HELLO TO ALL
I have just purchased my first MB a 87 560sel with 150k miles and a idle problem. I am a auto tech by trade but have never worked on BOSCH CIS systems before so I figured WHAT A WAY TO LEARN! This car has been very well cared for and looks new and has thousands of dollars of receipts for service,most I suspect are from this on going idle issue.
Problem is the car has a very rough idle and will eventualy die.It runs fine over about 1000 rpm. I have checked fuel pressure upper 6.2bar and lower 5.8 bar. idle switch is working,Idle air control working ,air flow pot.working,new plugs, wires, cap, rotor, O2 sensor,crank sensor,fuel accum.
The only way I can get the car to Idle smooth is to adjust the on off ratio to 0% rich,O2 flat 1v. If I lean it up to any % duty cycle and O2 osillating the idle will get so rough it will die.It seems to be over correcting and staying lean too long. Also the car will run fine when cold in open loop.