Hi, had a misfire the other day. P0302. Also got the code PO446 earlier that morning which looks like EVAP malfunction.

2002 LS430 with 113k miles.

I was stopped at a red light in traffic and the engine started idling hard, I could feel a thump/rumble repeatedly. Engine light blinked a few times and disappeared. I pulled over and checked the codes and it showed P0302 misfire on cylinder 2. I shut off the engine, turned it back on and drove home. No issues since, and I've driven it to and from work once since this incident without issue.

What am I looking at to replace in the EVAP system and am I correct to assume it caused the misfire?
Any advice appreciated

 

I don't think that there is enough evidence to just go changing parts as the problem disappeared on its own (yay). Unless of course you feel like guessing.

The missfire could be any number of things, including the vvt solenoid playing up causing an erroneous code and or computer guessing that is the evaporative system.

If you have a techstream cable then you could run some diagnostic tests on the evaporative system, the vvt system and a couple of other things.

Otherwise I would drive it some more and if/when the problem comes back then get started diagnosing things.

 

Thanks. I've been driving it a few days and so far it has seemed fine up until just now, I was in traffic again and it begun idling really hard. Like you can feel the engine thumping (for lack of a better description). But this time the engine light did not go on. I scanned the codes to double check and there was no codes at all. It happened for about 30 seconds then stopped and was fine on the ride home. I guess I'll bring it into a shop to figure out what's causing the rough idling, that seems to be the issue. gotta pinpoint it

 

There are generally no codes unless the check engine light is on. It's also really hard to diagnose when there isn't a problem present.

Depending on the data scanning setup you have you could just drive with the app running, datalogging all trips until it happens again. Then you will at least have some sensor data to look into - say MAF, TPS, O2S1, Cam angle, timing and rpm.

The symptoms sound quite a bit like one or both of the vvt solenoids beginning to play up. I stress this is a completely circumstantial feeling based on how mine was behaving when I first bought it with intermittent rough idle that turned out to be vvt solenoid issues.

Symptoms I had at the start was an intermittent rough idle often with no codes. Sometime turning it off and on would run perfectly again. Sometime just by revving up (in neutral) and letting it drop back to idle - kindle like it fixes it some of the times but not everytime. Some of the codes I got in the beginning were different cylinder misfires and some random codes. Cleared the code and would get different codes the next time it happened. Eventually after a week or two the computer decided to show vvt codes which new solenoids did fix the problem......

The vvt system runs off engine oil pressure which assumes flow so a couple of further diagnostic questions:

Have you checked the oil level recently?
When was the last time you (or someone) changed the oil? If it has been a while might be best just to renew the oil with the correct grade for your climate and see what happens
What's your cars service history like?
Has the PCV valve ever been refreshed? If it hasn't been renewed, it probably should be sooner rather than later, along with the seal which will likely be rock hard and brittle.
What condition are your vacuum hoses in? 3UZ's at this age are very prone to having their hoses go hard and brittle from years of engine heat which in turn creates intermittent issues with air leaks. If they are original it is a good idea to replace them all in one go as a set. It's not a big job as there is only about 10 of them mostly at the top of the engine.

See how you go

 

This is extremely useful information, thank you!!! I'm going to do some researching on all of this and see what I can come up with before I take it anywhere. Thanks again, and I'll post with a followup as I figure out more.

 

One important thing I forgot to mention: The car is not going above 3,000 RPM at all. That seems to be the limit, even with PWR selected.

Okay, so far:
I've replaced the air filter, it was filthy.
Oil was changed 3500 miles ago, it's due soon.
As far as I'm aware PCV valve has not been replaced. Neither the vvt solenoids. These both seem like simple repairs so I will get around to doing those ASAP.
Vacuum hoses are not in great condition. I immediately noticed two that need to be replaced immediately.

The first is on the passenger side of the engine. You can see about the middle of the photo is a cable taped up with electrical tape. This piece was cracked and open. I temporarily taped it until I find the proper hose to replace it with.


The second is the hose above my finger. It is supposed to be connected to this box. (EDIT: I ordered this part. it's part 23818 for anyone curious. Still searching for the other hose part number)


second angle


After electrical taping both of these cables back together (temporary until I find the proper parts) I noticed in neutral the car does rev up past 3000RPMs

 

Sounds like great progress. Those hoses have certainly reached replacement age.

In my car that little box, where the connector snapped off in the hose - it was deleted before I bought mine. It runs fine without it. I'm not even sure what is is there to do but they have a reputation for snapping just like that. We removed it in my friends LS when his snapped there and it is running fine without it too.

You may not even need to replace the vvt valves yet given the cracking vacuum lines, but as you say they are simple to replace if you want to do them anyway for peace of mind.