Several months ago, a friend of mine bought a mostly stock ‘03 WRX. All was well until a few weeks ago, when he got a check engine light and was noticing a lack of power. Using the ever-useful “beater” laptop with FreeSSM, I was able to pull an Exhaust Gas Temperature Malfunction code (P1312). Us two, and another good friend, were able to correct the check engine light with a 2.2kohm resistor. However, the lack of power still remained. A test-drive while using real-time monitoring with FreeSSM and watching the installed boost gauge showed that no boost was being produced, and the wastegate solenoid was behaving as expected. There were no cracked hoses or exhaust leaks. With these things in mind, there were a few possibilities for the cause of the issue. However, I had a gut feeling what the problem was...

In the US market, the 2002-2005 WRX, 2004-2005 Forester XT, 2004-2006 Baja Turbo, and 2005-2006 Legacy GT and Outback XT had a pre-catalytic converter in the joint-pipe (commonly known as the uppipe). The joint-pipe is the pipe that connects the header to the exhaust inlet of the turbocharger. Also included is an Exhaust Gas Temperature (EGT) sensor, intended to monitor the temperature (and in theory, the health) of the pre-catalytic converter. In some cases, the pre-catalytic converter can break apart and get sucked into the turbocharger (also taking out the EGT sensor in the process).

As you can probably imagine, that’s not a good thing...

The WRX owning friend came prepared with a new TD04, expecting to replace a seized turbo last Friday evening. Myself and the two other people who were now helping him on the job were hoping it was just going to be a simple turbo swap. Wishful thinking on our part... the turbocharger was completely seized, with chunks of pre-catalytic converter falling out of the turbine wheel housing... we knew we had some work ahead of us...

Advertisement

It was at this point that we know both the joint-pipe and center-pipe (dump pipe) needed to come out. As the dump pipe was pretty much permanently attached to the rest of the rear section of the exhaust due to 14 years of PA winters, we were pretty much forced to remove the entire rear section of the exhaust in one piece. That was fun without a lift... The picture above shows what came out of the dump pipe.

Removing the joint-pipe involved fighting rusted bolts with penetrating oil, a blow-torch, and eventually, a grinder. When we finally got the joint-pipe off, we saw that what remained of the pre-catalytic converter was loose inside the pipe. Even before we discovered that, we knew the pre-catalytic converter needed to be removed from the system to prevent damaging the new turbo. Going for the cheap option, we decided to gut the original joint-pipe. This was the result:

Advertisement

Gutting the joint-pipe was a lot more difficult than we anticipated. What remained of the pre-catalytic converter was quite robust, requiring the use of a hammer and chisel, and eventually, a hole-saw.

Reassembly went better than disassembly, however, it still wasn’t completely smooth. After fighting with the joint-pipe for what seemed like forever, we finally got the exhaust reinstalled. By comparison, installing the new turbo was fairly easy.

By the time we had everything put back together, the turbo primed, and the coolant level topped off, it was past 3am on the second evening we worked on the project. We all went for a test drive, and other than all of the smoke and steam from all of the penetrating oil used and coolant spilled, it ran perfectly.

Advertisement

In the end, the project was a great success, and us inexperienced mechanics got some valuable wrenching experience. However, I have a newfound hatred for pre-catalytic converters...