Bat Man

What are the symptoms?
How hard is it to get the cat off?
Directions anyone? What exactly is in the tube that runs to the cat?
Anyone have any pictures of their clogged cat?

Springer's LT4

Symptoms include no power on acceleration, glowing red exhaust manifolds at night.

Don't forget you've got 2 pre-cats and one main in that car...

SLEV89

a clogged cat is like sticking a potato in the exhaust pipe (4 potatoes!)
the airflow can be severely restricted.
often the car idles fine, but as soon as a higher RPM is required (equals higher airflow) she'll poop out on you since she can't breathe :chevy

Bat Man

I was just wondering because lately, my car just feels like a dog. It won't spin tires straight up, Not even power braking it. :( I've never done a real burn out in it.

Lets say I'm on the high way at like 50mph in 3rd (auto tranny). I'll floor it the tranny will downshift throw me back in the seat, but it pulls SOOOO SLOW. It feels like its pointless to even go full throttle because half throttle feels like it pulls alot faster.

BobMachus

I'm right there with ya Old Sport. Same symptoms. I'm gonna remove my pre-cats next week. I'll get back to you guys about how that works out. I am also gonna put in new wires, new plugs, new cap and rotor, and maybe a Performance Distributors coil. I'm gonna find a way to light up those tires if it's the last thing I do.

Bob

ZylaRace

The 88 has a slip n converter, so it can be a bitch to get off the from Y. The small tube injects air from the engine air pump. You will probably have a crimp band holding in place. (You can't reuse it.) When off, an unclogged Verter can be seen through. (Light will pass from in to out,...)
The precats,... you can't get to them w/o cutting them open. If you do, just remove the contents. (They do very little, and add a lot of back pressure.)
Like they said, cherry red pipes, and no top end.

Bat Man

I hope you find the way. When you floor it what happens?

traxx1

There is a place called muffler tech in california that can sell you a test tube that is a direct bolt on in place of your cat, I believe there number is 1-877-722-3784 you might want to go this route.

:jester traxx1 :jester

ConeKLR

You will also get starter heat soak problems due the the exhaust heat buildup.
Do a top speed run, and then check the the temps in your engine bay. Also check frop starter heat soak. These are the issues my 91 had 2 months before the pre cats finally clogged my main cat. My new main cat also got clogged due to the final precats breaking up. Your precat/cats can be slightly clogged and the car can still do 125 mph.

Rick86

You can test the back pressure, before removing the cat. If you know of a muffler shop that you can trust they will test the back pressure for you and tell you if you need a cat. Less than 3 psi at 2000 rpm is considered good. If you are inclined to do the work yourself here is what I rigged up. You'll need a fuel pressure gauge capable of reading 0-10 psi, then buy a hose designed to hold pressure in the cylinders, so valve springs can be changed (I bought this hose at Kragen for about $10.00), the hose should come with a 14mm and 18mm threaded end, this is the same size as the O2 sensor, so once you hook up the hose to the pressure gage, unscrew the 02 sensor and replace with the hose, then measure the back pressure, mine was about 1 psi with precats, main cat and dynomax mufflers. Good luck

C4 4Me

In my old 88 Fiero back in the early nineties one day I was driving along, hit the gas and acceleration was like a snail and I couldn't get the car over 40MPH and it got significantly quieter.

No symptoms at all prior to this, it just happened that fast.

B R

You would probably notice a drop in your MPG if you normally keep track of that as well as higher than normal engine temps. It did take some beating & a good vise to get the main cat off the front Y pipe. :smash:

SunCr

From GM Service Bulletin ATRATB028, 10/1/90, connect a vacuum gauge (PCV line is a good source of manifold vacuum). Note idle vacuum (it should be steady between 14" and 22" HG). Slowly increase engine speed to 3000 RPM.
Vacuum should be equal to or higher than idle vacuum. If not, an excessive exhaust back pressure is present.

GiDvEtTe84

My cat was pretty clogged. I had it replaced with a straight 4" pipe. I got back at least 20 or 30 hp. Car also sounds like a dream!!!!!! :yesnod:

pablocruise

BobMachus, watch out for the "accel" brand cap. I had bad luck with that one. One of the brass posts became severly corroded even though the plug wire was on tight. The center also melted ( I think there was an explosion in there). Bought an MSD red cap but the hold-downs were "L" 's and not screw in. Modified the cap no problem. Ft. Collins? I had a good experience with The Vette Shoppe. Awright gidvet! I understand a vette will still pass tailpipe test even w/o the cat. Good move. I wish I had done that when my cat clogged. Floor it and help remove those carbon deposits! :D

BobMachus

Old Sport,

When I stand on the gas it goes, just not quite like a Vette should. Just kinda squats and meanders off the line. At about 2000 rpm it gets a little more, kinda like a small NO2 shot or a turbocoming on, but only pulls hard to about 3000, then bogs again. MPG around 17. It was rainy the other nite, and even with wet (but not soaked) roads I could only spin my tires for about 3 seconds! Any tips? The main cat was new about 1 1/2 years ago, and would be a pain to remove (already tried), so I am gonna start with the pre-cats. Later guys, gotta go to work for a while.

Bob

O'Shark

You'll get just a whisper from the exhaust. My car even pinged with premium fuel in the tank. I could also here a sound like air escaping under the hood. It's hard to explain.

The slip on converter is a pain to get off unless you have tools. I used the appropriate tip on an air hammer and it came right off.

Randy

phrogs

My main cat got cloged by insulation and chunks of the honey comb stuff from the precats and it was totaly cloged my car had no power at all it would idle and t sounded like I had a major air leak up front it was the exhaust pushing out through the manifolds :eek: If i steped on the gas the car would bog down and die I removed the exhaust and cut off the front y-pipe and I found my problem replaced the front y-pipe and put a slip on cat from mad and I had my flowaster cat back on so now im styling, I was so glad to fianlly find my problem It caused me to warp my passenger side head :U
but she is good to go now :cheers:
It dosnt sound like your is anywhere near as bad as mine...
good luck


[Modified by phrogs, 9:38 AM 8/22/2001]

91Vette

My 91 is in the same club. It seems to be down on power. When I punch it, it feels like there is some type of restriction holding it back. I've called a few muffler shops and no one will test exhaust backpressure. I might try the vacuum gauge test (from above) or take it to the dealership.

ZylaRace

The vacuum test is easy to do. Vac gauge is ~15$ Ports on the pass side of the plenum.

From your other post, it still seems like something is tired. Do you have an AFPR on it?