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10

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 cutaway pictures illustrate this setup: Here is a torque converter split in half for a better view: The way this works is explained really well by a You-...


9

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 engine is under power. The other three phases are completely unpowered. This means that the engine needs to store enough power in something to get it through the ...


8

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 most cases 3 times or more a year. Ignition switches about twice a year, and fly wheels every 2 years. While you won't see this type of abuse,stuff will wear out. ...


6

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, MAF, and other sensors). This switch over usually occurs about two minutes from a cold start-up. I would start by cleaning the MAF with electronics cleaner (...


6

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. Unmetered air will create the symptoms you describe. The giveaway on most lean conditions is the falling idle. It idles high and is getting enough fuel but ...


4

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 include another four depending on your engine.) To do this for your vehicle you need to follow the steps below, depending on whether it is a stick/auto and ...


4

Most likely a stuck A/C VSV (Vacuum Switching Valve). It's supposed to activate to increase the idle when the A/C compressor starts. When it fails you'll have crazy low RPM idle when running the A/C. Normally the A/C VSV is pretty easy to locate for pulling out and testing. Factory repair manual will have the test procedure (normally just apply the ...


4

From some information I have gotten from several Mustang forums 3.8L come in two varieties. An externally balanced and an internally balanced variety was available. Model year 2000 was change year. 1994 thru 2000 were externally balanced. 2000 1/2 and up are internally balanced. What all this means is if you use the wrong flexplate the motor will shake as ...


4

Most likely case is a bad throttle position sensor or a bad air sensor (some cars use mass air flow, some use manifold pressure). This is typically not something that can be seen in codes, but must be identified by comparing sensor data and graphs. Other possibilities could be a vacuum leak, but that would probably throw a code/check engine light. Of ...


4

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 get through. This should result in a slow idle - but of course if the ECU thinks more air is getting in, it will be putting more fuel in, resulting in rough ...


4

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 open (very small percentage). This is still metered air (air the computer is aware of), but it is air getting into the system. Newer vehicles with "drive-by-...


4

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 engine splutter. In fact, an inexperienced rider could easily fall off because of it! And, as you've highlighted, a badly set up bike might have issues idling. ...


4

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 tomorrow morning, but it does indicate you need to keep an eye on the oil situation. What you can do is to check the ground where you normally park your vehicle ...


4

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 AFR while the engine is warming up (aka cold-start enrichment) turning the AC on helps because it induces an additional load on the engine, which makes it ...


4

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 is designed to under normal conditions. This can cause stalling and unsteady idle. There will be a screw on the throttle body that allows adjustment of ...


4

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 EC-GA-117) This system automatically controls engine idle speed to a specified level. Idle speed is controlled through fine adjustment of the amount of ...


4

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 work. With a manual transmission, you push in the clutch to disengage the transmission. With an automatic, that job is handled by the torque converter.


3

The throttle body at this age of vehicle has a real possibility of being 'dirty'. Take off the large hose connecting the throttle body to the air cleaner at the throttle body. If the visible throttle body parts are heavily coated with cruud, then clean the throttle plate and throttle body with a tooth brush and throttle body cleaner fluid. Operate the ...


3

Most modern engines should increase RPM's when the load on the electrical system increases, as the Engine Management system should monitor voltage and identify it being drawn low, so increasing RPM to increase output from the alternator. Even many older engines would do this.


3

If you have done any performance mods they may be contributing to your cold idle problem. Exhaust or air intake mods may put you in a borderline lean condition. You could have a lean idle circuit. This could be an adjustment/calibration problem or a dirty carb. When you open the throttle you bypass the idle circuit and the accelerator pump richens the ...


3

I'd put a vacuum leak or a failed idle speed controller of some type at the top of my list of suspects. Not familiar with a Focus, but those are common problems that can cause those symptoms as a car ages.


3

I don't know of any vehicle (as equipped from the factory) that increases the idle speed to compensate for a large draw on the battery. If the alternator starts bogging the engine down then the computer should compensate to maintain the set idle speed but not make it increase. It's easy to find out if the alternator will put out enough current at idle to ...


3

The ICV (Idle Control Valve) can be cleaned once removed. But, it should *not* cause the vehicle to backfire. It sounds like you're dealing with a large vacuum leak. Here are some things that you should have a look at. After checking for any obvious vacuum leaks around the top of the motor, the Vanos & Crank Case Ventilation System should be next on ...


3

I had the same problem with my car last year, problem only occurred when idling and not while driving. This is why I immediately suspected the IAC. Removing and cleaning the IAC did the trick for me. Hope this will help you.


3

The stalling symptoms could be explained by a fuel pump relay that doesn't like heat. I say this because the vehicle stalled seemingly intermittently, but whenever the car had been running for quite some time, only for it to start up again after a few minutes (allowing the relay to cool down a bit). If the relay is the root cause, the fix would be to ...


3

The battery shouldn't make a difference, providing the alternator is working properly. However, if you don't have a starting problem, that suggests it isn't the battery that is the root cause of the problem - more like something electrical. From the symptoms you describe, it sounds more like a fuelling issue - perhaps the fuel pump is cutting out after a ...


3

It could be that the oil level was low before it went into storage. Upon sitting, the oil will have settled for a few % above low error. When driving the oil becomes distributed around moving parts and resulting in low oil alert. If the oil level drops again now you have added more oil, then suspect leak. If not, its just a very wierd coincidence.


3

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 and vacuum hoses.


3

The reason to use two is a matter of scale. Fast idle requires a high volume of air but the exact amount is not critical. So a big bore with a cheap slow moving plunger is all that is needed. Idle requires a much smaller amount of air but a much higher degree of control than fast idle. A more expensive fast cycling shutter valve is the most common design. ...


3

I have experienced the same symptoms on an engine, where the MAF sensor was giving lower than expected readings. The engine would only run for a few seconds before stalling. A new MAF sensor fixed the problem. I tested my MAF on the bench with a hair dryer and a multimeter. It wasn't until I got a replacement that I could see how low a reading the faulty ...



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