260E Rough Idle Issue

[Athienou]

Hi.

Wondering can anyone help.

I have a 1989 260E. M103 Engine (No O2 Sensor)

I have a rough Idle with an occasional stall for the past 2 years that I’m desperately trying to figure out.

The revs on warm idle are at 500 RPM. It has a slight shake. I cannot identify if its an Ignition, Fuel or Vac Problem.

Ignition

Checked individual components and all appear to be working fine. The spark appears to be strong on all cylinders. I changed the plugs (Denso Q16TT) and distributor cap (but not the Rotor). Also replaced OVP.



Fuel

I‘ve changed the Fuel Filter and Fuel Pump Relay. Checked Accumulator. I’ve done several tests in terms of fuel pressure and flow. Fuel flow produces 2 litres of fuel per minute which is a good indication of strong fuel pumps. I did a pressure test on the KE Jetronic /Fuel Distributor. On the lower chamber I get 5 bars and on the upper chamber with the EHA disconnected I’m getting 5.4 Bars.

I ‘ve also replaced all injectors (Bosch x 6) and seals.



Vacuum

I’ve done a Smoke Test and it shows no leaks in the Engine Bay. I carried out a Vacuum Pressure Test from the Intake Manifold. Interestingly it went from 14hg to 15 Hg fluctuating between those points. (Have a Video if anyone’s interested) I believe it should be between 18 to 21 Hg and steady. The Vacuum Dial at that pressure indicates Late Ignition Timing.

I’ve also conducted a Compression Test and that indicated 13.5 Bars of Pressure on all six cylinders.



Other Components Tested

I’ve conducted tests on the following and all appear to be working

• The E.H.A
• The ICV Valve
• Potentiometer
• Temperature Sensor
• Crank Shaft Sensor
• Micro Throttle Switch
• Sensor Plate
• HT Leads ( Measuring Resistance)
• Duty Cycle
• Air Intake Temperature Sensor

I’ve run out of ideas at this stage and desperately want to get to the root of the problem.

Thanks for reading.