I recently got a 740 from 1986 with roughly 225000km. Overall runs well except a few random issues some of which I was able to trace down to deteriorated cables. So going to replace the engine harness and have already found a couple of excellent guides on this.

I am thinking of doing some cleaning and maintenance while doing the harness as I know the previous owner did not do much (also to facilitate the replacement of the harness). Although quite comfortable with tools and electronics I am a complete beginner with cars so looking for advise from experts out there on what to do and what not to on this 230E engine, any feedback would be greatly appreciated.

So far I have considered removing the intake, throttle body, oil separator, flame trap, hoses, tubes, and maybe injectors, clean all that and replace gaskets and seals where necessary. I will also be changing the main fuel filter and the in-tank pump (unrelated to the harness but needed).

Does any of the above sound like something to avoid for the less experienced? What else can/should be done as part of a similar operation?

 

idle air controller (IAC), which is located under the intake manifold. carefully inspect all the rubber hoses in the air intake path, and replace any that are cracked (such as the two connecting the IAC to the intake).

take lots of pictures as you disassemble so you can put it all back together the same way

 

Here's a few seals that should be replaced but are easy to miss...
- Oil dipstick tube O-ring
- Seals inside the throttle body (shaft seal and/or TPS seal if your car has one)
- Oil filler cap o-ring
- Any/all hoses related to EVAP (I have no idea what your car has/doesn't have)