Collapsed Catalytic Converter

[Corvette Owner]

My 2001 Chevy Impala had a collapsed catalytic converter. Performance was terrible, no pickup and severe missing after 3,000 RPMs. Also poor under load (wouldn't go up hills over 20-30 mph).

Took the auto shop a while to find this out, they suspected electrical due to code thrown (multiple cylinder misfires). When they checked back pressure, it went off the scale!

I never suspected this.

 

[Mr Nice]

How many miles does the car have ?

 

[beast3300]

Extremely common on the 01-02 W-body. Glad you got it fixed!

 

[Jakegday]

if your 01 3.8L has less then 130,000 miles, a GM dealership would have fixed it for free

 

[MrCritical]

Special policy I don't know about?

 

[Sayjac]

Glad you found the issue, and it wasn't too major a fix.

Based on my latest experience, relatively speaking, I'm thinking your lucky. But then, what you describe is what should happen when a cat goes bad, not total engine failure.

 

[Jakegday]

Originally Posted By: MrCritical
Special policy I don't know about?

apparently


http://www.grandprixforums.net/l36-catalytic-converter-warranty-11743.html
i stand corrected, i meant 120,000 miles

 

[Corvette Owner]

Originally Posted By: LT4 Vette
How many miles does the car have ?


The car has 122,000+ miles. From the "extended warranty policy", they say they will only replace through 120,000 miles, bummer.

But I didn't know about this anyway. You guys are knowledgeable !

 

[mechtech2]

A plugged converter [or one with a piece that randomly blocks flow] can be tough to diagnose.

 

[MrCritical]

Originally Posted By: mechtech2
A plugged converter [or one with a piece that randomly blocks flow] can be tough to diagnose.


And if it's "plugged" due to oil contamination, or engine missfire, it wouldn't qualify.

 

[ARB1977]

How could one test if a cat is clogged?

 

[Kestas]

I usually get on the ground and shake or kick the converter. If it's rattling, then the monolith is breaking up and some of the pieces may be lodged sideways, blocking exhaust flow.

 

[punisher]

Easiest/quickest test is with a vacuum gauge. When the engine bogs, the manifold vac will be near "0". Clogged cats can be a pain to diag as they don't occur too often, and their symptoms mimic a bad MAF, or fuel delivery concern (lean bog).

I remember my first diag on a clogged cat. I was still with an independant then, and I got a late 70s/early 80s GM full size. Took it around the block and thought "bad carb (Qjet)/clogged fuel filter/bad pump/stuck choke plate". Checked them all, no dice. I had the air cleaner off and I was getting another tech to rev the engine and I noticed a lot of fuel shooting out of the carb and actually getting the underside of the hood wet with gas. It clicked then, the reversion was kicking fuel back out the carb throat. Took the cat loose and it ran fine.

 

[beast3300]

Originally Posted By: ARB1977
How could one test if a cat is clogged?


1. The inlet of the cat is hotter than the outlet.

2. The cat glows red after driving.

3. Provide an alternate flow for exhaust. If possible unbolt something before the cat so the exhaust can escape.

4. Parachute/drag feel above 3,000-3500 rpms in any gear.

 

[eljefino]

When mine went out there was a mild rattle, a heat shield type noise, and a "slice of apple" chunk of honeycomb blocking the outlet. Most telling was the noise, it was kind of a muffled "ugh" at full throttle. The car's a stick shift so I could feel a little more engine braking too.

There was nothing I could do for more power and was taking hills in 2nd gear. But I could nurse it up to highway speeds if I waited long enough. The collapse was more or less instant.

The typical diagnosis is to pull the front o2 sensor and see if it runs better. Of course you have scalding hot exhaust hitting something under your hood so keep it brief.