stupid question,

[dieseltech]

stupid question, I know the computer in the 1985 524td controls engine timing (limited) and the egr functions,

Q. does this computer store fault codes? if so, how do you retrieve them without a check engine light?

the car runs great, but at idle in traffic with aircon, on the engine will surge ever so slightly, +-25rpm continuously with compressor engaged. when compressor kicks off. smooth as silk.

things i have done to engine:
I do have the timing advanced to about 90mm of lift because the car had very bad performance, white smoke, hard start, and misfired at high rpm's. I advanced timing 2mm at a time till it ran good with no smoke on hard accel.

did a valve adjustment with go-nogo feeler gooahjez.

i do have the bmw cam lock, crank lock, and pump locater pin, so I know all the timing belt components are spot on.

thanks
chris