ALH strange stall issue at running temp

Hello all! Looking for help with a stalling issue with my ALH, been driving me nuts like a pirate with a wheel in his pants.

Itsa manual w 196K on the clock. Cold start is fine, cranks and turns over fine, but once the thermostat kicks in to circulate the coolant for regular running temp, she stalls... UNLESS i have the foot on the accelerator. only stalls at or close to idle. Now get this, it will NEVER turn over on the first crank after the stall... 90% of the time it fires up on the second try, other 10% I have to wait for it to cool down to start again. Stranger STILL, if I rev up near red line on that second start, she'll run for a while, even at idle, before stalling again. But it's up to the fates for how long it'll run regularly, but never for very long. I just put a new coolant temp sensor in, no go. Thought maybe it was an injection issue, ran molly purge strait (in front of the fuel filter), twice! Just to be sure, no go. It rarely throws any codes, once I got a G28 engine speed sensor, but if that was the problem wouldn't it give the code each time? And why only at temp? Anyone that has dealt with something like this it would be greatly appreciated where to troubleshoot next? I just got VCDS in case anyone has diagnostic suggestions. I'm starting to think I need a TDI pro, anyone have a reference for a pro in Seattle?

This forum is amazing and I thank you all again in advance for your help on this, y'all have come through for me time and again when I've had stumbles as I try to work on my own vehicle. What's wrong with my trusty TDI???!

You should test you G28 (crank speed sensor). When engine at idle try to swing the G28 sensor wire little bit. If sensor wire bad the engine will stall.( Be Careful the engine is HOT and the engine fans MAY sudden come off!!) It happened to my 2004 Jetta TDI. In my case it always stall at local speed and no check engine light and no fault code.

Hi Chz17, I forgot to mention that I replaced the crank speed sensor about two years ago, so I assumed it would be fine, is this a common wear item? I guess I'll shell out another $40! I still have the old sensor, maybe i'll swap it back in to see if there is any difference before I get a third darnt speed sensor.

Never assume anything......I’ve had brand new parts fail right out of the box.
It it OEM or aftermarket?

I'm not sure, got it from ID parts so pretty sure it was OEM... But I'll get an aftermarket today and try it. Guess it makes sense since that was the only code it eve threw at me.

Have you changed for fuel filter?

tryin2vw said:

Have you changed for fuel filter?

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Yup, about 7k ago, should still be good for a bit longer I think, but if the problem persists I'll change it out as well.

So I took some time yesterday and swapped the G28 crank speed sensor. There was a bit of engine oil inside the fitting hole and on the magnetic end of the sensor, enough to interrupt the signal no doubt. I would assume that not be a place one should find engine oil... possible symptom of a Rear main seal leak? I only drove the car once yesterday after the sensor install and it didn't stall, but the stalling has been intermittent so I can't say definitely that this fixed it until I ride around quite a bit more.

Thanks for your help!

csstevej said:

Never assume anything......I’ve had brand new parts fail right out of the box.
It it OEM or aftermarket?

Click to expand...

--So True! I should have checked this sensor first... Maybe this thread will help save someone elses time

Nothing new it is typical crankshaft failing symptom. First stage of symptoms is what you had, next stage it will die and never start.

Also, think about the coolant temperature sensor.

So the G28 was the problem?

BobnOH said:

So the G28 was the problem?

Click to expand...

As far as I can tell yes. I swapped it out last week and it has only had one day of my commute where it stalled, same as before, started up on second try, but strangely this was after I swapped the sensor and cleaned the inlet hole. But it hasn't stalled since, about 5-6 days now I think...

-Update over a week later,

It was the G28, the stall after I swapped must have been a fluke. Runs trusty as before. Hope I save someone else the time, as said up before, never assume a recent swapped part isn't the cause cuzz it could be. Like I said up before, I changed out the coolant temp sensor as well, and the plastic housing that connects with the brass colored sensor was loose and able to be turned and moved, I forgot to add that detail earlier. So it's possible it could have been a combination of the two sensors, but it only operated properly after the G28 was replaced.

Nice, thanks for the update!