Allanr

Subject is 1989 s4, 70,000 miles with recent timing belt change, new plugs, rotors and caps and plug wires. While crusing at 60 mph noticed a loss of power. Continue to destination (5 miles) and stop the car with engine running. definately running on 4 cylinders. Kill engine and remove wire from left coil, start engine and note the engine noise is the same, 4 firing. Kill engine, replace left coil wire and remove right coil wire. Start engine and it sounds exactly as before, engine running on 4 cylinders. Obviously not a bad coil. This is really confusing! Kill engine and replace right coil wire, start engine and back to eight cylinders firing. Complete trip of about 10 miles with no problem. What gives here, has anyone experienced a similar problem and found the cause?

John Veninger

Much better if you post this to the 928 list.

Your 89 has a temperature sensor on cyl. 4 and cyl. 8 just below the exhaust manifold to make sure all 8 cyl. are firing. If it senses a change (or defective sensor) it will shut down half the engine to prevent raw fuel from entering the cats and causing a fire.

Check out:
http://www.nichols.nu/tip633.htm