Aftermarket cat for a 2001 Forester

[nitroman58]

After dodging the issue of the P0420 code for about 8 months, my son's car really starting to run terribly.

I wanted to find out if there are any aftermarket catalytic converters that someone would recommend.

I want to get another 2 years out of this car. I have heard from one mechanic that the aftermarket converters are junk. It would be hard to justify spending the money on the Subaru brand, since his car is probably worth that amount. The car is not running well at this point, so I have to make a decision this week.

[nipper]

Eastern brands are the cheapest and junkiest.

 

How many miles?

 

It may just need an O2 sensor and a tuneup. Dont jump to expensive conclusions as cats dont usually fail on these cars. 

[DaveT]

I used an aftermarket cat on our 2001.  Ran fine, lasted long enough.  Unfortunately, long ago enough that I have no idea what brand.  But most likely, not the cheapest - I don't buy solely by price.

 

Cats failing don't usually cause crappy running, unless the failure mode is that it is clogged up, which usually indicates something else is wrong, overloading the cat.

 

A way you can test for flow - loosen the nuts that hold the Y pipe to the exhaust ports.  [beware if these have never been touched, and everything is all rusted up]  [mine get antisiezed and are easily removed for such checks]

 

Drop the Y pipe enough to have a 1/2" gap between the block and the flanges.  Get a vacuum cleaner, with a hose, and arrange things so you can connect it to the outlet of the exhaust pipe.   The idea is so that you can connect and disconnect quickly.  Listen for the pitch of the vacuum cleaner's motor.  It should only change a slight bit higher, if at all, between disconnected and connected.  If the cat is clogged, the pitch will rise noticeably.

[nipper]

Or a simple vacuum gauge will tell you if the cat is clogged. 

[idosubaru]

After dodging the issue of the P0420 code for about 8 months, my son's car really starting to run terribly.

I wanted to find out if there are any aftermarket catalytic converters that someone would recommend.

I want to get another 2 years out of this car. I have heard from one mechanic that the aftermarket converters are junk. It would be hard to justify spending the money on the Subaru brand, since his car is probably worth that amount. The car is not running well at this point, so I have to make a decision this week.

 

you do not need a catalytic converter.  

the P0420 code can not cause running issues - it's impossible for the rear sensor to cause the engine to run poorly because the ECU doesn't even use the rear O2 sensor for running. 

so if you "fix" the P0420 code you'll still have running issues. 

disconnect the rear O2 sensor and see if that changes anything, just for kicks.

 

even if you want to "fix the P0420 code" due to the check engine light - i wouldn't bother worrying about it until you get the drivability issue under control.  a nice clear converter with no P0420 on a car that doesn't run well/isn't trustworthy is a pretty bad idea in my book. 

 

1. start a new thread with the running issues and all the check engine light codes. 

2. mileage and have plugs/wires ever been changed?

[nitroman58]

Mileage is 102,000. Plugs have not been changed since we owned it, which was 83,000 miles on it. Because my son is away at college, it is hard to deal with this from a 200 mile distance.

Plugs should be reasonable to change, and ask the mechanic to check the rear O2 sensor correct?

[DaveT]

I haven't seen an o2 sensor cause crummy drivability. I've seen them cause a trouble code, burn out a catalytic, poor fuel economy.

 

Unrelated, but at 100 miles you are due for timing belt and idlers.

[idosubaru]

Start here: 

*** Read the check engine codes and post them all on here, the actual 4 digit numbers. 

Any advance auto parts or autozone will do it for free, it takes 10 minutes or less.   

Or buy your own scanner on ebay for $20, they're super handy.   Plug it in and press enter and scan - it's really easy to use.

 

*** what is it doing when it's running bad? 

1.  starts fine or has trouble starting?
2.  idles fine or no?

3.  drives fine until it warms up, then it sucks?

4.  does it run worse when it's raining or humid?

5.  do the spark plug wires look ancient?

 

 

 

 and ask the mechanic to check the rear O2 sensor correct?

 

No!

changing the rear O2 sensor will not fix the drivability issues. 

it will still run just as bad as it currently is -so no, i don't recommend doing that. 

 

 

 

Plugs should be reasonable to change, and ask the mechanic to check the rear O2 sensor correct?

 

Probably not actually.  It might fix the problem, but it probably wont' too - so you don't really want to put money into a car that you don't want to keep. 

[nipper]

Wow so many places to start

 

This car needs a proper tuneup. Plugs Subaru wires fuel filter air filter. I et you have some bad plugs. PCV valve too.

 

Next your due for a timing belt, like it of not, with a water pump cam seals idler and tensioner. 

 

Then trace down the FRONT O2 sensor. Hell at this poin replace one then the other. Normally not my suggestion but the car hasnt been maintained all that well and thats coming home to roost.

[nitroman58]

Timing belt & water pump done!

[nipper]

Ok so I take back my unloved comment  

[brus brother]

Public Service Announcement: Buddy called me a few months back since his Ford E 250 van was barely able to make it up a hill and then not even able to drive on a flat road wanting me to follow him home. Never made it. Idled OK but wouldn't go at all under load. Long story short. Failing/misfiring coil packs over time killed the cat. Broke down the ceramic and so completely clogged it so that when I revved the engine in a parking lot, it actually blew some breather lines off the the valve cover. Disconnected the cat and vacuumed out the loose bits. Been running it as is for the time being and all is fine. Changed the coil packs and no more codes. Had been getting cat codes and misfire codes.

[idosubaru]

 it's worth a check - just disconnect the exhaust somewhere and drive the car.  if the issues go away - you just confirmed the converter is problematic. 

you can drop it from the engine (wear ear plugs it's super loud) and drive it around the block - if the issues go away you know it's the converter. 

or unbolt the flange in front of the catalytic converter and support the exhaust so it doesn't bang around.  if it drives fine - converter is the cause. 

 

that being said - other manufacturers have much higher catalytic converter failure rates, i think you can google "Make-model-so-and-so cherry red exhaust" and other descriptions of clogged exhaust and get significantly more hits than Subarus. 

[Bushwick]

FWIW, aftermarket cats aren't "junk". They typically have less precious metals than OEM have. Plenty of guys run aftermarket high-flow cats on turbo'd cars and have no issues. I have an aftermarket cat in other car and it's passed the last 2 e-checks w/o issues despite having a more performance oriented tune.

 

Some of the round high-flow cats can blow out the centers due to the way they rolled the substrate, but that seems to happen on high HP builds, and is easy to avoid by getting one that doesn't cheaply roll the substrate.