'89 C4: Front Differential Interlock Problems??
 

Sorry about the double post (also posted in 964 bbs), but I'm in a panic. My '89 C4 has 42500 miles on it. Today, on my way to work I had trouble after about 20 minutes of highway driving. It started to surge, hesitate, and buck - the alarm panel kept lighting up with the central alarm (!), ABS warning and the interlock indicators. After a minute or so (after slowing down and checking it out), the car settled down again. It felt like the front diff was grabbing and releasing in a pulse-like, jerky manner, and I thought I could hear the sound of solenoids engaging and disengaging. I don't know if it is related, but my radio wouldn't stay on during this time, either... Any known or easy fixes or do I need to go straight to the mechanic? Thanks.

I think that the distributor drive belt has broken or you have one spark plug wire shorting to ground. Start the engine, open the engine lid and look on the left side of the engine compartment at the ignition coils. There is an ignition amplifier clamped to each coil. Pull off the wiring multi-plug on one coil and compare the engine running sound, refit that plug and pull of the other one. If it dies, the belt is broken, if it sounds rough then probably a plug wire is faulty.
When you are doing this be carefull and do not get caught on the drive belts.