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Discussion Starter #1 (Edited)
My car ('01 AVH 2.0 auto) starts good usually within 8 engine revolutions when engine is cold. When engine is hot, either it takes 2-3 revolutions to start and the engine shakes wildly, or it takes 2-3 revolutions to be stuck and needs a restart.

Throughout the year I have constantly obtained code P0321/16705 Engine Speed Sensor (G28): Implausible Signal Intermittent (yes) for at least four times: 12/31/2012, 2/10/2013, 3/18/2013, 1/7/2014. No pending codes were obtained. Another constantly appearing code was the one for coolant sensor, and has gone ever since I changed with the green coolant sensor.

In previous troubleshooting [last 3 paragraphs, jfoj], [starting from paragraph 5, jfoj], we have suspected a lot including a bad crankshaft position sensor, and as situation did not go to bad we just waited and saw. I feel perhaps it is time to make a more conclusive guess and start to replace something, e.g., the crankshaft sensor?

Thanks in advance!
 

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waterworld,

Can you explain what you mean about clicking when starting?

I read your cold start issue with the ECU error and you mentioned it took 12-13 clicks to start the car.

I use the following terminology.

On a normally operating car, when you turn the key, the engine "cranks".

After a few moments "cranking" the engine starts and runs.

Clicks to me means when you turn the key the engine does not crank, there is a click and only a click, but no cranking or starting.
 

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Discussion Starter #3 (Edited)
Ah... thanks for mention the terminology issue...

Let me restate my idea with perhaps better terminology:

Hot start: when I turned the key (click?), the starter tried to turn the engine (crank?), after 12-13 (spikes?), and the engine eventually fired/started, wildly.

Cold start: one click, less than 8 (spikes?), the engine started smoothly.
 

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Ah... thanks for mention the terminology issue...

Let me restate my idea with perhaps better terminology:

Hot start: when I turned the key (click?), the starter tried to turn the engine (crank?), after 12-13 (spikes?), and the engine eventually fired/started, wildly.

Cold start: one click, less than 8 (spikes?), the engine started smoothly.
Still not following, what is a "click"?

What is a "spike"?

Turn key, could car less what noise is heard inside car.

If the engine does not crank immediately when the key is turned, explain this.

Click is a noise from under the hook, engine does not crank. Only a click or clicking from under the hood, usually when holding the key in the start position.

Engine cranking, starter is turning the engine, sound heard before the engine starts.

"spike", never heard or used this term.

Maybe a video is needed?
 

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Discussion Starter #5
Haha, I've never been so stupid :rolleyes:

Now rephrase:

Hot start: I turned the key, the starter tried to turn the engine, after hearing 12-13 clicking noise from under the hook, and the engine eventually fired/started, wildly.

Cold start: I turned the key, within less than 8 clicking noise from under the hook, the engine started smoothly.

This one, to me there are 3 clicking noise.

Thanks for your patience :D
 

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Discussion Starter #7
Now I see the difference between click and revolution, thanks jfoj!

Here's my plan to tackle the potential problem of the camshaft position sensor:
  • First, ensure fuel pressure and voltage supply is not a problem.
  • Second, use an oscilloscope to check the waveform.
I will probably do it in spring.

For now, I will change the crankshaft sensor to see if condition gets better, as the code P0321 may also be triggered by the crankshaft sensor and it's fairly easy to replace it.

I ordered a Bosch crankshaft sensor several days ago from Bosch on Amazon and it was only $58 with free shipping.
 

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Fuel pump/pressure pretty easy to rule out with a fuel pressure gauge, just check the static pressure after shut down and make sure it holds the specified value for the 20+ minutes or what ever the spec is. Also make sure the fuel pump is priming when opening the door.

If the problem is a fuel pump, you may be able to cycle the key on and off 3-4 times before starting the engine to see if it cranks over less.

Since your crank sensor is in question, probably replace this first, then see what happens.

Cam sensors on the BMW's get soft and sloppy after 8+ years, they work, but can cause issues, many times you just replace them as PM. Not sure if the VW is the same design/manufacturer, but I would get they may be?
 
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