S8 2001 Engine Starting problems
 

Hello Peeps how is everyone doing?

Im mainly a Jap car guy and new to audi's etc and wondered if you could point me in the right direction in common faults with them. I have a mate who has a 2001 Audi S8 , he is complaining that the car has difficulty starting when hot, when it is cold ie first thing in the morning it starts no problem at all , but once he gets to running temp and turns the car off it wont start it just turns over, He then has to wait like 20-30 minutes for it to start again.

Coolant temp sensor comes to mind but he has taken it to the dealer and they want to change the AFM , engine coolant sensor and the lamda sensor, i find it hard to believe as if they were all shot then the car woudl run like a bag of nails and it doesnt it runs quite good and he says doesnt use any more fual than normal.

Has anyone experianced this or heard of this being a common fault and what the solution was for it , all audi did was read the codes which might have been from memory. Any help is appreciated.

Simon

Bump ****

does anyone have the workshop manual for the 2001 s8 please

I can only assume that the dealer read codes indicating the need to change AFM (MAF?), coolant sensor and lambda (O2) sensor. The MAF could have something to do with it, but often leads to stalling at idle when hot...but not always. Coolant sensor would not likely lead to no start, but if it's bad, it needs to be changed, as do other items.

If those items need changing, it might be a good idea to wait and see if the problem goes away with that repair(s).

I have a Bentley manual on that year/model, but it includes no troubleshooting guide...just where the parts are and how to change them. Test procedures are mostly done with Vag Com type (OBD2) program.

A general note: Electronics are heat sensitive and often only fail (in early stages) at high temps.
I was going to guess power output to the ignition coils when hot, except that you say the car runs perfect till shut off(?)

agreed mate , Thanks for your input. Do you know where i can find a diagram to show my friend the location of the coolant temp sensor on the 2001 s8 i have search google and no luck yet. Does anyone have the service / workshop manual who can send the page just showing the location of the sensor , if if someone could describ its location.

Regards

Forgive the image quality...photo of computer image. Must remove the intake tube between filter box and throttle body to access the sensor...attached to coolant tube behind engine...4 wire connector. The sensor may be attached with a c-clip, rather than screwed into place. Here's a link showing one from an Audi V6 engine...which is similar (I believe) if not exactly the same as in the 4.2 V8...not sure, but it will be apparent upon inspection:

http://forums.audiworld.com/showpost...22&postcount=1

Can I assume a code indicated a bad sensor or incorrect/unstable temp gauge reading? ...with no sign of actual over/under heating?

Hope this helps.

I have to second the coolant temp sensor, its not common on the A8, but other audis do suffer from abnormally long crank times when they are faulty, and only when the engines are hot. Replace the sensor.

yep thats the pkan the sensors are on order but my mate woudl like the page in the manual showing where the sensor is, can anyone take a photo or scan a page showing the location of the coolant temp sensor please.

regards

Look back at post #5....that IS the only page in the manual that shows the location of the sensor...as clear as it's gonna get.

Plus look at the link, which shows the type of attachment it's likely to have.

Respectfully, if your friend is going to do his own work, he really needs to invest in a manual...it will pay for itself the first time he uses it.

Cheers

Hope my comments did not indicate a lack of interest.

Did your friend make any progress or resolve the "crank- no start when hot" issue?

Others here and elsewhere have a similar unresolved problem.