How Long should i idle my car from the first start of the day?
I idled my car for 3mins this morning and my friend said i was wasting fuel
He recommended i could drive immediately the oil pressure light goes off(thats like 4secs from start)
Is that True?

Yes, your friend's correct.

Modern cars are meant to be fired up, and driven straight away.
Idling period only applies to old cars.

Idling your ride is not only wasting gas, but poluting the air for me and urself.

I tot cars Run better at higher Temparatures
and i tot idling helps the Mass Flow Sensor (MAF) Adjust for the Ideal mix

icemann:

I tot cars Run better at higher Temparatures
and i tot idling helps the Mass Flow Sensor (MAF) Adjust for the Ideal mix

Cars run mor efficiently at higher temperatures.
But, we're talking between 80 - 98 degrees.
It'll take an idling car at least 20 minutes to reach that temp, but about 6 if being driven normally.

The MAF has nothing to do with the idling / warm-up process, and it will auto-compensate for varying conditions.

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Dont have cat. in my car. i removed it cause  i heard it slows the car down
is that true?
I think i need 2 get i since the world is saying "GO GREEN"
so no catalyst, no long idling

About 30m secs, just enough to get the whole system properly lubricated.

sultaan:

About 30m secs, just enough to get the whole system properly lubricated.

what of valve adjust ments and cam lubrication? how long will that take?
the same 30 secs?

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Friend of mine says his car has someting like a Governor that prevents him from exceeding 100KMPH when his Engine is not Hot Enough
Is that true?

Instruction manual in most modern cars states:

Upon start-up, the car does not need to be left to idle, and should be driven straight away.
Just common sense with RPM - oil takes a lot longer to heat up than water does.

I've delved into, and built many engines over the years, for various applications, and have not seen any significant wear in even a 200,000 mile motor, due to a lack of idling before drive-off, when cold.

And believe me, most of my clients drive their cars like they stole 'em - i.e, hard!

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so u are saying the idling is for the ATF and the removal of the Nitrous oxide in the combustion chamber?
Can agree with the idea of idiling 4 the ATF cause i get irregular Gear changes in the morning

@ivvie
Can u explain derivation of Von Mises Stress Equation for me?
and the whole idea of it
i have an idea of tensile stress and Yeild behavior of metals, so u can start from there

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@ivvie @siena
please help
my 2000 nissan maxima, stops when i am at a traffic stop
a mechanic had to raise the idling speed to just above 1,000 rpms
it stopped the switching off, but the engine is now noisy and consumes more fuel
also the change in gears on the auto transmission aint smooth
my battery is fine, as someone recommended i change it

what should i do
please advise

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Increasing your idle speed is a no no , get you another mrchanic if you can get back to original setting.You do not need to mess with the throttle positio n in these newer cars because the ECU will adjust automatically(your mech is still stuck in caburator era engines)

I know your check engine light is on right now, so use a t-25 torx screw to remove the IAC and clean it fluctuating idle speed is usually caused by dirty IAC(google it). When was the last time you changed your engune oil? Change PCV valve too if you can.

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@babatosan
Try your service your injector first. Have u changed your Engine mounts/seats recently? u may have the wrong mounts
also check out  https://www.nairaland.com/nigeria/topic-161742.0.html

My car manual says not to idle the car. Drive off immediately.

@sultaan
changed my engine oil a month ago
what should be the ideal rpm for a nissan maxima?

@icemaan
i have not changed by engine mounts
almost did that a week ago
when i observed the engine block jerks foward when i put it in drive
the mec says it may be connected to the raised idle rpm

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Read this and decide what's best for you. Personally I warm up engine for few minutes before driving off.

The reason that engineers recommended the "drive away" warm-up, as opposed to allowing the engine to warm up at idle was that the faster the warm-up, the lower the build up of harmful condensation within the engine and exhaust systems. So, if you are only going to drive a short distance, you (your car's engine, actually) are better off just driving away after a very brief (30 seconds or so) warm-up, thereby allowing the engine to warm up quickly, and minimize the amount of harmful or corrosive condensation build-up, before shutting down. The majority of the engine wear occurs immediately upon start-up, no matter whether you drive right away or sit and warm it up.
Your engine will incur less frictional wear if you let it warm up at idle (at as low an rpm as it will run at) than if you just drive away. However, if you slowly warm it up at idle and then drive only a short distance before shutting down, the condensation formed in the crankcase (which didn't get a chance to evaporate/boil-off during the short drive) will then work it's mischief. This is the main reason that more frequent oil changes are recommended, by manufacturers, during cold weather months; to get rid of that condensation.
So, if you want to "drive right away", not only should you keep the revs down (but avoid lugging, at all cost), but you should keep the engine load / throttle opening very light. If you drive a cold engine, right away, under high load / high throttle settings, your engine will wear very rapidly indeed.
A "static" warm up is good, provided you are going to drive the car long enough for the condensation to evaporate / boil-off, before reaching your destination. Personally, on puma, I use a combination of the two. I let it warm up, at idle, for a few minutes at as close to 1000rpm as I can manage (usually it's between 1200-1500), then drive away very gently for the first several miles, until the oil temp gauge clears the left green "spot". Of course, I live in a rural area, where I can do this without getting in everyone's way. Those of you in built-up areas, with lots of traffic, probably won't have the luxury of allowing the engine to come up to operating temperature, before you might need to use a heavy application of power. In other words, no one's situation will be exactly alike, so, we all need to do what suits our car's needs vs. traffic and weather conditions to keep engine wear to a minimum.