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So I forgot my car was running
December 21, 2008 6:34 PM   Subscribe

So I left my car running earlier today to warm up the engine because of the sub zero temperatures here in Iowa. And then forgot about it for eight hours. Did I just ruin my car?

I've heard that letting a car idle for extended periods of time was hard on it, or that this'll hurt my starter. Help! It's a 2002 Ford Focus, if that matters.
posted by cellphone to Travel & Transportation (24 answers total)
 
No, your car is fine.
posted by sanka at 6:42 PM on December 21, 2008


Nah. Burn up a lot of fuel, but your starter doesn't care how long your car was running. I'm sure others will chime in with long detailed explanations, but I'm going to stick with "nah, fuggedaboudit."
posted by ZakDaddy at 6:42 PM on December 21, 2008


Doh, missed it by that much.
posted by ZakDaddy at 6:42 PM on December 21, 2008


I loathe when people 'nth' a thing to death, but yr engine is fine, just peachy, no worries a tall.
posted by dawson at 6:55 PM on December 21, 2008


I've heard that letting a car idle for extended periods of time was hard on it, or that this'll hurt my starter.

There are a lot of people that know nothing about cars - these are the people that tell you things like this. It's fine.
posted by Brockles at 6:55 PM on December 21, 2008


as is yr starter & etc.
posted by dawson at 6:56 PM on December 21, 2008


I have a 2002 Focus and I've done this (accidentally left it running 4-8 hours) at least 3 times, and he's ok.
posted by Cat Pie Hurts at 6:58 PM on December 21, 2008


This dude says he's an automotive engineer - I'm just quoting verbatim from his response on Yahoo! answers:

"There is a problem with letting a car idle for too long. It can damage the catalytic converter which can cost £1000 to replace.

The problem comes with the throttle plate. This is effectively a valve that opens and shuts in the intake manifold and regulates the air flow. It is attached to the accelerator/gas pedal and when the pedal is pressed, the throttle plate opens proportionally. When you floor it, the throttle plate opens 100%. However when you don't touch the pedal i.e. let the engine idle, the throttle plate almost closes- but not quite (or the engine will stall). It is only about 3% open. Under these conditions the engine has to act as a pump, effectively forcing air through in order to run.

The lack of air means the engine will be using much more fuel to run (ever wondered why you use a lot of fuel while in a traffic jam?) and this richer mixture can clog up in the catalytic converter.

If you have to leave the engine idling for any length of time then take the car for a blast down the motorway/freeway and let the engine rev to 5500-6000rpm so the unburnt fuel deposits will be blown out of the system- you will see a cloud of black smoke coming from the exhaust. This is a good sign and will hopefully save you the cost of a new exhaust."
posted by billysumday at 6:59 PM on December 21, 2008


Thanks for all the answers everyone. I'm convinced that I have indeed not destroyed my engine.
posted by cellphone at 7:13 PM on December 21, 2008


Billysumday, that explanation makes no sense (I know it's not yours). The engine always acts like a pump, sucking air in. And pulling in air against a closed throttle, while it will creat more vacuum, doesn't make the engine struggle. Not vs the struggle to move the whole vehicle.

However, 'tis true, it may make the thing run rich. But then the secondary O2 sensors will notice this, and pull back on the fuel maps. (and you use a lot of fuel in a traffic jam because you're never using the engine in an inefficient manner - a lot of idling, and never in drive or overdive where you're getting the most mpg.)

I do agree with the suggestion to blow the carbon out of it with a good romp on the highway - all that low-load idling is likely to leave deposits.
posted by notsnot at 7:19 PM on December 21, 2008 [1 favorite]


Pay extra attention for any dash warning lights. The orange Service Engine Soon is usually the oxygen sensor. And obviously if any red lights do happen to come on, stop! So many people think that a red light means 'drive it to the mechanic.' No, it means stop the friggin car. :) Hopefully you're in the clear though.
posted by CwgrlUp at 7:27 PM on December 21, 2008


Well, we had a high of 0 degrees here in Chicago today (low -6), maybe in temps like that it makes more sense to warm up the car even if you're not going anywhere?
posted by Hello, Revelers! I am Captain Lavender! at 7:47 PM on December 21, 2008


If you had done this to my old 1965 Pontiac, which had no electronic engine management - engine management was done with screws on the carb and the ignition - it would surely have fouled its plugs and cylinders something awful, and needed a good highway run to blow it out.

Your 2002 Focus, not so much.
posted by ikkyu2 at 7:48 PM on December 21, 2008


Well, we had a high of 0 degrees here in Chicago today (low -6), maybe in temps like that it makes more sense to warm up the car even if you're not going anywhere?

Er. No. Not at all.


Or, in other words, whatever for?

Billysumday, that explanation makes no sense (I know it's not yours). The engine always acts like a pump, sucking air in. And pulling in air against a closed throttle, while it will creat more vacuum, doesn't make the engine struggle.

Totally agree. The car doesn't run any richer on idle unless it is cold - at that stage a different (cold) map is run.
posted by Brockles at 10:47 PM on December 21, 2008


I used my Saturn '97 station wagon as a portable heated sleeper on occasion - that is, if I got tired on the road in winter, I'd pull into an all-night diner parking lot, adjust the heater for comfort (engine on), and sack out for the night. The car lasted 212 thousand miles.
posted by IAmBroom at 11:14 PM on December 21, 2008


FWIW if you had let it run long enough to burn up every drop of fuel, the plastic bladder in the gas tank would have melted and circulated through the fuel injection system, coating the inner parts of your engine with a thin layer of plastic that requires very expensive things to be done before the engine will run again. (Recently happened to someone I know who forgot to turn off his car for a long time - headlamps of the car were also melted due to the buildup of heat, but this was not in the winter.) 8 hours wasn't enough to do that on a full tank?
posted by xanthippe at 11:22 PM on December 21, 2008


An anecdote from personal experience. I did the same to my car in High School, and to add to it, I actually locked the keys in so I had to get a ride to my mom's work to get her keys. Even with that and my terrible lack of maintence on the car, it was at almost 150k miles when I got rid of it. You'll likely be fine.
posted by Morydd at 6:30 AM on December 22, 2008


Did you run the car out of gas?

If you normally don't let the tank get low, and you just did now, you *might* have sucked up sediments in the tank, which means you'll need a new fuel filter. This isn't a big deal, unless you sucked up enough to clog the filter, in which case, you'll need to tow it to fix it, or do it yourself.

In *truly* cold places -- like International Falls, MN -- they'll leave cars idling all night on the very coldest nights, that being the only way to ensure they'll be usable the next day. Here's a bit from Click and Clack about dealing with *really* cold winters and vehicles.

In short -- you're fine.
posted by eriko at 6:52 AM on December 22, 2008


My car only used half a tank. Go figure! Car ran fine on the way to work. Thanks again.
posted by cellphone at 7:25 AM on December 22, 2008


you *might* have sucked up sediments in the tank

Sorry, but this is another old wives' tale.

The fuel pump is always at the bottom of the tank, because it's bolted there. Any sediments are always at the bottom of the tank, because of gravity (that's why decanting works). Running a tank low on fuel doesn't cause any more sediment to collect at the bottom, because it's all there already.

And, FWIW, running a car out of gas will not melt any plastic "bladders" in the tank, although an enterprising mechanic may be able to convince someone to the contrary. An empty fuel tank is filled with…air. It's cool, its dark, and it's quiet, because the pump has been rendered inoperative. Even if there was a plastic bladder, and a heat source to melt it, it wouldn't get sucked into the fuel system because the engine's not running…it's out of gas.
posted by dinger at 10:02 AM on December 22, 2008 [1 favorite]


Cop cars in the US are designed to idle for long periods. They commonly have extra radiators to keep various parts from overheating.

I think, aside from the ordinary wear of operating for 8 hours straight, a danger would be from overheating. As long as the car didn't overheat, I would check the oil and and gas and coolant to make sure there's enough left, as you did just go for the equivalent of a 200 - 500 mile drive.
posted by zippy at 10:12 AM on December 22, 2008


Due to the need to power auxiliary lights, our works vehicles, which are diesel Toyota Landcruisers, Mitsubishi Shoguns, and Land Rover Discoverys, are routinely left on tickover for hours every day - sometimes 6 hours at a time. There are over 200 of them; they do 100,000 plus miles a year on top of the idling time and don't show any ill effects.
posted by hmca at 6:06 AM on December 24, 2008


Whether a vehicle needs to be warmed up varies with temperature and vehicle. But down past -10F (-23C) you start hitting a conflict. You need enough heat to power defrosters before your own breath is freezing on the inside of the windshield. How quickly you get that heat varies according to the outside temperature, and the thermostat controlling coolant flow through the block. It is highly annoying to have to stop after driving a block or two, to scrape the inside!

I did experience once where I pretty much had to leave my car running in order to not have to idle over this problem, even after having gotten it warmed up once. I don't recall how cold it was! But it was so cold, trains coming to Milwaukee from Minneapolis were delayed because the diesel fuel wouldn't flow to refill the train. I was picking someone up.

I had a Bronco II in those days, and when things were that cold, even the warning chime for lights and keys would sound, um, cold. The seats felt like cloth-covered rocks, too. But, she took very well to snow and ice, and would happily cartwheel down the highway, when things went wrong, and never rolled. And apparently the deer whistles worked, I never hit a deer.
posted by Goofyy at 7:08 AM on December 25, 2008


FWIW if you had let it run long enough to burn up every drop of fuel, the plastic bladder in the gas tank would have melted and circulated through the fuel injection system, coating the inner parts of your engine with a thin layer of plastic that requires very expensive things to be done before the engine will run again. (Recently happened to someone I know who forgot to turn off his car for a long time - headlamps of the car were also melted due to the buildup of heat, but this was not in the winter.) 8 hours wasn't enough to do that on a full tank?
posted by xanthippe


THIS has got to be the most ludicrously senseless paragraph I've read today - and I've been on Fark.

So, according to xanthippe, if you run out of gas, you risk melting your gas tank? And your HEADLIGHTS?

OMG, xanthippe, let me service your car next time it needs work. I won't charge a thing... oops, I just found out that your catalytic intake valve needs a new timing transmission seat. It looks pretty serious, but I can get it done today if you approve it now. Cash or credit?
posted by IAmBroom at 11:12 PM on December 30, 2008


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