Now this is a weird issue, I had to do a lot of driving over the past few days without any issues. Well yesterday I went to start my car, and well quite simply put wouldn't start. The starter works, and after a few minutes the car finally starts. However it idled very low and stalled out ( it's an automatic). Again I start it up and if I tap the gas it stalls as well. the idle a cold start is normally 1200 for a minute or two and drops to 900 but it idled at 900 when I finally got it started. I checked it with a scanner and no codes, no cel, but my coolant reads at 236 degrees. My coolant levels were low so I topped them off thinking it may solve the issue, but it didn't and I'm pretty sure it's not my thermostat or water pump as I replaced those two years ago when I did my timing belt. It's an 04 A6 2.7t S- Line

 

how old are your plugs, wires, ignition pack?

Ive also seen some cars crap out if there is a vac leaks. any chance your idle was bouncing a little?

 

Plugs were replaced 15000 ago. the car has 127 k on the odometer so it could be the wires or coil packs, which have never been replaced . but the idle was staying at a constant 900 no real fluctuations.

 

It's probably the coolant temp sensor.

With the symptoms it could also be the engine speed sensor, but considering the temperature reading for the coolant.. I'd start with the CTS.

 

That's something I thought it could be too. I guess I can give it a shot, because that sensor is WAYYYYYY cheaper than any other sensor I've ever replaced lol.

 

Yeah, but it depends on if you need the blue sensor or the green one.

Green one is like $12 and they carry it Advanced Auto. The Blue one runs about $40 or so.

If I remember correctly you'll need the blue one if your OEM connector is square and the green one if your OEM version has the oval-ish shape to it.

The blue one may have a blue connector plugging into it as well, I use the green one and my connector was black.



(Credit to "Justin" for the photos)

 

I second checking on the coolant temp sensors based on your coolant temp reading.

 

Thanks for the tip. I already have a green one in there, so I was under the assumption it would be the same. I guess I'll find out tomorrow.

 

It was the sensor. Little bugger is buried underneath the stupid intake flex-pipe though. Almost took the coolant resevoir off trying to find it, that would have been interesting. I didn't secure it fully, so on a test drive after the repair it popped out *woops*. But once that was done it runs just fine if not better than before. I just never would have guessed that a coolant sensor would stop it from starting, or that the CEL wouldn't come on until the new one was in.

 

I pulled my back in the process of swapping mines -- SO.MUCH.PAIN! I couldn't make any sudden moves for the next 2 weeks without feeling all sorts of ridiculous pain. SMH

Yeah, I didn't get mines fully secured on the first try either because of the O-ring, had to pull off the connector and force it down the with the handle of a screwdriver -- some Vaseline on the O-ring probably would have gotten it into place easier, but I didn't discover the Vaseline trick until I was having issues getting my upper coolant hose back onto the radiator.

As far as the no-start:
Testing the Jaguar Coolant Temperature Sensor
That page explains it pretty well.

Cold starts require more fuel.
Faulty Coolant Temp Sensor = ECU thinks car is warm already and doesn't supply enough fuel.

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Glad you got it sorted. The inexpensive fixes are the ones you gotta treasure on these damn cars, lol.