I have a '96 2.8 L quattro. For the past six months I would use 91 ocatane gas, but then I chose to try the regular 87 octane (trying to save a few bucks). After about 3 weeks of the 87 octance I got a couple of CEL codes, since then I have switched back to 91 octance. These are the engine codes I got:

1. P1606 - Rough Road Spec, Engine Torque ABS-ECU Electrical Malfunction
2. P0402 - Exhaust Gas, Recirculation Flow Excessive Detected

I still drove for about a month with these errors - I figured it was a bad EGR valve.

Now the car won't start - it cranks and cranks but won't fire up. It seems like there is no spark. Is there an easy way to check if my timing belt snapped?

Any other ideas?

Thanks for the help!

 

The switch between octane levels has nothing to do with it. The EGR code could point to a problem with it or a vac leak large enough to keep your engine from starting. If the timing belt snapped you would know it because it would sound and feel totaly different when cranking. Search for the 2.8 vacuum line diagram if you need to.