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I took my 2006 Subaru Legacy to local mechanic because the car would not accelerate above 65mph. He said it was a plugged catalytic converter. Deciding whether I should just replace the catalytic converter or delete the cat and get the car pro tuned. Pros or cons? Anything is helpful. I’m not real familiar with car tuning.
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Welcome. I am assuming you have a Legacy GT and not a 2.5i since you mentioned pro tuning.

 

If you don’t want to fall in the money pit of modifying your car and getting it tuned for almost each major modification, like removing a catalytic converters in your down pipe, I would suggest replacing the catalytic converter and be happy with how the car is now. A catalytic converter in your up pipe is not necessary and you should actually remove it to prevent damage to your turbo.

 

However, just keep in mind that the original tune on these cars are pretty garbage and it’s worth getting a Cobb AP for peace of mind and a little more power. But there’s few here that get the AP and stop there. If you choose to go this route there are plenty of threads loaded with information on here that you might want to read.

 

Also, the car wouldn’t accelerate over 65 mph because it was in “limp mode” which is a failsafe to prevent damage to the engine. This would mean it was throwing a check engine light code and knowing that code will help you make sure it is the catalytic converters that need to be replaced or you may have a different problem.

Edited by Notorious
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Thousands and thousands and thousands and thousands of Subaru turbo cars are out there running for hundreds of thousands of miles on the stock tune and never have an issue. It's the asshats like us that want to make a 2.5L turbo engine run 2000 AWHP that are the ones that blow up engines on a regular basis.

 

The stock tune, if driven as a daily driver and only driven with spirit once in a while, seems to work just fine, as many of the 200K+ cars will attest. It's not the best, but it also seems to not be the worst either.

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If people only knew half of the requirements OEM engineers have to work within they would marvel at how well things operate.

 

When Bill (Delicious Tuning) was working on the CARB tune for the Innovate S/C kit my eyes were opened to the legal restrictions put on the engineers by the state of California alone. Its ludicrous. The cars should self detonate every time they enter the freeway. But they dont.

 

Bills tune was finally accepted by the state. He is the first aftermarket tuner to ever have a tune CARB certified. He said the tune was "shit" and continued improving it outside the state regulations.

 

For what they are given and what they have to achieve, the stock tunes are very good at what they are for. If you want more power, it is available. But modding is generally a federal offense.

Edited by m sprank
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Back to the OP's question: what are your goals? If you just want the car to keep running, replace the cat and move on with your life. If you want the car to run a little better and a little faster, invest in a Cobb AccessPort and run the stage 1 tune. If you want the car to be substantially faster, then you start changing the hardware.

 

However, assuming you have a LGT, you have 3 cats. Which one(s) did he say was/were plugged?

Adding your car model to your profile is very helpful.

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Welcome. I am assuming you have a Legacy GT and not a 2.5i since you mentioned pro tuning.

 

If you don’t want to fall in the money pit of modifying your car and getting it tuned for almost each major modification, like removing a catalytic converters in your down pipe, I would suggest replacing the catalytic converter and be happy with how the car is now. A catalytic converter in your up pipe is not necessary and you should actually remove it to prevent damage to your turbo.

 

However, just keep in mind that the original tune on these cars are pretty garbage and it’s worth getting a Cobb AP for peace of mind and a little more power. But there’s few here that get the AP and stop there. If you choose to go this route there are plenty of threads loaded with information on here that you might want to read.

 

Also, the car wouldn’t accelerate over 65 mph because it was in “limp mode” which is a failsafe to prevent damage to the engine. This would mean it was throwing a check engine light code and knowing that code will help you make sure it is the catalytic converters that need to be replaced or you may have a different problem.

 

 

 

It was not throwing a CEL

 

 

Sent from my iPhone using Tapatalk

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If the catalytic converter is plugged, you have other, more serious problems with the engine. Catalytic converters are virtually good forever if no foreign material is introduced, but as soon as something else (oil, water, metal, etc.) is introduced, then the converter can become fouled and plug up.

 

I would look at the other things that can cause the converter to be plugged (unless it's broken, in which case, you will definitely need to replace it or remove it) as I have listed above. If you have excessive blow by in one or more cylinders, or perhaps an internal head gasket leak that could allow coolant or oil or both to enter the exhaust. Could possibly be valve seals, or even the PCV valve being completely plugged up, causing excessive oil burn.

 

There is something else going on there to plug up the converter. They don't just "plug up".

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Welcome. I am assuming you have a Legacy GT and not a 2.5i since you mentioned pro tuning.

 

If you don’t want to fall in the money pit of modifying your car and getting it tuned for almost each major modification, like removing a catalytic converters in your down pipe, I would suggest replacing the catalytic converter and be happy with how the car is now. A catalytic converter in your up pipe is not necessary and you should actually remove it to prevent damage to your turbo.

 

However, just keep in mind that the original tune on these cars are pretty garbage and it’s worth getting a Cobb AP for peace of mind and a little more power. But there’s few here that get the AP and stop there. If you choose to go this route there are plenty of threads loaded with information on here that you might want to read.

 

Also, the car wouldn’t accelerate over 65 mph because it was in “limp mode” which is a failsafe to prevent damage to the engine. This would mean it was throwing a check engine light code and knowing that code will help you make sure it is the catalytic converters that need to be replaced or you may have a different problem.

 

 

 

Can removing the catalytic converter cause other problems?

 

 

Sent from my iPhone using Tapatalk

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Can removing the catalytic converter cause other problems?

 

 

Sent from my iPhone using Tapatalk

 

Removing the first catalytic converter in the up pipe is fine, you may just need to do a bit of wiring so the car doesn't notice it is missing. You can replace it with a catless up-pipe or an STi up pipe if you can source it. Removing the catalytic converter in the down pipe too will result in overboosting and you won't be able to pass emissions testing. It's also illegal and pretty bad for the environment, but many do it without getting caught.

 

If the car did not throw any check engine lights, then it might not be the catalytic convertor that caused it. It usually throws a P0420 when there is something wrong with the catalytic convertor or your rear O2 sensor.

 

Look for any disconnected vacuum or boost lines, especially the blue T connector underneath the intercooler. Any modifications or maintenance on the car recently?

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Back to the OP's question: what are your goals? If you just want the car to keep running, replace the cat and move on with your life. If you want the car to run a little better and a little faster, invest in a Cobb AccessPort and run the stage 1 tune. If you want the car to be substantially faster, then you start changing the hardware.

 

However, assuming you have a LGT, you have 3 cats. Which one(s) did he say was/were plugged?

Adding your car model to your profile is very helpful.

 

 

 

Mechanic says the catalytic converter right before the turbo.

 

 

Sent from my iPhone using Tapatalk

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2.2K ohm resistor between the two wires for the EGT and it will be happy forever. Put in a catless up pipe and you should be good to go. Do it yourself. You need to learn a bit about these cars and to replace the up pipe, it's just nuts and bolts. There are a lot of threads on here on how to do it.

 

If that converter is plugged, then again, you need to look at potential other issues that caused it to be plugged. Oil and/or coolant could be the issue. PCV being plugged can cause it to use excessive oil and that will also be a situation where it could damage the turbo seals. You need to check the PCV immediately and make sure it's not all plugged up too.

Edited by JmP6889928
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Sell the car. Buy a honda.

 

LOL! Yeah, I hear that. Damn boost is addictive. If I bought a Honda I would be doing the same thing as I am to this LGT.

 

That being said, my mods are mostly handling and reliability. Yes, I tuned it but it felt necessary with a 5eat or I would have had to sell right away.

 

The next car will be a Lexus IS350 AWD.

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Well, that sucks. Sorry to hear that.

 

Mike is spot on about metal in the engine. Hopefully the turbo held together and didn’t break up and cause other issues. Make sure to check all banjo bolt screens to make sure they are not clogged. Many guys replace the turbo and skip this step. Then then the turbo starves for oil and dies quickly after replacing.

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Well, that sucks. Sorry to hear that.

 

Mike is spot on about metal in the engine. Hopefully the turbo held together and didn’t break up and cause other issues. Make sure to check all banjo bolt screens to make sure they are not clogged. Many guys replace the turbo and skip this step. Then then the turbo starves for oil and dies quickly after replacing.

Or there is contamination and the bearings check out shortly after the turbo replacement.

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