How can you tell if your cat is stopped up or restricted? I have put a pyro on it and it is actually cooler than the rest of the exhaust. Is there another way?

 

When my cat was going south, I was having driveability problems. On the freeway, my car didn't want to go past say 60mph(when I knew it could). If I tried to go faster, the car would hesitate and jerk front and back like it ran out of power. After a while, I couldn't go past 50mph, then 45 and so forth. The car would die after a while of driving but then started up after I waited for a while. Then the car left me stranded and wouldn't start up. I would turn the key and nothing(no starter movement, but all of the electricals worked. Another sign is if your cat is glowing orange(not a good thing with carpeting only inches away). I've seen that happen once, on a different car. Those are two signs that I know of. On my camaro I had the bucking and the loss of mph, but not the orange glow. Hope I've been of some help.

[This message has been edited by coach (edited July 17, 2001).]

 

I was wondering this too..My cat has hit about 500 speed bumps in it's day.. It's also had about 3 gallons of oil burn on top of it..Should I be concerned? Could it be slightly clogged? Just enough to make me run 2 MPH slower? Cause that's what my car feels like..2 MPH too slow.. Thanks alot

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• Red '88 IROC 305 TPI T-5 w/3.08
• Accel 300+ Ignition
• Accel 300+ Pro Sleeve Plug Wires
• AC Delco Rapid Fire Plugs
• Dual Friction Stage III Centerforce Clutch
• Energy Suspension Transmission Mount
• Flowmaster Force II 3 Chamber Cat Back Exhaust
• Gutted Airboxes
• Hypertech Stage II PROM
• Hypertech Airfoil
• Throttle Body Coolant Bypass
• Best Maryland (40 degrees) E/T 14.686, 60' 2.205, 1/8th mile 9.461, 1/4 mile MPH 93.91
• Best Florida (80 degrees) E/T 14.88, 60' 2.163, 1/8th mile 9.540, 1/4 mile MPH 92.74
• Best 60' 2.163(Florida)
• TPiS AFPR set to 42psi using Accel Fuel Pressure Gauge (Installed after Maryland run)
• Aluminum Driveshaft (Installed after Maryland run)

I am looking to buy Edelbrock T.E.S. headers with the y-pipe. I am also looking for a 3.42 - 3.55 posi disc rear. cheesy@fred.net is my e-mail, send a letter if you can help!

 

Put the car up on jack stands and gently beat on the cat with a rubber mallet or something similiar. If you can hear rattling inside then the cat is dead.
bsa

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"If they do not run, Then they will die." - Stonewall Jackson
#3
'87 IROC, 355 TPI, Converted to SD, 700R4, B&M Megashifter, 3.42, Trick Flow Twisted Wedge Heads, Edelbrock Intake, Accel Runners, Comp Cam, Crane Gold rockers, Lucas 24# injectors, Edelbrock headers, Flowmaster 3'' exhaust, Mallory Ignition, Transgo Performance Shift Kit, Corvette Servo, 2,000 Stall Torque Converter

 

If your worried do as I did, take it off, get a brrom stick and pound all the crap out... Make sure it is empty and toss it back on... Save up then buy a new high flow converter..

 

Two ways to check for restricted exhaust.

Backpressure test, monitor through the O2 sensor hole, or the top of the AIR tubes off the exhaust. at 3000rpms the pressure should not exceed 3psi (GM spec).FYI, my back pressure is about 1.25psi.

The other is to monitor the intake vacuum at idle, stock engine in decent shape and tune, should be about 18-20 in/HG, increase the RPMs (park/nuetral) to 3000 or so and watch the gauge, if it falls below the intake reading by more than 2in/hg, indicates exhaust restriction.

The inexpesive fuel pressure/vac gauge combos work great for this, FP goes to 20psi, and has apretty good resolution.

 

Bad mileage can be a sign of a bad cat. When my cat was plugged up I was getting 6mpg city and 10mpg highway. After removing the cat and replacing the muffler I get 16 city and 24 highway. But my muffler was all rusted out inside so it was probably adding to the restriction.