Stefan;

Congrats on the 1800ES and welcome to this forum!

That's a comprehensive recounting of your initial findings and work, and it sounds like you've got a good start...I presume you got the recommendation for cleanup and using the Deoxit from my SW-EM site, so you must have also seen the info for setting idle and links to the troubleshooting manual (Ref: https://www.sw-em.com/bosch_d-jetronic_injection.htm ). Checking and verifying sensor connections is good, but since you are just gaining experience with the D-Jet, I recommend only working on one sensor or item at a time, so that you minimize the possible uncertaintees when something afterwards is not right, and you have to check the "last item worked on". Remember also the D-Jet is an open loop system...there is no Lambda sensor checking the actual exhaust and making corrections to the injection, so the ECU calculates and actuates the Injectors based on sensor inputs, right or wrong...so it's crucial that they're right!

I would recommend you also check the Injector spray patterns to assure they are all clear and good...and install the correct replacement Seals for your configuration.

It wouldn't hurt to check and adjust Valves, but unless way out of adjustment, where there would be other symptoms, it's unlikely that they are the cause of poor running...its likely something with the FI Sys...remember pressure comes first and must be constantafter that, its sensors and connections, all of which should be clean and tight (that's where I recommend Anti-Corrosive Zinc Paste, NOT dielectric grease!, to keep all main Battery, Chag Sys, and FI Sys connections free of corrosion after bringing connections to shiny metal). Ref: https://www.sw-em.com/anti_corrosive_paste.htm Redoing the questionable harness pins and boots is a good way to keep questionable FI connections reliable. Parts of the harness are subject to thermal degradation in the engine compartment.

ECUs are highly reliable, but again, it wouldn't hurt to clean and preventatively treat the connector with Deoxit...

More later.

Good Hunting