Catalytic Converter

I’ve got a 2006 Nissan Frontier. Last winter I had to have the catalytic converter and O2 sensors replaced. Now its giving me troubles again. What could cause this to happen two years running. The first was under warrenty, but I’m not sure if this would would be or not. I’ve got about 58,000 miles on the truck

Is the catalytic converter giving you trouble, or the vehicle?

If its the cat, then yes, it would still be under warranty, as federal law mandates an 8 year, 80k mile warranty. As for why, well, that may be because something else is wrong with the engine and they didn’t properly diagnose it the first time. If, for example, a fuel injector is leaking, it could take out the catalytic converter… so by replacing it, they didn’t solve the problem, just a symptom. But there are numerous things that can damage a cat.

If its something else that’s giving you trouble, well, that’s just luck…

What are the “troubles”? We’re not mind readers here.

Thanks. The fuel mileadge has gotten worse lately and I’ve noticed the engine starting to stall out. It just started happening a couple days ago, but it turned into a major problem last year when I was out of town and I’m just hoping its not going to turn into a mess again.

If the engine is stalling, then it isn’t likely to be a catalytic converter, unless it is heavily plugged.

Is the check engine light on? Do you have trouble codes to help us out?

Stalling in and of itself may be a significant issue, but it can also be VERY simple and cheap… its hard to tell without more info…

You’re going to have to give us all of the information about the truck, not just little bits here and there.

How bad is the fuel economy?
What modifications have been made to the truck (big wheels, 10" lift kit, etc)?
How much oil does it burn every 1k miles?
When was the last time you had the spark plugs changed?
Do you have a misfire, and have you dried replacing it?
What codes are you getting from the Check Engine Light?


No engine light yet, but I’m pretty sure it’s not too far off. It’s pretty much the same symptoms I had last year when the c.c. went bad.

I’ve got a momentary loss of power at times when it gets to about 2-2,500 rpms. At first I thought it was my transmission slipping back a gear, but then realized that it was more an engine issue than a trans. issue. My fuel economy has gone from 21 mpg highway to 16-17. No modifications to truck since the last time it went bad. I had the spark plugs changed about a year and a half ago. So maybe 10-15,000 miles since they were replaced.

It is not likely to be a pollution control related problem and not trigger a code. However not ever mechanic is going to look to find out why there is a code and many will just keep replacing the same part when that part is the result of a defect not the cause.

I suspect something is making it run rich.

Do you by chance think it could be an ECM relay?

The ECM relay would make your truck to “no start” or to quit. We need some history on the truck, such as why did you have to replace the sensors and cat.
I would check the coolant level and temperature, as if your truck not entering into close loop due to a fault temp sensor. If you can rent a OBDII reader from autozone and get into “pending codes” and “live sensor readings” and put it here so we can take a look at it.
Good luck.

My theory:

Whatever is causing the vehicle to stall, lose power etc. is putting stress on the cat, by letting unburned fuel go out the exhaust.

Fix the drivability issues and the cat converter won’t be damaged.

Check for weak spark, compression, fuel pressure, clean MAF sensor & more.