I have a 1992 960 Volvo with a loss of power and engine vibration throughout the RPM band. It occurred shortly after hitting a large pothole full of water.
I had no "Check Engine" light on but had an OBD I code of 2-1-4. Since the car has 168K on it I replaced the RPM speed sensor. The OBD I code has not returned.

I incorrectly thought my timing belt had jumped a tooth or two. I was looking at the wrong crankshaft pully notch (ignition timing) and not the little notch on the crank timing belt cog.

I have cleaned the connectors for the RPM sensor, AMM sensor and IAC.

I checked the spark plugs and coil wires.

Engine mounts appear to be OK.

I tried a can of dry gas and acan of Gunk gas treatment/injector cleaner.

I tried the Italian tune-up: running in L at 5000RPM for 10 minutes.

STILL NO CHANGE IN POOR RUNNING

The exhaust pulsates and the engine is rough at idle but smooths out around 5000 RPM. Gas mileage has dropped. It appears to have lost some power and downshifts more frequently on hills.

I am getting no OBD I codes from A2 and no "Check Engine" light. I thought these cars were supposed to self diagnose.

Whatcan possibly be causing my problem. One day it is running smooth as silk getting 26mpg at 80mph. The next day it is running like crap.

I'm supposed to be driving it to Montreal (300miles) to a hockey tournament this Friday.

Any thoughts. Please Help!!!!!!!!!!

HELP