Has this happened to anyone else?

[MWM]

I'm baffled. I was driving home from work today and my truck was sputtering and sounded like the exhaust had come off at the header. Super loud and backfiring under the truck. It had no power and I could barely get it up to highway speed to get home. 2005 QC with a new transmission.

So I just crawled under it and the exhaust is tight. No holes and bolted in tight. Stock up to the cats and Borla cat back system. So I get in to drive it and it starts up, runs smooth, and has no noise.

What the heck happened earlier then? I know I'm not driving Christine and she magically fixed herself. I've had exhausts come loose and it sounded exactly like that but it's bolted up tight and welded well as far as I can tell. I'm going to keep driving and see what happens thanks to the extended warranty, but I don't even know what to check.

Do any of you more tech savvy guys have a guess? So weird. Thanks in advance.

 

[Django]

New one on me, bro.....

D

 

[jsandlin]

maybe one of your cats is clogged. Had that problem and it sounded like shti! Wouldnt get up to speed at all. Limped into the dealership.

 

[MWM]

Great call. It started acting up again so I ran straight to the dealership. They were looking at it and then began reving it and small chuncks of stuff were coming out of the exhaust. They took the exhaust off later and said one of the cats was destroyed. That's never happened before. But leave it to the Doc to diagnose me.

 

[TNVIPER]

Your next issue to resolve is why the cat did that...may be just a bad cat or you may have A/F problems....:dontknow:


Catalytic Converter Failure

Catalytic converter failures typically fall into one of four categories:
1. Thermal failure (overheating)
2. Plugged substrate
3. Thermal shock
4. Physical damage
Thermal failure is most often caused when excessive raw fuel comes into contact with the catalyst, and "burns" in the converter instead of in the engine. The high quantity of fuel generates temperatures well in excess of the capacity of the converter, causing meltdown of the ceramic monolith. The melted ceramic could block the exhaust path, leading to a significant loss of engine power. Visible symptoms include heat-related discoloration of the converter shell.
Potential causes of thermal failure include: misfire, malfunctioning oxygen sensor, fuel delivery issue, improper choke setting/operation, and ECU malfunction.
A plugged or contaminated substrate can be the result of an overly rich air/fuel mixture, radiator sealant, and oil or antifreeze entering the exhaust flow. The resultant carbon deposits restrict the operation - and ultimately the flow characteristics - of the converter by coating the unit's reactive surface. This degrades the converter's ability to perform its chemical conversion process, leading to potentially illegal levels of HC, CO, and NOx.
Root causes of this problem are a malfunctioning O2 sensor, plugged or inoperable fuel injectors, piston blow-by, leaking head gasket, broken or frozen choke or carburetor float, excessive cranking time, and repeated incidences of running out of gas.
Thermal shock occurs when a fully heated converter suddenly is "cold-quenched," such as coming into contact with snqw or ice. This leads to sudden contraction of the converter housing, which can cause cracks and disintegration of the ceramic substrate. Symptoms include a "rattling'' sound when the converter is tapped with a fist or mallet (monolith-type converters only).
Physical damage, caused by running over road debris, collisions and other impacts, is usually easy to diagnose. This type of damage can break up the ceramic substrate or cause restriction that changes the flow characteristics of the converter or impacts the efficiency of the catalyst.

 

[rottenronnie]

Good info TN...

One more to add to the causes of failure lists- Burning Leaded Race Fuels.
I don't know if he did that or not....but it will ruin them.

Ronnie

 

[MWM]

Awesome information. No race fuel or anything abusive. Just the 93 octane SCT tune which helped the transmission shell out a couple months back. 50k miles with no problems up to now. That 7/70 extended warranty is the best money ever spent. Thanks for all the great info guys!

 

[Begood]

I don't know the laws in your state, but I just removed my cats to be done with them.

Bill.

 

[mauiSRT/10]

Clogged cats have been a problem for these trucks..........another reason why so many of us have deleted them!

Glad you got it figured out.

patrick