After letting my 86 NA sit for a couple of weeks, the battery was dead. Upon starting it with jumper cables from another car, the engine ran rough and had a noticeable slapping/knocking sound coming from the area of the timing belt.
After a couple of minutes, the noise went away and the car ran fine.
I had a Ford truck once that did the same thing and I was told that the computer had to reset itself and this was normal.
Is this true with a 944?
Also, with all of the electronics and electric fuel pump on our cars, can a 944 with a 5 speed be push started if the battery is completely dead?

 

When I have have my battery disconnected it takes the Dme a little while to relearn the idle. Not sure about the noise.

As far as push starting I have never done it. But I would think as long as alternator is turning fast enough it should start.

 

Probably just needed time for the lifters to pump up. Common even on new lifter if the car sits for a while they can drain. After a 1-3 minutes they should pump up and the noise should settle.

 

If mine has had the battery disconnected or dead for a while, upon restart it takes the car a few hours to act normally again.

 

Hmm do you know if it was coming from the timing belt cover or the cam housing. It sounds like the lifters needed to get lubed again. Have you started the car again when it was cold? If it keeps on happening then maybe it's time for a retension for the belts. They would slip if it's loose but the lifters should be fine now. Also if the battary isn't fully dead then you can push start the car but if it's dead you will have to have a good rolling start probably need to get up to 15mph atleast.

 

Is that slapping noise kinda random and sporadic? If it's a regular tick-tick-tick or clack-clack-clack that goes up with RPM, then it's probably your lifters. But if the noise is more banging and slapping like with irregular parterns, then it's most likely the timing-belt. That slapping noise is probably a loose timing-belt. As the engine warmed up and expanded, it tightened up on the belt and the slapping went away.

Also there is absolutely zero learning-capability in the Motronic v3.1 we have in our cars. I've examined each and every single component on both circuit boards. There is no memory devices of any kind to store and modify settings on the fly. The chips' program-code and data-maps are hardcoded in ERPOMs. The CPU does have some 8-bit registers, but that's all for storing instructions (assembly).

There is however, some small memory in the KLR to store fault-codes. And I recall reading some fault-condition that hangs up the KLR and requires unplugging it from power to reset.