Question: What makes idling so bad?

[ItsuMitsubishi]

I'd like to think I've thought this issue through, but of course someone else just might think of something I've missed...

So what makes idling 'so bad'? Let's assume we've got a garage queen that can't be driven on the street for legal reasons, and let's take the oil out of the equation, assuming engine has a never ending supply of fresh crankcase oil, how does cold starting and say a 75% warm-up negatively affect an engine?

Now how about if half of the cold starts are allowed to reach NOT, and a cooling fan to kick in, and the rest are just to about 50%-75% NOT. Let's say the engine gets a couple neutral rev blasts to blow out any unburned fuel and carbon, are there any other aspects that can cause harm or shorten the engine's life?

 

[Steve S]

People just need something to be bad.

 

[Nick R]

I'm personally a believe in idling is not bad. Otherwise police cars wouldn't last till 200k miles or more When all they really see is idle idle idle idle idle idle idle idle WOT WOT WOT WOT idle idle idle idle idle idle idle idle idle idle idle idle idle idle idle idle WOT WOT WOT WOT idle idle WOT........ you get the idea.

 

[Johnny248]

It is bad because it is more difficult to control air/fuel mixtures on an engine that is not under load. IMO there tends to be excess fuel being burnt that is not required. This can lead to spark plugs not self cleaning, or fouling out plugs and leaving extra deposits on valves, etc. It also prevents the catalysts from reaching optimum operating temperature to do their job.

 

[Mr Nice]

The transformer blew up in our neighborhood about 2 years ago and we had no electricity from about 11 PM. My wife went outside to her Accord to cool off with the A/C since it was a very warm humid night. I thought she would only be there for 30-45 minutes to cool off and then come back inside the house.

When I woke up at 6 AM she was still inside the car sleeping in the back seat with the engine running and the A/C on since 11 PM. When I open the hood the air from the engine compartment was VERY hot and I'm thinking the engine is fried. The temp gauge was where it normally is when driving the car.

I though about immediately changing the oil but then decided to run it for the entire 7K miles.

 

[440Magnum]

With electric fans its not nearly as bad as it used to be, but gasoline engines still don't like idling. The total air flow through the engine is very low, combustion happens at low pressure, so the rings don't seal as hard and the combustion doesn't go to completion as readily, so there's a lot more blow-by and its nastier blow-by too. And its all even worse when the engine is stone cold. Idling once the engine is already at full temperature isn't nearly as bad as cold idling. All that is less of a problem with diesels because they don't have a throttle and the air flow doesn't drop at idle.

 

[hpichris]

Originally Posted By: Nick R
I'm personally a believe in idling is not bad. Otherwise police cars wouldn't last till 200k miles or more When all they really see is idle idle idle idle idle idle idle idle WOT WOT WOT WOT idle idle idle idle idle idle idle idle idle idle idle idle idle idle idle idle WOT WOT WOT WOT idle idle WOT........ you get the idea.



lmao.....No idea why, but your post cracked me up.

 

[JHZR2]

Define warm up? 3/4 of the correct operating water temp? I recently correlated oil and water temp on my car under light driving - when the water was full temp, the oil was just passing 160f, which is not hot enough to drive off furl or moisture from the dump. It took at least 3.5 more miles of light stop and go driving to get the oil to temp, let alone if the car was just idling, that would take 30 min...

Meanwhile, when everything is slowly creeping to temp, all the moisture and fuel is diluting the oil further, so then it is a time at temperature thing to drive it off.

Even if you changed oil all the time, those transient effects are the worst. Remember, it is start and warmup that is hardest on the car, not highway driving.

I'd get some good oil, fill up the tank including stabilizer, and disconnect the battery but put a float charger on it. Then get it road worthy.

 

[JHZR2]

Originally Posted By: Nick R
I'm personally a believe in idling is not bad. Otherwise police cars wouldn't last till 200k miles or more When all they really see is idle idle idle idle idle idle idle idle WOT WOT WOT WOT idle idle idle idle idle idle idle idle idle idle idle idle idle idle idle idle WOT WOT WOT WOT idle idle WOT........ you get the idea.


That's different, cooling issues aside, those cars are idled in a full warned up state, so the only concern is shedding heat. It is the idle warmup from cold iron that is the problem.

 

[mechanicx]

Exactly, probably the main reason idling is considered bad for oil is that oil life is greatly reduced if it is ran at too low of temperature (or too high) and not at operating temperature ~200F give or take. Also idling is a time issue since milage can be low but oil contamination time high. Also oil presure and flow is not as high at idle but on the other hand it does not need to be quiet as high. Some parts still need some degree of "splash" lube like cyl walls though.

 

[simple_gifts]

If you want a muffler full of condensation, idle away....

 

[crazyoildude]

dont forget most Police cars are crown vics with the 4.6 engine one of the best...
Lets see how the new Police fords are going to be hopefully better than the dodge

 

[Ramblin Fever]

I don't know...all I can say is I have a truck I've owned for 14yrs, since new; in the winter time, I *have* to let this thing idle for at least 10min.

Not because the engine has an issue, it's a computer design in the transmission that will not allow it to shift out of 1st gear until the engine is half normal running temp; meaning the computer literally KEEPS the transmission in a low gear forever after taking off and then it nearly slams it into 2nd gear....from that point on it's fine.

Apparently this was a computer design set-up with emission [censored] in mind.

I for one do NOT like the way it makes the transmission force hold this shift and then slam it; so if I at least wait to roll off until the engine is half up to normal temp then the shifts are smooth from the beginning.

Doing it this way since a month after I bought it new, 200k miles ago. Engine doesn't seem to believe it's ever had to idle, if that's supposedly bad on an engine; runs super strong, doesn't burn a lick of oil, muffler is still original.

 

[tinmanSC]

Originally Posted By: Steve S
People just need something to be bad.

+1

 

[Gary Allan]

Quote:
how does cold starting and say a 75% warm-up negatively affect an engine?


Because the engine perpetually lives in the "90% of all wear occurs at start up" zone. You never reach the plateau. Not that it makes too much of an impact, per se~. It's just an expensive way to put wear on an engine- zero miles at a time.

Since it's a trailer/garage queen, it would be sensible to have block and pan warmers and use them for the weekly event before running it. No extra fuel enrichment ..no additive reaction issues ..no corrosive fuel components ..no moisture absorption, you'll be always in the moisture purging stage ..etc..etc.

 

[CharBaby]

One of the things that I have never mentioned here is that I have had many vehicles in my life that were not driven many miles over their life with me. I have had many vehicle that I/we have put many hundreds of thousands of miles on with kids growing up and being involved in travel sports, school events and family vacations and just plain running around and around, even taking the neighborhood kid all over the place with us as a family.

I have had several vehicles that never saw an out of town drive. Local only! Shopping, hardware, autoparts stores, help a friend/family member move etc. I may have put on 90,000 miles in 16 years(less than 6k/yr). Lot's of idling and short trips. Heck!, I would even leave the vehicle running for 45 min in the driveway while I was snowblowing the driveway and completely forgot the vehicle was running. I sometime do this now with our newer vehciles but I try to stay focused.

These vehicles that I speaking about were carburated and nothing special. Due to their long life and low miles I did often replace exhaust parts, brakes and tires. But, nothing ever went wrong with the drivetrain due to idling too long and these vehicles did their share. Idling with the heat or air cond waiting for the kids(or mom) to get out of school or the mall. ATMOF, I did alot of waiting for people!

With low miles and the vehicles being in their teens, there were other problems with the vehicles but, nothing to do with idling. There is nothing better than running an engine on the highway for long distances. Cars that idle often may not run as well as a highway cruiser but, mind didn't really run bad! And I did this with several vehciles while keeping them into their teens.
We're sorta doing this now(again), that it's just mom(wife) and I.

 

[mechtech2]

Originally Posted By: Johnny248
It is bad because it is more difficult to control air/fuel mixtures on an engine that is not under load. IMO there tends to be excess fuel being burnt that is not required. This can lead to spark plugs not self cleaning, or fouling out plugs and leaving extra deposits on valves, etc. It also prevents the catalysts from reaching optimum operating temperature to do their job.


This is wrong or completely opposite of the truth.
Mixture control is much better at idle or part throttle than WOT. Wot is not O2 sensor governed - it is in the computer as a pre set, and is always richer than stoichiometric.
Less volume at idle is less deposits -either plugs or valves.
Etc.

 

[SteveSRT8]

Anyone with a newer car in good shape virtually cannot hurt it by idling, even for extended periods.

I've sat in my Silverado and watched the PCM slowly increase the idle speed because the auto ac wanted more power. Modern OBD II controls are looking at a fantastic amount of data and are controlling the fuel and air much more precisely than ever. This means idling is likely your easiest operation.

 

[antonmnster]

I think there's a substantial difference between idling a car in cold or very cold conditions to warm it up, and idling once the engine is already warm.

If it's warm, it can go forever no questions asked. Unless there's something wrong with your electric or vicious fan.

If it's -10F and you start your car and let it sit there, your engine isn't going to last all that long. If you only experienced FL winters, then you'll have no clue what I'm talking about.

Many cars won't ever warm up in extreme cold by idling. Well, not within the first hour. All my euro cars and even my work trucks simply aren't burning enough fuel to warm up. On the other hand, they certainly are burning enough fuel - and at a low combustion temperature - to create enormous amounts of blow-by and condensation. I've got some pictures of the valve cover from my BMW that's covered in what looks like peanut butter; I live about 1.5 miles from my work and idle a lot. Not an issue in the summer, but throw a Minnesota winter at the engine, and we see problems.

The last winter I had my e36 BMW, I was getting a bunch of CELs because I'd start it cold and let it idle. The O2 sensor kept throwing codes even though it was new.

 

[ItsuMitsubishi]

Originally Posted By: JHZR2
It took at least 3.5 more miles of light stop and go driving to get the oil to temp, let alone if the car was just idling, that would take 30 min...


Yikes, and that's driving. This car never goes on the road unless it's tracked..

Originally Posted By: Gary Allan
Because the engine perpetually lives in the "90% of all wear occurs at start up" zone. You never reach the plateau. Not that it makes too much of an impact, per se~. It's just an expensive way to put wear on an engine- zero miles at a time.

Since it's a trailer/garage queen, it would be sensible to have block and pan warmers and use them for the weekly event before running it. No extra fuel enrichment ..no additive reaction issues ..no corrosive fuel components ..no moisture absorption, you'll be always in the moisture purging stage ..etc..etc.


That would be a good idea now that winter's coming up. After reading all the replies here, I'm starting to reconsider even starting it up every week or two... maybe it's not even worth it just for me to rev it up for the intake and exhaust sound.. perhaps I should fill the crankcase with cheap oil and switch it out to the good stuff when it's time to roll. Sta-bil in the gas is a go for sure.
Originally Posted By: antonmnster

If it's -10F and you start your car and let it sit there, your engine isn't going to last all that long. If you only experienced FL winters, then you'll have no clue what I'm talking about.

Many cars won't ever warm up in extreme cold by idling. Well, not within the first hour. All my euro cars and even my work trucks simply aren't burning enough fuel to warm up. On the other hand, they certainly are burning enough fuel - and at a low combustion temperature - to create enormous amounts of blow-by and condensation. I've got some pictures of the valve cover from my BMW that's covered in what looks like peanut butter; I live about 1.5 miles from my work and idle a lot. Not an issue in the summer, but throw a Minnesota winter at the engine, and we see problems.

The last winter I had my e36 BMW, I was getting a bunch of CELs because I'd start it cold and let it idle. The O2 sensor kept throwing codes even though it was new.


With winter coming up, that's exactly what I could expect. Those BMWs were designed for WOT on the Autobahn, those cold winter short trips must have been torture to them! Even tho this engine has an oil/water heat exchanger, still not too sure how much it'll help.