madcat455]

Since the exhaust comes off the back of the engine, if there were a leak there then you could be getting carbon deposits in the engine compartment.

Your exhaust leak could be caused by a couple of things:

1: Hole in a pipe (most obviously), would cause loud noise, and fumes (plus deposits).

2: Plugged Cat. Converter building excessive back pressure in exhaust system, causing it to blow by the gaskets. Manifold gasket, donut gasket where the down pipe bolts up to the manifold. Will also cause loud noise and fumes with deposits. Will also more noticably cause very poor performance. I had a cat plug up on me and the car performed fine up untill 60mph... would hold speed with normal throttle but if I tried to increase speed, it would get really loud and would not go anywhere even at WOT. Also noticed excessive heat... more than normal.

3: Just plain ol' bad gaskets... unlikley but possible


both 1 & 3 will only cause a couple of symptoms... loud noise, computer codes, and fumes/heat. but no performance loss (hell, sometimes you get a performance GAIN from the lowered backpressure)

#2 will cause all the symptoms, unlike basically any other "single" problem that can occur. Age and Milage mean nothing as my Wifes Cat just had to be replaced on an 03 with only 25000 mi. So anything is possilble.

If you're looking for a cheap way to test my theory... jack up the front of the car, unbolt the exhaust system at the manifold (basically only 2 or 3 bolts)... then tie the pipe up with a wire coat hanger, keeping it away from the mainfold or any heat source.

Drive the car... it'll be louder than a bitch, smell the same (make sure you roll with the windows down). If the speed problem dissapears, then you know the culprit is the cat.

just try not to get pulled over...lol.


Now you could be having multiple things happening that will cause all the symptoms, but other codes would be present... not just the exhaust codes.

Good Luck

[Cool D]

WOW, that is a GREAT reply.

Thanks a ton! I will get back to you with my findings.

Thank you so far.

[Scanner]

removing the 02 (oxygen sensor) in front of the cat, is a lot easier than unbolting the exhaust, the purpose is to see if when you remove the 02, it relieves the excessive back press. that may be cause by a plugged cat.

If you replaced the fuel filter just last year , chances are it's not your problem now.

The cat efficiency is determined by comparing the front 02 reading with the rear 02 reading, if the cat is plugged it could give you this code...however...if you have a exhaust leak anywhere near the cat, the oxygen that is getting in the exhaust near the sensor, could then cause a false reading..setting the code.

Also.. either of the 02's not responding as fast as the other...could also set the code.