How to tell if cat is clogged?
09-14-2006, 01:47 AM
#1
Racer
Thread Starter
How to tell if cat is clogged?
Just bought an 88 Carrera w/ 119.000 miles. Any suggestions as to how I can check if the catalytic converter is clogged, and if it is (which presumably is the case), how badly it is clogged? Thanks in advance!
09-14-2006, 08:19 AM
#2
Legacy Flounder
Rennlist Member
Rennlist Member
Join Date: Nov 2004
Location: Cumberland, RI
Posts: 3,439
Likes: 0
Received 0 Likes
on
0 Posts
Does the car run, run badly? If you disconnect the cat from the crossover pipe, does it get better? I'm sure there is a more formal approach. I've had 2 (non p-car) cars that had plugged exhaust / bad cats... 1 as you drove it got sluggish, more gas you gave it worse it got, other was non-running on purchase & would sometimes catch while starting & then immediately shut down. Disconnected the cat-back & found half the brick had broken & been jammed at the bottom of the Y, choking the exhaust off.
09-14-2006, 10:53 AM
#3
Addict
Rennlist Member
Rennlist Member
Join Date: Aug 2003
Location: Raleigh, NC & North Myrtle Beach, SC
Posts: 4,146
Likes: 0
Received 2 Likes
on
2 Posts
One way to tell is if the car is exhausting through the air cleaner. Check the air cleranere. if it is real dirty, chances are the cat is clogged. this has been the case on other cars i have seen. Never seen on a 911 though.
09-14-2006, 12:08 PM
#4
Pro
Join Date: Jun 2001
Location: Oak Park, CA
Posts: 580
Likes: 0
Received 0 Likes
on
0 Posts
I had someone give me an old English sports car for free once. It was in nice shape but he couldn't get it running after 100s of attempts of finding the problem. It spent years in his mom's garage and finally it had to go. It was free to whomever could tow it away first. I was the lucky taker. But, actually at the time, I needed another car like, as they say, a hole in the head. So, I actually gave it to my brother in law. It sat in his RV spot for about a week before he showed up at my house driving it with a big grin on his face. What was the problem (if you haven't guessed yet)? The muffler had collapsed inside and was completely blocking the exhaust. To this day, I have no idea how he thought of it. But, he got under the car, punctured some holes in the pipe forward of the muffler and it started right up!
He still has it (and the "seller" didn't want it back).
He still has it (and the "seller" didn't want it back).
09-15-2006, 01:21 AM
#5
Three Wheelin'
If you don't want to get dirty from crawling under the car and disconnecting your cat, an even quicker test is to hook up a vacuum gauge to a manifold vacuum source. If everything's ok your car should be at about 16-22" vacuum at idle. Snap the throttle open real quick, say to 2000-2500 RPMs and then let go. Normally this will cause the vacuum to drop real quick, but it should also return to normal vacuum at idle quickly as well. On a car w/ restricted exhaust, the needle will rise back real slowly after you let off the throttle, and often to a lower level than normal. Hope this helps!
---
Chris Andropoulos
Schneider Autohaus
Santa Barbara, CA
---
Chris Andropoulos
Schneider Autohaus
Santa Barbara, CA
09-20-2006, 10:42 PM
#7
Intermediate
Join Date: Dec 2003
Location: Los Angeles
Posts: 38
Likes: 0
Received 0 Likes
on
0 Posts
Clean out the cat, even if it does not need it. I did mine (actually my mechanic did) and it sounds great. Symptoms were lack of power, especially noticible off the line and uphill. Did not notice any change in the sound until it was cleaned out.
Trending Topics
09-22-2006, 12:49 AM
#14
Three Wheelin'
Yeah gutting a cat is of course totally illegal, but I have seen quite a few customer cars, both 911SCs and Carrera 3.2s pass smog w/out a cat (not OFFICIALLY, but the emissions numbers were low enough to be able to pass the real thing). The engine has to be in really good shape and running perfectly however. But we are in Santa Barbara and thu only have to pass a Basic smog test which measures at idle and 2500 RPM in neutral. Enhanced could be different, but I have heard from guys who have shops in enhanced areas that 911s are so efficient under load that they are still OK if all is well. Mind you I am NOT condoning this practice, of course. On an NA car the performance gain for gutting a cat is minimal at best; only on turbo cars does it make a significant difference.
---
Chris Andropoulos
Schneider Autohaus
Santa Barbara, CA
---
Chris Andropoulos
Schneider Autohaus
Santa Barbara, CA
