I think one of my catylitic converters died

[Herz]

My 2002 GMC sierra soon approaching the 140k mile mark had some issues 5 miles from work.

It started back firing so I pulled over and checked the plugs, dist cap, rotor, cables, oil level was good, and all seemed fine and tight. I wated 5 minutes with the key turned but car off then restarted. Very rough Idle, low RPMs drives like [censored] hesitating and backfiring. Noticed a rattle from the floor of the cabin, tell tale sign of a cat. I was able to drive to work in low gear with high RPM. Car threw a CEL.

Would you guys replace both cats or just the bad one. I intend to disconnect the headers from the exhaust 1 by 1 to single it out tommorow as I have the day off.

 

[Summerwind]

MM, personaly, if you can afford to, I would replace both...The "good-one" can't be too-long for this world either I would guess....Sorry for your bad luck...

 

[Herz]

its all good, stuff is bound to break eventualy lol.

 

[JHZR2]

To me it depends upon how/if you are emission tested. If so, I'd probably do a good scrub of the system, replace both plus ox sensors.

If not, I'd just replace what was needed and go until you have another real issue. This stuff can be expensive, and I'd advise against the cheap generic cats - they are cheap for a reason, and it is because they are really poor at conversion...

 

[Bill in Utah]

What was the code thrown?

Unless the cat is plugged (which would have caused the truck to throw codes WAY before it starts to run poor) I doubt you running issue IS the cat.

Lets start at the code and see what it says. Then go down the list. BEFORE I started getting Cats, I'd MAKE SURE that IS the problem.

My truck ran fine just threw codes, once I did what JHZR2 suggested (replaced the post O2 sensor) the truck runs the same (excellent) but never saw the code again.

Keep us informed!

Bill

 

[ARCOgraphite]

I'm with Bill; also pretty sure that something else causing overly unburned fuel killed the cat - like a failed CPS or high tension ignition or T-Chain or loose TB or ?? You could put new cats and end up killing them in 1 day.

 

[StevieC]

I'm with Bill don't replace anything until properly diagnosed.

 

[440Magnum]

I would be AMAZED if it were a catalyst problem. They're blamed for everything from rough idle to jock itch, but they very rarely fail unless some other problem causes them to overheat.

The symptoms just don't fit, either. If a catcon were plugged, you would NOT be able to run in "low gear high RPM" as that is exactly the kind of condition where a plugged exhaust is most noticeable.

 

[bdcardinal]

What really sucks is being that the OP is in California he has to use OEM or CARB approved cats. We can't even get non OEM or CARB approved cats shipping into the state.

 

[ARCOgraphite]

Salvage parts?

 

[mechtech2]

The rattle was from rough running - misfiring. Who knows what was shaking.
There is no indication yet that this is a cat going bad .
Fuel and ignition are prime suspects.

 

[SAATR]

It's highly unlikely that a failed cat would cause such behavior. When a catalytic converter becomes "plugged" or "melted" it restricts exhaust flow, and causes the vehicle to not be able to rev very high, like a governor or rev limiter is being used. Restriction leads to increased pressure and heat, which leads to further failure of the catalyst. Eventually the car ceases to be able to run due to exhaust restriction, or blows a gasket or seal in the system to allow the pressure to escape.

The symptoms you describe sound more like a failing coil, failed FPR, huge vacuum leak, or a bad MAF. A scanner capable of reading live data would give you a much better idea of what is going on, so I would have it properly diagnosed before throwing parts at it.

 

[Chris142]

Originally Posted By: ARCOgraphite
Salvage parts?
He's in Ca. The replacement cat(s) must be new. Must be from the dealer or C.A.R.B approved.

 

[bdcardinal]

Originally Posted By: Chris142
Originally Posted By: ARCOgraphite
Salvage parts?
He's in Ca. The replacement cat(s) must be new. Must be from the dealer or C.A.R.B approved.


+1, the local salvage yards here told me it was a felony for the yard owner and a $10,000+ fine for selling used emissions components.

 

[Chris142]

Originally Posted By: bdcardinal


+1, the local salvage yards here told me it was a felony for the yard owner and a $10,000+ fine for selling used emissions components.
I don't think it's afelony. Misdemeaner with a fine and possible prison time though.

"Hey what you in for?" "Selling used cats".

 

[Herz]

I got the car at a mechanic to read the codes, dont have a OBD scanner. Will replace parts myself.

 

[Bill in Utah]

Be careful and don't just replace parts because they threw a code.

A lot of the time one part going bad will cause others to start to act up. Then they throw a code.

Get the codes and then go through the process before throwing parts at the vehicle.

 

[Gary Allan]

Quote:
T-Chain


This was my first thought.



..and AFAIK, there's no such thing as a legal used catalyst market anywhere in the USA. You may find one for sale, but not as an "intended for use" component.

 

[mechtech2]

Other hardened prisoners go really hard on new guys who are sent up for this. OUCH!

 

[Herz]

Random misfire code, mechanic did a compression test, fuel injector test, all checked out good. Discovered the distributor housing cracked causing timing to go out of whack.

Told me to replace plugs and cables since he found one plug cable was bad, and come back to reset code, he ziptied the distributor temporairly. He wants me to drive it for a day or two to check for any new codes.

I will have him replace distributor, cap and rotor.

I tossed some new NAPA belden wires, and AcDelco plats on it.

thanks for all your help guys.