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

New cars have stop-start system (even though this has been available for a long time). My question is: why are car companies emphasizing shutting the engine down at a traffic light, rather than making the engine run at close to zero RPM (but certainly not zero) at idle speed using the car's ECU?My idea is that the car engine keeps running, and when the driver releases the gas pedal, the engine returns to a very low idle speed. In the manufacturer's current scenario, when the engine shuts down, the battery power is used and can put strain/stress...Read more

engine - 2002 Mercury Mountaineer V8 4.6 2W Drive

While driving on freeway going 75 MPH using cruise control, my engine stops running. I still have lights and power but no power steering or power brakes because engine was off. I put it in neutral and coasted off freeway and into gas station. Tried to start it but it would only click once. Took out the alternator had it tested and it failed, so I replaced the alternator. Tried to start it and only hear a click, even with jumper cables it would not turn over. Any ideas what might be wrong?I had my battery tested it is good....Read more

engine - Poor battery condition, replacement required! Or is it?

I drive a 2004 VW Passat B5. Recently, my insurance company came round to fit a black box to my car as part of the terms and conditions of my car insurance policy. Whilst they were doing this they had to visually check the condition of the car, as well as check the state of the battery.A concern that they had to raise on the report was that the battery was in poor condition and that I should consider getting it replaced. If I don't, they said the car may not start reliably in cold weather.I saw the following reading:REPLACE BATTERYBattery State...Read more

Why do engines run badly below the normal idle speed?

When the engine speed in my petrol car drops below about 650-700 RPM - the normal idle speed - it starts to shake and judder. This could be because say, I didn't give enough gas when pulling away.Why does it run really badly and shake?Also, what determines the idle speed in design?EDIT: I want to know why engines run badly when the idle speed is lower, and how the idle speed of an engine is determined when it is designed, not why it stalls....Read more

engine - Electric water pump control

Electric fans are now common on cars, both aftermarket and stock. The advantages in horsepower, faster warmup, and hence emissions are well documented elsewhere. The same reasoning can be applied to justify an electric water pump. Is there as much to gain as what has been achieved with electric fans?Should the water pump start spinning when the thermostat opens?Could the thermostat be removed and the shutting down of the pump be relied upon to stop water being cooled by the radiator when the engine has not come up to its recommended operating t...Read more

manual transmission - Problems with Turbo Engine of Audi TT 1.8L 2005 150BHP

I bought this car a couple of months ago and last month had a major issue, the car just stopped driving! I called the AA who told me it was the timing belt. I got towed back home and took it to my mechanic (thankfully my next door neighbour) and he fixed my car after about 3 weeks. I'm not too sure what he did, but he ordered a lot of new components including timing belt, valves, etc. I've had the car back about a week and a half, and yesterday morning on my drive into work I noticed a weird high pitched "wooooooo" sound when accelerating, my w...Read more

engine - What’s wrong with my truck

Hi all I have a 08 Silverado 5.3 it has been a great truck but recently been giving me problems. I have a tester and it says I have codes p0036 p0054 p0140 p0141 p0300 p0455 I just recently changed the spark plugs and even before I changed the plugs it was shooting these codes any idea would be greatly appreciated. Also the stabilitrak off service traction control message shows on my dash....Read more

engine - Idle sometimes too high (BMWM50B25TU)

Yesterday I had to drive a lot and after 100 miles I noticed that the idle won't go below 1500 rpm (should be 600) on my 1993 BMW 525i (euro model), except when I drove slowly in a high gear. This morning all seemed to be OK (only did a 5 miles trip though), maybe the rpm fallback was a bit slower than usually when releasing the accelerator.On the other hand, earlier before I had to put some extra pressure on the accelerator to set it off from the top, unpressed position. Now it moves smoothly even from the top position. Could this be just beca...Read more

Mazda 3 2004 Engine Revving when car not moving

I recently noticed when my car comes to a stop engine running and ac on the engine revs as if it wants to move forward. The rev isn't huge. When i am in traffic and holding down on the brakes, if i release the brake without pressing the gas pedal and allowing the car to roll forward on its own the car begins to rev.I took off the ac but this didn't solve the issue. What i did was turn the engine off and turn it back on and it stopped. The problem is not noticeable as i start the car only when i drive for 30 minutes or so.I am not sure what can ...Read more

starting - Engine repeatedly dies at shorter and shorter intervals this cold morning, finally won't start

I have Pontiac Grand Am 2004. It's been needing some regular maintenance, but other than that runs mostly fine. When I went out to start it this morning, it started fine. I went to start brushing snow off of it, and then (about 30 seconds after starting), it sputtered and died. I thought it was probably nothing, so I started it again. This time stayed alive for about 15 seconds. And each time I tried to start it afterwards, it would run for less time. Now, it won't start. The way it would die is it would just lose RPMs, down to 500, until I wou...Read more

engine - Car vibrates when in idle, especially with AC on

A few months ago I hit a curb with my automatic 2013 Honda CVR (don't drive tired). Since then, my car vibrates enough to make me nauseous whenever it is not moving. I got it checked, they said it is most likely caused by a little bit of a bend in the frame, though the frame itself doesn't vibrate much, instead the engine shakes very visibly. After driving it for a few months I've found some other symptoms, and since I know little about cars it would be great if anyone could use these to give possible causes! The vibrating gets worse wheneve...Read more

engine - Toyota camry 2003 , 2azfe - 2.4 L , vibrates at idling & does not accelerate properly

Recently I sent my Camry to the workshop as there was a blown water outlet pipe, and was told that the head gasket was damaged too. These were then replaced, and I took delivery of my car. But my problem seem to have increased as now the car/engine vibrates on idle when in neutral, and sometimes the rev goes below 500 rpm (that too while driving) and the engine dies.Before sending it to the workshop, my car used to accelerate very well and was fun to drive, but now, there are times that there is no proper pickup/acceleration, and sometimes it j...Read more