LS430inDE.

So this weekend we're in Nashville to attend a wedding. We drove 2 vehicles, one being the LS.

Some of you may have been aware that I have had a CEL and VSC and TRAC idiot lights illuminated because of an exhaust leak. Surprisingly, at some point during the 12 hour/800 mile drive those lights cleared, and the lights are now NOT ON. They extinguished some time before the 1st fill up at a Shell gas station. We averaged about 26/mpg (better than her V6 Accord), and cruised with 'an average' speed of about 67mph. The speed limit most of the ride was 70mph, and I had the cruise control set around 76mph. It was absolutely SMOOTH and FAULT FREE SAILING-----until my first fuel fill-up.

At out first fuel stop, as I was pumping shell super-unleaded, I felt and heard a misfiring. Not thinking it was the LS, but curious to confirm, I quickly went to the back tail pipes and saw the LS's tail pipes shaking!!! In addition, she was belching a little bit of black exhaust! If you were at another fuel island pumping, the black exhaust would not have been visible, but standing right next to the LS and viewing the chrome tipped exhaust shaking, I was able to see the black exhaust (unburned fuel/too rich) coming out.

After about 10 seconds of this missing/misifiring/hesitiation/whatever you want to describe, she (the LS) automatically increased the idle rpm's some, then settled back down to a completely normal idle around 700rpm's, and no visible exhaust, and no misifiring, and nice and smooth idle, and without any codes!!! I thought it was really strange, but was just relieved that she cleared up on her own, as we were in the middle of this 12 hour drive!!!

Guess what happened at the next fuel fill-up? Same thing. I got the same hesitation, same slight black exhaust, but again, after 10 or so seconds, she cleared up on her own. The good news is she was idling normal again after that 10 stomach turning seconds, and the better thing is that this issue is REPEATABLE.

Guess what happened at the 3rd fill up? Same hesitation and misfiring.

The specifics:

• I always use top-tier premium fuel
• I changed the plugs within the last 25k miles to one of the OEM recommended iridium brands, can't remember if I used Denso or NGK, although I made a thread on here, but I think this issue is irrelevant.
• She has about 155k miles
• The hesitation/stumbling/misifiring is ONLY happening shortly after I remove the fuel cap. I ALWAYS fuel up while the car is idling. (don't need sidebar conversations about safety during fill-ups, etc)
• The LS is still clear of codes!!! (even with the current exhaust gasket leak!)

I know there's not much that can be troubleshot without her throwing a code, but what are some thoughts on the 10 second misifiring/hesitation at idle, ONLY AFTER removing the fuel cap? This is obviously related to the fuel system, but exactly what related to the depressurizing when I remove the fuel cap while idling?

Thanks for all/any ideas, as we are leaving for the wedding at Graystone Quarry in Franklin TN, just outside of Nashville!

05ls430518

iTrader: (1)

Your making a giant hole in a sealed system thats why it gets really rich while your car is running the evap system runs a check every few seconds to see if there are any holes in it and by removing the gas cap your creating a huge "leak". The car is sucking up all the vapors and its making it run richer hence the black smoke.

jimbosr1

Try turning off the car the next fill up and see if it does it....

imdking

iTrader: (1)

Turn the car off when you pump petrol.

rkw77080

So the long-winded explanation is as follows...

For safety, the fuel tank and pump is located at the opposite end of the LS430. The fuel pump delivers fuel to the engine bay continuously at the proper pressure, and whatever amount of fuel not consumed by the engine is returned to the fuel tank. Temperature of the returned fuel is typically warmer and more vapor is generated within the tank while the engine is running.

The Evaporative Emission Control System (see diagram below) and charcoal canister are there to handle the fuel vapor 1) back into liquid via By-pass VSV to the tank; 2) fuel vapor via EVAP VSV to the air intake plenum; or 3) air via CCV to the air cleaner box.

The fuel filler cap is designed to contain any fuel vapor to escape out to the atmosphere, but allows air to enter the tank to fill the void as fuel is consumed.

By opening the fuel filler cap (while the engine is running), you are altering the pressure reading within the fuel tank which causes the ECM to send to wrong signal to the throttle body and various VSV's and CCV. This is the same condition that can cause the ECM to register the 0441 DTC.

iriz

Just curious - what is the upside of idling when refueling?

05ls430518

iTrader: (1)

Damn everything you post is pure eloquence hahaha

imdking

iTrader: (1)

LS430inDE.

The upside is less wear & tear on the starter & battery. And to be honest, I find it hard to believe that 100% of the folks on here shut their engines off when refueling? Sounds like I need to start another thread.

Also, on a long drive like this (12 hours 1 way, and pulling off the highway where the speed limit is 70mph, yet we were cruising for literally hours at 83mph,) I feel it's better for the car to idle versus shutting the car off after it's been running hard and long, for hours, at speeds between 75 - 85 mph. Do Formula 1 drivers or NASCAR drivers stop their engines when fueling up?

And why would this just start now? I've refueled while running since I bought her in 2009, and she's never hiccuped while getting pumped!? As a matter of fact, NO car I've owned or driven or fueled up ever did this?

I believe there's a little more to the story. On the ride home, I removed the gas cap and waited and waited and waited, but didn't get the bad idle. The bad idle occurs actually about 15 seconds after actively pumping her with the fuel.

I appreciate everyone's comments and informative pictures, but I'm not so sure there isn't something else going on. Like I said, I've never experienced this latest trick, ever, since new to me in 2009.

Funny footnote....on the ride home yesterday, at the next fuel island over, I heard a lot of liquid splashing noise. WAIT. COULD THAT BE GASOLINE? Yep!!!! Someone was pumping up and the guy and girl were sitting in their tinted up Chrysler 300. A lot and I mean a LOT of gas was splashing and spilled out and onto their car and onto the concrete pavement. If I had to guess, maybe a couple GALLONS. I started yelling and ran over and clicked their pump handle to stop if from pumping. Apparently the 'automatic' shutoff didn't work so well on that pump, lol. The 30-ish year old guy simply exited his car to replace the handle back to the pump. I yelled from my island. "bro--you spilled a couple gallons!!" He didn't say a word and simply drove off.