Blue - you're burning oil
Black - you're running too rich
White - you're blowing steam (coolant vaporizing in the combustion chamber)

 

the smoke is black, but as i said this occurs when i have to literally floor it to start it. It doesnt blow smoke any other time. Does this help at all?

 

Offramp, you're on to something with this statement:

"There are too many factors: like how hot is the engine, how long was the engine shut off, 5 minutes might not be enough but 15 to 30 might be long enough. Outside air temperature is also a factor."

Because if I park and go into a store for 10 or 20 mins it doesn't cause a problem. But when the car sits for more like an hour it has alot of trouble starting. And if it sits for a few hours, and cools way down, it starts up great. Also it will go through cycles while im driving. After the car is completely warmed up it will run kind of crappy for a few miles, then it will return to normal. This only happens when the engine is completely hot, like when I've been driving for 20 + mins.

Please let me know if this makes any sense to you.
Thanks alot,
-Matt

 

If it takes an hour for the problem to rear it’s ugly head then it might not be vapor lock. It might still be a good idea to check the residual and system pressure but the problem might lie elsewhere. If the check valve is bad it shouldn’t affect the driving cycle because the pump is running.

Generally speaking what I often notice on older vehicles is electrical problems due to oxidation. Especially the ground points. If you live in an area where lots of salt is used during winter check all the electrical connections.

 

Unfortunatly yes, Upstate NY! Lots of salt here. But, does it make sense that this would only cause a problem when hot? If there was corrosion it seems as though it would be a problem all the time... Let me know what you think, Thanks alot.

Also how hard is it to change the check valve, where is it? I might just change it and see what happens. Is it in the back near the pump or near the engine?

-Matt

 

I have checked alot of other Audi forums and many other people have had the same problem. They lose fuel pressure too early when the car is off. If the car sits long enough it cools down and the CSI (cold start injector) sprays extra fuel into the intake tract. But it doesn't spray when the car is hot because ideally there would still be fuel in the rails/injectors ready to be dumped into the intake tract when starting.

So, since my car looses pressure before the engine has a chance to cool down, when I go to start the car there is no fuel readily available for the engine, and the CSI doesn't spray because the engine is still hot...

Other people have rigged the CSI to a button in the car. So they can activate it even when starting the car, when hot. Has anyone done this or would anyone be able to give me some info on doing this, my repair manual won't be delivered for a couple of weeks and I have no clue where I could tap into the wires for the CSI. Anyone with a book on a 1992 100 would be a huge help to me!
Thanks alot,
-Matt

 

You can buy a one way valve and instal it at the entrance of the fuel rail. If you feel that fuel is going away. But remember that you have electric fuel pump and each time you turn the key on it pumps fuel in.
You should look into engine electric schematics, particulary stuff for starting up. Or run a diagnostic using Vag com

 

I am not sure where the check valve is located on a 1992 100. Usually there are few, the filter has one and some fuel pumps had them as well.

I don't recommend bypassing the CSI as you want to cure the disease and not just treat the symptom.

Oxidation on sensors and connectors can provide the wrong signal voltage to the ECU. This results in the ECU going into all sorts of funky modes. I think on your 92 you should be able to flash some codes without using the expensive VAG tool.

 

How would I "flash codes?"
Thanks for all the help,
-Matt

 

It is easily done on the 91 and earlier models but the 92 and later use a different fuel injection system and I am not sure if the same procedure would work. You might want to check this link to get some idea as to how it is done. It may or may not be the same procedure.