Some of you might have read my recent post about the radiator/cooling fan/cooling fan clutch replacement fiasco. That was completed with audi-parts that I was able to find wholesale (thankfully... though it wasnt THAT much of a difference price wise). I just got the car back on Thursday and after getting behind the wheelwas once again reminded of why outrageous service costs just might be worth it on an A8. The car, simply put, is a wonderful piece of machinery.

On Saturday night, however, I was using more expletives to describe the vehicle than seen in my above description.

Here's the story:

Got out of work at 9:00pm on Saturday and the car (1997 A8 4.2 Q w/88.6k mi) hesitated to start (cranked a couple times before firing up) but did start on that single turn-of-key. Drove it (on highway @75 mph) about 2 miles to pick up my girlfriend, then drove it 3 miles to ruby tuesdays for dinner.

We were atdinner for about an hour. Got out around 10:20pm. The temperature outside, by this time, was a few degrees above freezing. The car wouldn't start. Everything powered-on (Steering wheel, lights, radio, etc...) and it was cranking, but it wouldn't fire up. The car had half a tank of gas and was on a slight incline, but the engine was on the lower end of the incline and regardless, a half of tank of gas shouldn't be lower enough to make fuel pressure on an inclide an issue either way.

I got it towed and today the service guy went out to check on the car. Fired up with no problem. He tried a few more times and still no problem.

At this point, I'd rather not have the car leave my girlfriend in the cold again, so I'm hesitant to just pick it up. Any ideas about what could have caused the problem then suddenly dissappear?

Thanks everyone.

-Joe

 

One of your crank sensors is toast. There is two total, one for cranking and one when the engine is running, replacing both would be a good idea. They are around $100 a piece a the dealer.
Coolant temp sensors can also cause this issue but the crank sensors on the D2 A8's are much more common.

 

I read a previous post of yours when the car was starting but shutting down quickly after starting. In my case, it wouldn't start at all. Also, I've been driving the car all evening and I've had no starting problems. I spoke with a friend of mine and he said that during the previous service they might have disconnected the battery and so the Mass air might have had to be reset, and that it might have not have reset properly by then, thus causing some malfunction that prevented the start. Could this be the case?

 

The previous post you read was probably about the immoblizer anti theft function, yours doesn't have that.
The mass air sensor won't cause the engine not to start, it may run like s*** until the computer adapts but to the sensor malfunctioning. If it happens again and there are no fault codes buy both of those crank sensors. If it doesn't happen again then the hell with it.

 

"If it doesn't happen again then the hell with it. "

haha well said. Thanks for all of the advice.

 

Sounds like the G28 sensor. It costs ~$150 and is a 10 min job. All you need is a (I think) 7mm allen. Worse case it could be the fuel pump but it definately sounds like the G28 engine speed sensor (or sender).

 

Kinda weird but try replacing the colant temp sensor as this does creat eratic starting some type of safety feature or soemthing replace that part first it cost like 30 dollars or so

 

Thanks for the additional responses... it's been starting for about 2 weeks now without a problem, and then it did it to me again this morning after a cold night of about 18 degrees F. I gave it half an hour and then it started after a couple of cranks. Since the last time, there were no problems, and luckily this time it started up just a little while after I originally tried. Still made me late for work though.

Does this still sound like a crank sensor issue or is it possibly the coolant temp sensor as "missinglink" suggested? By now, I think the cold has something to do with things, if that helps.

 

It might just be a fluke with the coolant temp sender, temp senders usually show thier ugly head when the engine is hot, plus its not a known problem on the A8. But being only a $30 sensor its not a bad sensor to change anyway because it has a small o-ring under it that could leak over time.
The crank sender is more likely which ARE a known problem on the D2 A8 so i would replace that ASAP or you might get stranded somewhere. There are two of them so get the right one from the parts department.

 

Hello again everyone,

First I'd like to thank everyone again for the advice to this point.

My tech is telling me that there are three different coolant sensors (one on the radiator, two on the block). Is there a particular one that would be causing the startup issues? I'm bring the car in for them to check on the sensors all-around tomorrow. I did just have the radiator, fan blade, and fan clutch replaced, and the car NEVER had this problem before the replacement of those parts, which has me hopeful that it'll be the nice cheap part that has to be replaced or perhaps just properly seated... and i do remember that a couple days after the radiator replacement, the in-dash computer blared at me about coolant temp (one of the PULL OVER IMMED. sort of blares), but there was no problem. I chalked it up to those colling components being new and as a fluke, but now it makes me wonder more about the sensors.

Anyway, just wanted to see which particular sensor is the one to look at and see if everyone thinks i'm heading in the right direction.

Auditech, if this doesn't work then the next try will be the crank sensors.

Also, the car had trouble starting sunday morning but since sunday afternoon to today hasn't had any problems, so this is definitely an intermitent problem. Strange.