Both Cars Broke Down Today

[footfootfoot]

Alcohol and Gasoline don't mix.

Actually, they do mix, but they taste terrible.

TFIBHAW,TTS

[ZenGum]

"Check Engine!" is like "we need to talk" and "if you don't know why I'm mad, then I'm certainly not going to tell you" all rolled into one.

[footfootfoot]

and this:

[HungLikeJesus]

You need to flip that video.

[footfootfoot]

But then the Audi logo would be backwards

[tw]

Originally Posted by Beest

In modern vehicles is there a separate line for the choke, or is it all done with one throttle.

A choke was how to throw massive amounts of gasoline into an engine that would otherwise not start. A 1930 technology called fuel injection made that and so many other functions all obsolete.

Your injection measures the entering air. Views other parameters. Then spits in the best amount of gasoline required. In a previous discussion (maybe April 2010) with Cloud, one simple control system was perverted so that idle would fail intermittently. Your subjective summary describes failure in the same system. But you have no reason to believe your system failure is a same part.

Problems reported by the check engine light are always easy to find and fix. Your's is apparently more complex because even the check engine diagnostics do not see it.

Engine performs differently when the throttle is fully open verses when closed. Different parameters and sensors cause different amounts of fuel to be spit into the engine. Apparently your intermittent involves sensors that are significant at idle and not significant when the throttle is more open. Without check engine codes, the number of suspects increases drastically.

Sometimes a service bulletin will define this failure. A previous vehicle had the same problems that the check engine diagnostic did not see. Only better mechanics read and learn from these. Some libraries also provide access to them (online) for all manufacturers.

Possible is a significant parameter stored in the computer. And therefore would be identified by a better mechanic or a smarter computer diagnostic. Some dealers may temporarily install a computer to your diagnostic port so that relevant parameters can be collected when the car will not start. Then a human can see what the check engine diagnostic did not.

Information posted that provided useful replies is that it starts when the throttle is not in idle. Expand on that concept to define specifically what is done to make the engine start. Turn a subjective post into something more quantitative. Playing around with the throttle says almost nothing. Details of what is 'played with' will go a long way to isolating an intermittent to a computer subsystem or sensor.

Also relevant are other details such as the angle of the car everytime it does not start? Pointed up hill, downhill, tilted left of right, etc. Engine overnight cold. Or just partially cool? Attitude of the neighbor's cat? How far to the nearest prankster's house?

Biggest reason for no solution is insufficient information and too much information that is only subjective.

Water in gasoline was way down the list among the least likely suspects along with that cat.

[monster]

So the cat is causing the problem? Darn hair gets everywhere.

[Beest]

So, I know you've all been waiting with baited breath..

After a fill of gas I out in the HEET iso plus, I beleive it still complained about starting a couple of times, but after a few days and running through less than half a tank of gas the problem disappeared.
Was it the new gas, did the HEET clear some water, did the injector cleaner additives shift some other gunk? It's not a controlled experiment so who knows, my money is on the water, Zengum get's a cold one.

When I started driving and learned car maintanence cars has a choke lever ot knob to pull out when the engine was cold and push in again when it warmed up. I was told this open a seperate channel to deliver more fuel directly to the pistons.
A quick google says this is not how the choke works in a car, but may be in some motorcylce engines, so I guess I have been misinformed all these years.

[BigV]

Congratulations Beest!

regarding a choke. It works like it sounds. Take your hands a wrap them around your throat. Squeeze. Feel the choke? Yeah. Same thing in a car (motorcycle, generator, lawnmower, whatever). When the engine is cold, it is easier to burn a rich-er mixture of fuel and air. So, the "choke" operates a linkage/valve/butterfly that *reduces* the amount of air that's going into the engine without changing the throttle position. The throttle controls the fuel (generally speaking), so by reducing the relative amount of air the engine's getting, the mixture has more fuel per air and is therefore richer and therefore ignites more easily.

As the engine warms up, this rich mixture makes the engine run poorly, so the choke is "turned off" as it were. The regular mixture of fuel and air is now restored, and the engine's at normal operating temperature and it runs normally.

eta:
I learned via a google search that adding more gas via a separate line or any other method is still called "choke". The same purpose is achieved, a richer mixture for cold operation.

[Lamplighter]

Choke = cut off air
Less air = higher gas to air ratio
Higher ration = more gas

That used to make sense to me

[zippyt]

the choke reduces the air flow so more fuel get used

[monster]

Damn you beest, I canme to post a similar -but better- update. It passed the ultimate test today -I went to that Burger King for lunch, parked in the same spot, and it restarted no problem.