Well, I've put a gallon of lacquer thinner in a 1/2 tank and I'm running through it now. I'll let you know if the cat codes come back.
In the meantime, my evap test has finally finished, and I'm getting the P0455 - Large Leak detected. As if I don't already have enough problems w/ this car. Anyway, I have previously replaced the gas cap, as well as the gas filler pipe. I guess I'll try to take care of this problem first.
-Paul

 

I think both of these guys are great - I've watched several of their videos and they both are very knowledgeable.
I do not think that Eric is saying that it definitely doesn't work - he's saying that it didn't work in this case, and that cats can fail for a large variety of reasons - not all of which would be solved by simple cleaning. Not to mention that he only used one quart of thinner in a 3/4 tank of gas - which is far less then the recommended one gallon in half a tank. But even if he did use the full gallon, the cat in that car may have been too far gone to help anyway, or have been broken for an entirely different reason.
I would be inclined to lean more towards Scotty's conclusion, based on years and years of actually using this method.
BUT we'll see how my car does!
-Paul

 

Couldn't have said it better myself. It's worth trying! Especially for the cost vs benefit!

 

Update on current status: I brought the car to the shop to check on the P0455 - large leak. And they stated that they could find NO LEAK. They checked multiple times, smoking the system, etc. Their theory is that some valve is occasionally sticking open, causing the error. Do you guys have any ideas on that?

As for the cat codes. The CEL has been reset, and now we'll see if the CAT codes come back after my little experiment with the lacquer thinner.
-Paul

 

EVAP Large Leak Detected: The P0455 code does not mean a large leak is detected.
– The ECM has detected a large leak in the EVAP system during a system monitor test

Probable Causes

1. Defective, loose or missing fuel cap
2. EVAP canister broke, hose cracked or not connected
3. Purge or vent solenoid defective
4. Vacuum leak at engine

Check gas cap for dirt, crud around the seal. You want to make sure the gasket is in good condition and the filler neck where it meets the cap is not too rusty. If there is any doubt, replace the cap.

 

Hi,
The gas cap is brand new OEM, and the filler pipe is brand new. All the vacuum hoses have been replaced and rechecked too. The ABV valves are also new. A cracked or disconnected hose would have showed up in the smoke test. That leaves a defective purge or vent solenoid, which may be sticking intermittently, which would explain why the shop found no leaks.

 

check that the filler pipe is properly tight. check that the evap hoses and the purge solenoid hoses are connected to their correct position. do you smell gas? if you do, there is an air leak in the sistem. p0455 should not give you problems on the way the car drives or run. but the smoke means the engine is burning oil and that could affect the catalytic converter and the way the car runs. for example, it could create a false rich condition and the computer will try to lean out the fuel mixture. if you have a scanner, give us the short term fuel trim and long term fuel trim (stft, ltft). give us all the info you can. i bet the ltft would be at around -25% and the short term fuel trim at about -15% or so...

 

Update on the lacquer thinner experiment: The P0421 (bank 1) has come right back, but the P0431 (bank 2) has not. It has been about 12 days since CEL reset. Partial success? Maybe. But more time will tell. One thing for sure, the mode 06 test for the bank 2 HO2S switching time ratio is also passing with flying colors. I believe that is the precat test. I'm hoping that I've at least cleaned up one precat enough not to have to replace it.

-Paul

 

Hi, Juanky,
Yes, I do smell gas on occasion - not always but maybe every 3rd day or so. Sometimes the smell is very strong. I got the fuel trim numbers from Torque:

LTFT Bank 1: -3.9%
STFT Bank 1: -3.1% to +3.1%
LTFT Bank 2: -6.2%
STFT Bank 2: -3.1% to +2.3%

These numbers appear to be fine. Long-term the negative number means a slightly lean condition? But I think those numbers are within normal range.
Let me know what you think - and if there are any other tests I can run that will give us useful info - Torque has all sorts of data & can grab.
What could a P0455 mean when fuel trim is ok? Could my mechanic be correct and that something is occasionally sticking open to cause the conditon, but most of the time there is no leak?
I will check those other items you suggested too.
Thanks,

-Paul

 

0455 is gross leak. 0422 is small leak. i would first suspect the vacuum system, but if it has been smoked, it would have shown. purge control solenoid is on the same bracket as egr vent/vacuum, below the abv vent/vacuum. these solenoids get a lot of heat from the rear precat. i know for sure that abv vent/vacuum solenoids are greatly affected by heat. in the early stages of failing, the car will run fine until it has run for some time. then it will start going limp home, and ce will throw 1525/26/40 dtc. if you ohm the solenoids when they are hot, and failing, they will ohm high, or 0, which means they are bad. when they cool down, they ohm within spec, and they operate withing spec. if your purge solenoid is also doing this, that would explain the intermittent dtc. in my experiences with these cars, a lot of problems are cause by the vacuum system. and, looking at the vacuum schematic, a malfunctioning purge solenoid CAN affect running, but i think it would also throw another code. also, heat changes the sizes of vacuum line that is old and hard. so, if when the car has been running a long time, and the vacuum system is hot, you can get leaks, and you can get solenoids malfunctioning. i think there are like 13 solenoids in the 2.3 vacuum system. fsm also points to the map sensor, which is partially controlled by-a what? solenoid. this solenoid is also part of the vacuum system. fsm has function tests for each solenoid, but remember, i know abv vacuum and vent test good when cool, and bad when hot. i have never had problems with the other solenoids, but that dont mean they dont go bad