time needed to clear out cats after running rich

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RPMster

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Since I'll be going in for a smog check soon, I got to thinking...

My car had been running rich all summer due to a bad A/C pressure sensor. I had noticed heavier soot deposits on my chrome exhaust tips during that time. I pulled the codes and replaced the sensor about 5,000 miles ago. I'm assuming that 3 to 4 months of running rich could have mucked up my catalytic converters a bit.

Here's my question: Should the past 5,000 miles of clean running have been enough time to clear out any junk that built up in my cats? I'm assuming such deposits will tend to clear out over time. The car gets about 200 miles of steady freeway driving every week.
 
Best thing to do is take the car out for long highway speed drives which gets the substrate up to a temperature that will burn off the soot and carbon deposits, also another way is to disconnect the maf and let the car run in open loop mode which will heat the converter up a bit more than normal ...BUT only allow this for thirty minutes at a time or less. You will smell the converter heating up and burning off extra deposits when you do this.

FTR I have done the disconnected maf open loop burn off method and it works safely if done for a short period of time. No damage at all to the converter or substrate.
 
Last edited:
I have read on here before that using TC-w3 in your gas at a 500:1 ration, 5 gallons to 1 ounce, raises the cat's temperature more than normal, thus making a older and dirtier one more efficient because of the higher temp burning off deposits.
 
Originally Posted By: RPMster

Here's my question: Should the past 5,000 miles of clean running have been enough time to clear out any junk that built up in my cats? I'm assuming such deposits will tend to clear out over time. The car gets about 200 miles of steady freeway driving every week.


5k and a lot of highway should be enough time for the cat to get hot and do its thing. If your going to a smog test soon and wondering about cat contamination dont use anything that will add load to the catalyst (fuel injector cleaners, etc.)
 
Originally Posted By: Brenden
I have read on here before that using TC-w3 in your gas at a 500:1 ration, 5 gallons to 1 ounce, raises the cat's temperature more than normal, thus making a older and dirtier one more efficient because of the higher temp burning off deposits.


I think thats what Scotty Kilmer's gallon of lacquer thinner trick does. Too scared to do it. I replaced the cat.
 
Does Cali still do a 'sniff' test or simply check for OBDii codes ?? Emissions here only check for codes but when they used to do the sniff test, one of the best solutions was run the tank down to about 2 gallons and add about 3 bottles of HEAT.
 
Give it an Italian tune up. A good 20 minute run up the highway in either 2nd or 3rd. Just keep up with traffic, but at higher RPM. That will clean it out .
 
I'm assuming the bad sensor set off your CEL? If it did, there's a chance the cat is already fubar.

I would just take the car in and have the emissions test done. Base your next move on the test results.
 
Originally Posted By: paulo57509
I'm assuming the bad sensor set off your CEL? If it did, there's a chance the cat is already fubar.

I would just take the car in and have the emissions test done. Base your next move on the test results.


What I'm thinking as well.
 
Originally Posted By: partspro
Does Cali still do a 'sniff' test or simply check for OBDii codes ?? Emissions here only check for codes but when they used to do the sniff test, one of the best solutions was run the tank down to about 2 gallons and add about 3 bottles of HEAT.


CA does both sniff test and OBDII check. I use Chevron 91 octane (Premium here), which I'm thinking should run plenty hot by itself.

Originally Posted By: andyd
Give it an Italian tune up. A good 20 minute run up the highway in either 2nd or 3rd. Just keep up with traffic, but at higher RPM. That will clean it out .


Yep, I'm planning a good 20 to 30 minute freeway run right before the test.

Originally Posted By: paulo57509
I'm assuming the bad sensor set off your CEL? If it did, there's a chance the cat is already fubar.

I would just take the car in and have the emissions test done. Base your next move on the test results.


Nope, CEL was never illuminated. The things that tipped me off were the rough idle and lack of power. I first tried cleaning the throttle body. No luck. Then tried two tanks of gas with a bottle of Techron added to each tank. No luck there either. At this point I figured that I had some codes that were stored without activating the CEL. Sure enough, I found the high/low DTC codes for the bad sensor. Changed the sensor. Done.
 
You can try a highway drive for 20 minutes at elevated speeds.
But a cat that has been exposed to prolonged richness may never be the same.
This is a cat killer.
 
Why would a bad ac pressure switch have anything to do with running rich? Either the ac wouldn't work, or it would run when it shouldn't.

It really doesn't have anything to do with anything other than the ac.
 
@Antonmnster: As far as I know, the sensor is involved in telling the ECM to idle-up the engine or idle-down the engine based on compressor operation. Not to be confused with switch that shuts the compressor on and off. The sensor had gone haywire, and it was constantly sending mixed signals to the ECM, somehow causing the engine to run rich as a result.

I had the day off from work today, and decided to get the smog check out of the way. Here are the results (passed with wide margins):

smog2011.jpg
 
Originally Posted By: RPMster
@Antonmnster: As far as I know, the sensor is involved in telling the ECM to idle-up the engine or idle-down the engine based on compressor operation. Not to be confused with switch that shuts the compressor on and off. The sensor had gone haywire, and it was constantly sending mixed signals to the ECM, somehow causing the engine to run rich as a result.

Good info. Battling a rough idle when the a/c is on for a while now. There is an idle up when the fans kick in, not the a/c. Assumed the compressor was on its way out, this gives me something else to look at. Thanks!
 
Originally Posted By: LeakySeals
Originally Posted By: RPMster
@Antonmnster: As far as I know, the sensor is involved in telling the ECM to idle-up the engine or idle-down the engine based on compressor operation. Not to be confused with switch that shuts the compressor on and off. The sensor had gone haywire, and it was constantly sending mixed signals to the ECM, somehow causing the engine to run rich as a result.

Good info. Battling a rough idle when the a/c is on for a while now. There is an idle up when the fans kick in, not the a/c. Assumed the compressor was on its way out, this gives me something else to look at. Thanks!


Compressor is probably fine unless low refrigerant . The older toyota's had an idle up(vacuum) switch for the a/c's and I know that toyota does not change their technology very often. The newer ones have an iac. It is on the throttle body on the newer cars and you have to remove the throttle body to clean it.
 
Normally, the engine will idle up to stay the same with the AC on.
but this is not from the AC sensor, it is from the crank sensor, which tells RPM.
ANY load, not just AC, will do this.
But the actual RPM should not be higher than normal.
 
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