"Limp-Home" Mode
The first thing to do is check the fault codes. They should point you in the right direction. If they don't, or you need a quick fix on the road, there are some things to check. A fairly common cause of this is actually just a poor connection on the fuel pressure regulator, or the ground wire that comes out of that connector and attaches (usually) to the air accumulator on the intake manifold. The 20V is completely timed by the computer, so distributor placement doesn't have to be too exact. There is a big black connector that is a few inches in front of the distributor cap towards the front of the engine, this is the multipoint connector that has the O2 sensor, distributor controls, engine management etc on it. If that is half off or corroded/wet the car will act funny. Try taking that connector apart, cleaning it, and putting it back together. You might want to put in some anti-corrosion spray in there too.
