I drive an '86 740 non-turbo sedan. It's been a champ for the last 7 years. Recently the engine has starting cutting out for what is usually a fraction of a second. I commute on the highway so it usually happens at speed and the car hesitates and then just picks back up. The whole process takes less that 1 second. Only once has it stalled completely and that was in stop and go traffic. Also, the tachometer immediately goes to 0 when the engine cuts out and bounces back to full rpms as soon as the engine comes back. It's really an instantaneous pause. Because of the tach symptom I thought it was the ignition so I did the distributor cap and rotor, plugs, and plug wires, but the problem hasn't stopped (I used all Bosch stuff). I've considered doing the coil since it's the original coil and it's another ignition piece, but it seems unlikely that it's related. I'd like to have at least a theory before I decide on my next step.

Any ideas?!

Stuff that probably unrelated, but you never know: I changed the timing belt, front engine seals, O2 sensor, water pump... I think that's it... about 6-9 months ago and everything has been fine until recently. Oh yeah, a couple weeks ago I found the underhood insulation sagging onto the accelerator cable pulley and pulled all of the insulation off of the underside of the hood. I think it was this cutting out problem that made me discover the hood insulation... whether they're actually related is another story.

That's all I can think of. Thanks in advance for any ideas.