Front or rear Cat Converter?

[suby85]

I need to replace my cat so I can pass DEQ and get new tags. The problem is what section is the cat. The front were the two pipes meet is considered the front converter and the second section is considered the rear converter. Which one is the actual cat converter?

[WoodsWagon]

Well, knowing the year and engine setup in your car would help. Carb/fuel injected for one.

 

Usually the front cat is the the one that does most of the work.

Why do you think it needs a cat?

What were the readings that failed you?

[suby85]

OOP's, sorry. I guess no one can read minds. 1994 SPFI Loyale with 92 engene and ECU also SPFI. 1st idle HC - 411 and CO - 2.6246, 2nd idle HC - 396 and CO - 3.0051. HC should be 220 or less and CO should be 1. The reason for thinkign I need a new cat was taking it to a shop that the I tow cars into all the time and we get free labor and parts at wholesale. I had them check it out and they said everything checks out fine so it has to be the cat. I was told by the guy at DEQ that it was running to rich, so I put an Accell Superstock coil in and replaced the Bosch Platnum plugs with one step hoter NGK's. These readings were after doing these changes. The only thing I could think of that would stillmake it run rich was a bad O2 sensor, but the guys at the shop said it was still good. I am stumped as to what Ishould do, that is why I am posting.

[WoodsWagon]

On that car the front cat is the only cat, the second thing that looks like a cat is really nothing more than a resonator. However the cat is part of the y-pipe manifold so it's harder to replace.

 

High idle HC's and CO means your running rich. There's really not enough heat coming out of the engine at idle to keep the cat lit off, so a cat won't have much effect on idle readings.

 

Leaky injector, restricted intake, dirty MAF sensor, or most likely a bad coolant temp sensor or corroded wire leading to the sensor could cause that. If the ECU doesn't think the engine has come up to operating temp, it will run rich, much like the choke staying on a carb until the engine's warmed up.

[suby85]

when I took it through DEQ, I disconected the electric fan and I don't have a clutch fan. The engene temp got up to nearly the red from having to sit for so long. I figured the temp sensor had to be working to get that reading, and the cat had to have gotten pretty warm.

[idosubaru]

On all the EA/ER vehicles i'm accustomed too the front y-pipe cat is a pre-converter and the one after that is the actual converter?

 

that being said i would never replace the converter on this car. try to keep it as long as you can. cheap aftermarket converters rust out in a year. i'd try to keep the original if there's any chance.

 

if the ignition components are in question at all - replace the plugs, wires, cap, and rotor. when i lived in maryland i passed emissions numerous times by a simple tune up.

 

if that didn't work i'd do those tricks - get whatever kind of gas is best for passing and add those bottles of "pass emissions in a can" stuff.

 

if you're still amped up to replace it then make sure they're welding in something that will actually last. nothing more annoying than your $100 worth of work rusting out in a year or two.

[suby85]

Trust me, I don't want to replace the cat if I don't have to. All I want is for the car to pass DEQ.

 

So far the things I have done are, replace the injector with the one out of my 94 engene (I don't know if it factory or not due to the PO replaced it be fore I bought the car), removed the clutch fan and rewired the electric fan, replaced the coil with an accel superstock, put in NGK plugs the are one step hoter than OEM's, and replaced the muffler with a turbo muffler.

 

The engene still ping and knoks slitly when going up steep hills, but not real bad. I always thought that was from running to rich, but was not sure what was causing it.

 

Is there anyway to check the O2 sensor? I have talked to two other friends that are mechanics and they both say it sounds mor like the O2 sensor. They said it wouldn't matter how hot or cold the engene was, if it was going bad it would make it run rich.

[Gloyale]

That Superstock coil is not helping anything.

 

Likely you will fry the ignition module if you leave it in there.

 

Take it out, spark isn't the problem. If the old coil worked you are much better off with it.

 

replace the Cat and you will be fine.

[987687]

when I took it through DEQ, I disconected the electric fan and I don't have a clutch fan. The engene temp got up to nearly the red from having to sit for so long. I figured the temp sensor had to be working to get that reading, and the cat had to have gotten pretty warm.

 

Could still be the CTS. There's 3 censors for temp in your car. One for the electric fan, one for the gauge, and a different one for the computer. Just because the gauge works doesn't mean the one to the computer is working.

[suby85]

Finally gat to talk to my local independant Subaru machanic who has been working wonders with Subaru's for years. He confermed that it is the cat and it is the front cat due to it doing most of the work.

 

As far as the superstock coil doing nothing, I beg to differ with you. After replacing the coil, there was a significant differance in performance and stoped the pinging and knocking. Also as far as burning out the ignition module, I also asked about that, and he informed me that it was fine and would do no damage. The only thing it might do is make me replace my cap and rotor more often.

[WoodsWagon]

Have him hook up his select monitor scan tool to the ECU and make sure the temp reading matches the actual temp of the engine. If the CTS reads low, or there's corrosion in the wire making it read low, then the ECU will never go into closed loop operation. Closed loop is where the ECU adjusts the fueling based on 02 sensor readings.

 

So, if the CTS or the wire connecting the CTS to the ECU is bad, the ECU won't even bother looking at the O2 sensor. As said earlier, there's 2 temp sensors and 1 temp switch for the fan on the engine. Make sure you're dealing with the right one.

 

O2 sensor mabe, but it's unlikely that it's used at idle. Same thing with the Cat, it's not really used at idle.

 

Idle fueling is controled by the coolant temp reading and the MAF reading. It's an open loop base map pretty much, ECU adjusts fueling based on MAF (air coming in), CTS (engine up to operating temp or not) and controling the RPM's with the IAC(idle air bypass).

 

So, it's probably not the cat, or the 02, so try cleaning the MAF sensor with MAF sensor cleaner, and check/replace the ECU's CTS (not the gauge one!) and wire, which is known to get corroded.

 

Or go ahead and thow a cat at it, hope that it converts enough HC's and CO's to CO2 and hope you'll pass. Then do the same thing when it fails next year.