[jdink]

I was taking my usual route into work this morning (driving about 10 blocks, jumping on the freeway for about 5 min, and then taking my work exit) and right after i jumped on the freeway i experienced a limp mode.

At the time the oil temp was about 2 hairs over the baseline and it happened on my 3rd-4th shift. There was a line of cars in front of me coming onto the freeway (1st-3rd gear) so I wasn't pushing the car at all. Once I was on the freeway, I merged one lane over and then shifted to 4th, at which time I went into limp mode (at 4000 rpm).

At the time, I was reading "---" on my gas gague, and was probably about 15 miles deep on empty. (I've convinced myself I have at least 2 extra gallons in my car and can go another 30+ miles on empty).

My hypothesis is that once the car reached 1/2-1 gallon, the car went into limp mode once it decided that I was using gas at an accelerated rate (4000 rpm). In the past I usually go into the "oh shit i might run out of gas, i'm going to coast as much as i can and not touch the gas" mode so I am thinking that is why i've never had this problem before.

Other things to note:
-Chevron (with techron!) 92 oct
-Procede v2 (no limps before this)
-Tiger is leading by 1 after 2 holes

[1clean335i]

probably threw some misfire faults due to low fuel level.

[NM_BMW]

+1 misfires.

When I get the second low fuel warning there is only 1 gallon left.

[jdink]

Originally Posted by Humtek

+1 misfires.

When I get the second low fuel warning there is only 1 gallon left.

Wait.. there is a second low fuel warning?

[NM_BMW]

Originally Posted by jdink

Wait.. there is a second low fuel warning?

Yea. The first one comes on about half way between empty - 1/4 of a tank. It stays on for a bit and goes off. Then you get a second warning when your at the last notch or 1 gallon left of fuel and the warning stays illuminated until you gas up.

[cycler]

Ive actually driven to see how many miles i can get without refueling like in the episode of seinfeld LOL. But ive only gotten it down to 2 miles till empty. chicked out to go any further even though there are lots of stations on sunrise highway

[jdink]

Just called my Service Advisor and he confirmed the cause of the engine fault code (not because I didn't beleive you guys! But i prefer to keep them updated when I throw a code so they know exactly why incase it shows up later)

Anyways, can anyone explain in somewhat technical terms what happens in the misfire? I'm pretty dumb when it comes to this stuff, so it would be nice to use this as a learning experience

[AJerman]

I don't understand why some people run their gas so low. I typically fill up at my earlier convenience after a quarter of a tank or so. No point in getting it ridiculously low, because inevitably you'll get stuck about to run out and in a big hurry to go somewhere. Plus, I don't see much point in increasing the risk of sucking up crap from the bottom of the tank when it runs nearly empty.

[cycler]

Originally Posted by AJerman

I don't understand why some people run their gas so low. I typically fill up at my earlier convenience after a quarter of a tank or so. No point in getting it ridiculously low, because inevitably you'll get stuck about to run out and in a big hurry to go somewhere. Plus, I don't see much point in increasing the risk of sucking up crap from the bottom of the tank when it runs nearly empty.

I always fill up at a 1/4 tank no matter where i am but this a one time thing because my friends and I were talking about that seinfeld episode when i had a 1/4 tank left so we just drove around and ran our erands until it got down to 2 miles left.

[jdink]

Originally Posted by AJerman

I don't understand why some people run their gas so low. I typically fill up at my earlier convenience after a quarter of a tank or so. No point in getting it ridiculously low, because inevitably you'll get stuck about to run out and in a big hurry to go somewhere. Plus, I don't see much point in increasing the risk of sucking up crap from the bottom of the tank when it runs nearly empty.

Since I get 15 mpg I go from quarter of a tank to empty pretty quick... I typically try to fill up at one or 2 different gas stations in my area (Chevron's) and both are on my way to work. Since it was the weekend and I figured i'd just wait until monday morning to go fill up since I know I can go at least 20 miles on empty.

Is there really a risk of sucking up crap from the bottom of the tank? Wouldn't it pull from the bottom of the tank first anyways? If so, maybe i'll change my habits, otherwise i'm comfortable driving around on empty if I know i will pass my regular gas stations sometime soon. (rather then go out of my way)

[NM_BMW]

Even if you had some "stuff" in your tank it will usually get filtered at the fuel filter. That's what the filter is there for.

BTW, I love that episode of Seinfeld. "TWIX!!!!!!"

[Gen_E92]

i got a CEL as well with low fuel and hard driving...the first time the car has around 15 miles left, then the exhaust note sounded like the engine is not sucking in fuel, i shut it down and restarted again, problem is gone but CEL still there...second time that happened there're still 1/4 gas left

[BoostedBMW]

Originally Posted by AJerman

I don't understand why some people run their gas so low. I typically fill up at my earlier convenience after a quarter of a tank or so. No point in getting it ridiculously low, because inevitably you'll get stuck about to run out and in a big hurry to go somewhere. Plus, I don't see much point in increasing the risk of sucking up crap from the bottom of the tank when it runs nearly empty.

Also with an in-tank fuel pump you will end up running it harder since the fuel itself is what cools the pump. Of course no one can say with certainty just how much of an impact that will have on the pump over time, but making any electric pump run hotter can't be a good thing.

[StarrDlux]

yeah you also must understand other items such as water don't necessarily mix with water (like water and oil). this very expensive pump is designed to be cooled and lubricated with gasoline and not suck up junk (that the fuel filter thus gets clogged up with).

i think the lowest i've gone is 14.2 gallons refill on 335i sedan which is about as close as i would ever feel comfortable going down to. i can understand though with 16.1mpg how easy it is to run it low.

even though a car is warranted and the pumps are known to die on their own, i'd do what you can to keep the car off the side of the freeway it kind of sucks if you've ever had to experience that.

misfire is multitude of sources but the answer is that the ecu felt combustion did not occur. Most ecu's use a combination of knock sensors and the speed of the cam sensor to detect misfires.

On american cars with huge 110 to 112lsa cams that idle like a jalopy you have to disable misfire codes since they essentially constantly misfiring. the amount of oil contamination from constant misfire and stress on the crank (the motor really isn't designed to run with less than 6 cylinders in our case) just not good mojo.

i carry 4 spare coilpacks on the audi due to the very well known nature of coilpacks failing.

modern ecu's shutdown the fuel on a misfiring cylinder if possible so it doesn't burn it in the exhaust (turbo) and char-broil the cat.

i gotta say this N54 motor is pretty rough on the edges. i've never in my life had a car with 1000 miles on it have so many hard starts. Makes me wonder if that is the ominous sign of the fuel pump going out or just some bad programming..

how ghetto is it to have a 50K car that has to turn over 4-5 times about every 3rd day to kick off. if my audi did that i'd be doing serious investigation even though it has 104K miles.

but my car was also one that threw random oil low codes and blew oil out the right pipe for 10 minutes after i parked on a decline the day i got it home. I think thats about when i figured this is a definite lease-turn-in.

[NM_BMW]

Your pump might be failing. My car only takes one crank to start up.