Cat Questions

[Devon]

My cars been reading 420 cat efic below threshold bank 1, and idle control system

First I was told it was the 02 sensor before the cat, Evergreen said I need to replace the cat... and that will throw both the codes

I've been told it may be clogged and I can just "punch it out"

or I could buy an aftermarket cat for a lot cheaper. (but I also read that its a waste of money)

Butttt, It just sounds like I have an exhaust leak near the cat. Would that trigger both codes?

Is there anywhere I can go that can tell me what EXACTLY is wrong for a small little fee?

 

[Matt]

the exhaust leak will cause that code, po420.....I don't remember the other code being there last time I saw it.....but it does have the header which ive been told can also cause codes....youll get charged a diag fee to look at it.....price determined by shop unless someone else can fix it.

 

[Devon]

Thanks, and yeah it just popped up last week. Idle control system malfunction** whenever I start my car it will rev up to three rpms then it will bounce around a bit between 2 and 1.

And what about my headers? Is there something wrong with them?

 

[Matt]

the increased flow can mess with the 02 and cats from what I heard......whats the other code?

 

[inski]

Sounds like 2 separate issues now.

(1).The exhaust leak can cause a cat malfunction, find out if the leak is before or after your cat-converter. If the leak is after teh cat then its most likely your cat is bad. If the leak is before the cat you'll need to fix the leak before the cat can be deemed bad.

(2). The idle control system is completely different that the cat system. The idle control problem is an independent problem. If you are not in Cumberland County don't worry about the cat issue unless you are experiencing SEVERE lack of power problems. The big problem right now is your goofy idle. If it shoots up to 3k rpms, and wonders above 1k rpms continuously then you may have a vacuum leak or idle air control motor problem, or someone has messed with you idle stop screw.

The cat issue really doesn't effect performance or MPG, but your idle problem effects both performance and MPG. that's why I would fix that first. Subaru cats rarely clog up effecting driving performance, they just become inefficient at breaking down the harsh chemical they are designed to break down. Punching it out wont make the light go out. It is possible the rear O2 sensor is causing the P0420 but unlikely. 95% of the time the cat has failed in a p0420 situation on Subarus.