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24 votes

How slow ( not zero) can a car engine run without hurting engine and saving on fuel

You are right in the thinking of using less gas and that's exactly what the purpose was to have the start/stop feature. The main goal of doing it (at least here in the States) is for zero fuel ...
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20 votes
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How slow ( not zero) can a car engine run without hurting engine and saving on fuel

The oil problem You can run any engine speed you want as long as you keep the oil pressure up. Because of the impossibility of getting a roller bearing down a crankshaft, engine bearings are "...
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12 votes
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How does the transmission not strip itself when applying the brake?

The somewhat longer answer is that the device that makes what you're asking possible is the torque converter. This device is a pair of curved blades setup as an impeller, and a turbine. The following ...
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11 votes
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Why do engines run badly below the normal idle speed?

The engine does not rotate smoothly. The crank shaft is actually constantly speeding up and slowing down. This is most easily seen in a single cylinder engine. The power stroke is the only time the ...
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10 votes
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Is manual start/stop good on older cars?

I work for a fleet delivery service. Due to safety regulations all vehicles must be shut off at every delivery point. This equals up to 150 stops a day. The starter motors fail with regularity. In ...
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8 votes
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Do you need a charged battery for a car to Idle?

It sounds like there is an issue with something in the vehicle after it goes from open loop (before sensors are used to run the car) to closed loop (where the vehicle starts using inputs from the O2s, ...
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8 votes

How slow ( not zero) can a car engine run without hurting engine and saving on fuel

The engine needs a minimum rpm to idle smoothly - a v8 can idle smoothly about 500to 600rpm but a 1 litre 3 cylinder needs around 700 to 900rpm... It is not the companies that really decided to do ...
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7 votes

Idling motor and running AC for 4-8 hours in 100 degree heat?

It shouldn't cause the vehicle any issues. Realistically, all you'll be doing is burning fuel. The wear will absolutely be minimal, mainly because at an idle, there is very little stress put onto the ...
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6 votes
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Yamaha Seca - Motorcycle Idle problems

More than likely, you have an air leak If you haven't cleaned out and rebuilt a bunch of 4 carburetor banks in your life there is a good chance you have accidentally created an air leak in the system....
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6 votes

Engine start is OK but dies when applying throttle

The triple carbs were serviced 2019. I have had this 4 years and only managed 1000+kms every year (very poor for me). It's not always clear what "serviced" means. But for a bike this old ...
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  • 9,429
5 votes

How does air get into the engine with a bad IAC?

In most electronic fuel injected vehicles, there is more air getting through than what the IAC provides. This can happen with either holes directly in the throttle plates or by having them partially ...
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5 votes

How does air get into the engine with a bad IAC?

When the valve is 'closed', it won't completely block the airflow, otherwise, as you note, the engine would choke and stop. Therefore, even if it's stuck in the closed position, some air will still ...
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5 votes

2001 Ford Explorer High Idle

The P1506 code is an idle air control overspeed error. From autocodes.com: The P1506 code means that the engine idle is out of factory specification. Sometimes the Idle Air Control (IAC) may have ...
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  • 5,225
5 votes

Car dealer taking more time to repair. Is it ok to leave car idle for long time?

Cars don't like to sit. There is an inside joke among mechanics, they call degradation due to sitting "lot rot". The biggest impact to a sitting car is the rotors. They rust. Rotors rust even ...
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5 votes
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Is it bad to idle the car for 5 min or restarting the car?

As long as the vehicle is well maintained.. turning the engine off, or leaving it running would not really make any difference to engine wear and tear. Well unless this was being done 50 times a day ...
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  • 5,022
5 votes

How slow ( not zero) can a car engine run without hurting engine and saving on fuel

From physical point of view, lowering the RPM means that you need to store the energy required to keep the engine running (and overcome friction) with a smaller angular speed. And the kinetic energy ...
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4 votes

Fast Idle and High Fuel Consumption

I think you need to do a throttle position sensor recalibration (reset). (NOTE: I will post several different adjustment versions. I believe the top one is what you need (for a K8 engine), but will ...
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4 votes
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Big motorcycles at stop lights; why do they keep blipping the throttle?

Mechanically, it's a bit of a throwback to carburettor equipped bikes - my motorbike, for example, can be a little bit unforgiving when it's cold and it's not nice to go to pull away and have the ...
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  • 379
4 votes

Car stored for 6 months shows low oil level after 300 miles

The oil level is not going to decrease due to it sitting for six months unless a seal went bad. It would appear to me you have an oil leak somewhere. This doesn't mean you are going to have low oil ...
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4 votes

A/C Temporarily Cures Low, Hiccupping Idle

Your CPS code won't explain the hunting idle; the symptoms point to a lean air-fuel mixture: it doesn't stutter at low idle with the engine cold because the fuel management is designed to enrich the ...
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  • 39k
4 votes
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A/C Temporarily Cures Low, Hiccupping Idle

When the throttle body becomes a little worn, it is possible for the butterfly valve to close too much for a steady idle engine speed. The ECM then tries to compensate by opening the IAC more than it ...
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  • 20.8k
4 votes

RPMs jump to 2500 when clutch is disengaged or transmission put in neutral

These are common symptoms of an split air hose allowing unmetered air into the engine intake. Check all air related hoses for cracks. Hoses include the main air intake, crank case ventilation system ...
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4 votes
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Why Have More Than One IAC Type Device On an Engine?

The manual you linked to explains what they're used for. The AACV is the main idle speed control while the FICD is used to supply additional air to the engine when the AC is turned on. AACV (Page ...
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  • 39k
4 votes

How does the transmission not strip itself when applying the brake?

This is a great question, and the answer lies here: Why doesn't the engine stall out when you come to a stop with an automatic transmission? And more information here: How does a torque converter ...
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  • 13.2k
4 votes
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Idle dipping and rising when headlights are on - not Idle Air Control Valve

Check that your alternator belt is tight and in good condition. Also check that your battery is fully charged and in good health. There is a real possibility that the fault is being cause by the ...
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4 votes

Is a +/- 10-15 rpm idle fluctuation normal?

Completely normal. Nothing to worry about
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4 votes
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TSI engine, shaking at idle

I finally find the reason why my car is shaking at idle when the car at uphill. It was a piston failure and repair cost is around 2000$ and also that failure damaged compressor( which is combined with ...
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4 votes

How slow ( not zero) can a car engine run without hurting engine and saving on fuel

Car companies focus on stop/start of the engine simply because There's a minimum RPM the engine can run at. You can sort of extend it using dual inlet/exhaust variable valve timing, but there are ...
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  • 13.6k
3 votes
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Vibration at idle, much worse after warm

Although, your point about cold engine mounts applies, I would doubt they heat up enough to significantly affect vibration transfer to the interior. Instead, what you might look at is increasing your ...
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  • 550
3 votes

Why do engines run badly below the normal idle speed?

There are a lot of rotating parts in the engine, e.g. shafts, etc. Below idle they enter their critical revolutions, then they start to wobble (Layman's term) and you feel it inside, in some case in ...
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