2005 LS430 Running Rich and Rough.

[Mile_High_Flyer]

She suddenly started idling very slow, and surging, When I got out and went around the back, the exhausts were emitting black smoke. When I got home, I left it overnight, and it seemed to be okay this morning, except possibly idling slightly high. This afternoon she was okay for a while, then started back with the surging and slow idle, At the lowest point, about 200 RPM the CHECK ENG message flashed on for a split secvond .  Other than that, there are no warnings, and one of my OBDII sensors showed no codes. Haven't checked my other sensor yet, I'll do that tomorrow.  At one stage I gave it heaps, and it appeared to be quite good for a while. When I got home, there was no smoke, but there was quite a smell. I've only just now thought , I wonder if the cats might smell through working hard because of how rich it was riunning . Could that be the case?
Any thoughts, anyone?
Thank you.

[Engel]

Similar thing happened a week ago.

2003/2004 LS430.

We were cruising in slow traffic, foot almost off the pedal, for about 1/2 hour driving up the length of the Gold Coast. 

After about 25 minutes like that, it started to misfire when we were at traffic lights.

If I kept slight pressure on the pedal to bring idle up to about 900-1000, then it smoothed out.

Gave it a normal run the next morning and the problem disappeared. Don't know if it was the constant slow running and maybe getting warm, or dirty fuel or something else.

Sorry that doesn't answer your question exactly, but at least it seems to have fixed itself after a good long run.

[2bling]

Check for air leaks, all rubber hoses on the inlet manifold and make sure every thing is plugged in MAF etc, definably running rich let us know how you go cheers.

[Mile_High_Flyer]

Seems to be all good again now. It was running fine, but even so, I did still pull MAF and clean it again, although it looked clean, and was done only a few months ago.  Also cleaned and vacuumed air filter, which again was done at the same time as the MAF, also looked clean. I'm obviously keeping a very close watch on everything at the moment!  It just seems strange that no Check Eng and no codes showed up.   

If anything else happens, I will let you know. I think it must have been one of those temporary glitches that computers can sometimes have, but I will check hoses etc.  One of my LS400s had a funny one too, some time ago. It sounded exactly like a hydraulic lifter not pumping up, but they don't have 'em!  Only lasted a very short while, and never did get to the bottom of it.

Thanks guys.

[Mile_High_Flyer]

Update. She appears to be running fine, and according to the fuel consumption figures etc, all is good, but she has to be still running a bit rich as the exhaust pipes are black, and there is still some smell, but I still don't have any codes from either of my OBDII checkers.  I am going to try disconnecting the battery for a while in the hope that it might reset the computer, but I'm not gonna hold my breath!!  Other than that, I don't know. Might have to bite the bullet and go and see Toyota.

[Mile_High_Flyer]

 Another update. I disconnected the battery for about an hour and a half to make sure there was absolutely no residual voltage, or anything else! Then reconnected and went for a 40km ride. (About 25 miles). Fuel consumption figures looked good, and when I got home, no smell, and exhaust pipes were a lot cleaner. So I cleaned them, then went for a 20km ride. Pipes as clean as a whistle. That was yesterday. Today I went to work this morning, and back this evening,  About 40 km each way 6.4L/100km, 36.75 mpg US. 44.14 mpg Imperial. Mainly on motorways (Freeways)  mainly about 80km/h, 50mph. and again pipes absolutely clean. I'm very happy with that. I have no idea what caused the problem, because the same tank of fuel was used all the time.    Cheers.