HCAC replacement

I would first replace both 02 sensors and see what happens. How many miles are on the car? I really doubt that it is a bad convertor. Sorry I have no experience with trying to use an aftermarket exhaust..Let us know what happens.. By the way,WELCOME TO THE FORUM!!!

 

I am pretty sure the HCAC is not in that loop.

Let me suggest:

• photos of the part and area - some have reported using high temperature lubricants and working the valve loose (WD-40, e.t.c.) careful on first start to have an extinguisher handy and able to work the area.
• Technical Information Service - download the sections dealing with HCAC and/or get the maintenance manuals (Ebay).

Bob Wilson

 

High, I own a 2002 prius with a reinvolt battery and 207000 miles. My HCAC was squeaking and operated slowly until I lubed it. Unless it is corroded, your HCAC may only need to be lubricated. Use a very high temp lube like dry slide or anti seize. The valve is vacuum actuated and spring loaded in the opposite direction. Just connect any hand operated vacuum pump to the actuator and you can operate the valve to test it. Also make sure that you have no leaks at each end of the vacuum line that connects to the actuator. Concerning p0420, cat below efficiency: I could not drive 65 mph without setting code p0420. Code p0420 means the cat is dirty, not operating at full efficiency, but hopefully, not damaged. I could not afford to throw money away on a new cat or on o2 sensors unless it was absolutely necessary. So after some research, I decided should try cleaning my cat. I read that fuel additives that claim to clean the cat can overheat the cat and destroy it so I did not try them. I did find 2 safe cleaning methods online: News - BioEd Online using citric acid to clean the cat , and all over youtube, soaking the cat in soapy water. I cleaned my cat over thanksgiving weekend, 2012. I removed the exhaust system, only 4 bolts and 1 support. The hardest part was unplugging the rear o2 sensor located under the right front floor carpet. I removed the o2 sensor from the exhaust pipe. I inspected the cat. If it has chunks missing, it is done for. Mine looked good. I tried hot soapy water first. I used an electric griddle to heat my bucket full of soapy water and stuck the exhaust, cat end first into the bucket so that the cat was completely submerged. It stayed there, just below boiling temperature for 12 hours. I had to add more water several times and I agitated the exhaust up and down several times. I rinsed out the soap, reassembled everything, test drove, Failure! p0420 came right back. So, I tried again using the second method, but, I used 13 gallons of white vinegar in place of citric acid. They are very similar and white vinegar is easier to get than citric acid and vinegar is cheap. Same routine, soaked the cat in hot smelly vinegar for 8 hours. I stopped at 8 hours only because the white vinegar steamed off so fast that I ran short of vinegar after 8 hours. I removed the cat from the bucket. The cat looked great, no rinsing needed. But, the bucket and griddle looked pretty bad from exposure to the hot vinegar. Put the car back together, test ran, and no more p0420 code since thanksgiving 2012. The hot white vinegar worked for me. The hot soapy water may have loosened things up for the vinegar. I don't know for sure. But it was a good cheap fix for my p0420 issue.

 

What about the O{2} sensors? Did you change or clean them too?

Bob Wilson

 

Nope, my scangauge indicated that both o2 sensors were operating correctly, and the graphs showed that the cat was not operating correctly. When I removed the rear o2 sensor prior to cleaning the cat, the o2 sensor was clean, so I just reinstalled it later.

 

I understand your decision to do nothing.

If you later decide to do something, DTC P0420 points to the catalytic converter, not the HCAC. My first suggestion would be to replace the oxygen sensor upstream from the catalytic converter. A new, more responsive O2 sensor may allow the engine ECU to decide the catalytic converter is OK.

A second step, given your Maine location, would be to find a muffler shop that can cut the existing catalytic converter out and weld an aftermarket unit in.

 

Also, someone posted about using white vinegar, heated, to clean the catalytic converter. It would be a cheap fix if you can confirm it works.

Bob Wilson

 

The only impact of removing the HCAC is that your car will emit a bit more emissions during warmup, and your check engine light will be continuously on.

 

I no longer own my 2001 or its repair manuals, but I believe that the HCAC has a sensor which detects whether the valve is open or closed. If the HCAC is gone then the sensor will no longer be connected to the engine ECU. The ECU will log a DTC and turn the check engine light on.

 

I’m currently working on a replacement

 

Gen 1s are getting old enough that there have also been some recent "thereifixedit"-style posts about just routing the vacuum actuator hose to a dummy actuator so the ECM thinks it is moving something, and doesn't set a trouble code.