Thought I'd share this for some of you who are also nerds about this sort of thing.
Background - 2003 LX470. 275,000 miles
A year ago, I did the valve cover gaskets. About a month after, I started getting P0420 code. A few months after, the P0430 code came in as well. Catalyst below efficiency.
I wasn't able to find anything obvious that would cause this, not that I looked very hard, so I just kept driving with it. I did notice that in the summertime, when I'd go on lengthy highway drives, the code would clear itself. But when I resumed my normal daily city driving, it came back. Hint #1?
Another thing I noticed in the last month or two is that the oil filler neck, where it gets bolted on to the engine, was seeping oil. I took the two nuts off and cleaned up the mating surfaces and gasket, but it still seems to be leaking a bit. Hint #2?
Yesterday, I decided to look at the PCV valve. The valve appeared to be fine, and I could hear it rattle when I shook it around. However, the hose was brittle and cracked. Hint #3?
I'm thinking that the hose was disconnected when the valve covers were being replaced and that cracked the hose. Therefore, there was a vacuum leak between the throttle body and the PCV valve. The engine was getting unmetered air that wasn't going through the MAF, and it was throwing off the fuel trims, messing up the readings from the O2 sensors and ultimately confusing the computer into thinking that the catalysts aren't doing their job. Also, because of the absense of a vacuum, there was no vacuum to pull the PCV valve open to relieve pressure, so the built up pressure in the crank case found its next weakest point, the brittle gasket of the oil filler neck.
After replacing the brittle PCV valve hose and clamps, the next morning, I started the car and it immediately stalled. Twice. On the third try, it started up and ran OK. Drove 5 minutes to a parking lot and turned it off. Started it up again and it stalled. Re-started and it runs fine now. Hint #4?
I'm thinking the computer was used to excessive air coming in through the leak and is used to running way more fuel through the engine to compensate for it. Now, all of a sudden it's getting way less O2 than usual, so it starts out giving it the usual amount of fuel, and because of the excessively rich mixture, it stalls until the computer tries to reduce the fuel.
Do my analyses make sense or are there other factors I'm missing?
Curious about your thoughts.
Background - 2003 LX470. 275,000 miles
A year ago, I did the valve cover gaskets. About a month after, I started getting P0420 code. A few months after, the P0430 code came in as well. Catalyst below efficiency.
I wasn't able to find anything obvious that would cause this, not that I looked very hard, so I just kept driving with it. I did notice that in the summertime, when I'd go on lengthy highway drives, the code would clear itself. But when I resumed my normal daily city driving, it came back. Hint #1?
Another thing I noticed in the last month or two is that the oil filler neck, where it gets bolted on to the engine, was seeping oil. I took the two nuts off and cleaned up the mating surfaces and gasket, but it still seems to be leaking a bit. Hint #2?
Yesterday, I decided to look at the PCV valve. The valve appeared to be fine, and I could hear it rattle when I shook it around. However, the hose was brittle and cracked. Hint #3?
I'm thinking that the hose was disconnected when the valve covers were being replaced and that cracked the hose. Therefore, there was a vacuum leak between the throttle body and the PCV valve. The engine was getting unmetered air that wasn't going through the MAF, and it was throwing off the fuel trims, messing up the readings from the O2 sensors and ultimately confusing the computer into thinking that the catalysts aren't doing their job. Also, because of the absense of a vacuum, there was no vacuum to pull the PCV valve open to relieve pressure, so the built up pressure in the crank case found its next weakest point, the brittle gasket of the oil filler neck.
After replacing the brittle PCV valve hose and clamps, the next morning, I started the car and it immediately stalled. Twice. On the third try, it started up and ran OK. Drove 5 minutes to a parking lot and turned it off. Started it up again and it stalled. Re-started and it runs fine now. Hint #4?
I'm thinking the computer was used to excessive air coming in through the leak and is used to running way more fuel through the engine to compensate for it. Now, all of a sudden it's getting way less O2 than usual, so it starts out giving it the usual amount of fuel, and because of the excessively rich mixture, it stalls until the computer tries to reduce the fuel.
Do my analyses make sense or are there other factors I'm missing?
Curious about your thoughts.
