450 SL in Denmark

Hi,

following mail arrived today and I will ttry to answer here:

Peter wrote: I hope you are doing well. I take the liberty to reach out to you directly as a last resort before I have to surrender and send the car to the shop. But I totally understand if you cannot be bothered - you surely have many other things to do and tonnes of people like me writing to you all the time and you have already helped me a lot. But here goes: At idle:The engine runs fine at idle. Perhaps a bit rough when cold, but after a few minutes of warming up it is very smooth. The ECU idle potentiometer is set to the leanest position. If I click 4-5 times to make it richer the engine begins to miss and “puffs” out of the exhaust pipe. All connectors plugged in (temp sensor I and II and throttle switch)When going into D and setting off from 0 km/h it almost dies and I need to be very gentle on the throttle to get it moving. Once reaching 50-60 km/h it begins to even out and does almost pull as it should. Not a perfect linear pull, but better than starting from 0 km/h.  Disconnecting throttle switchI have tried to disconnect the throttle switch and as expected, it barely idles. Almost stalls. When I put it into D, it dies. I cannot even make it move - not even if I go very gently on the throttle. Disconnecting air temperature sensor (and with throttle switch back in)When disconnecting the air temp. sensor the engine almost behaves like it should. Fine idle and pulls away from 0 km/h without having to go easy on the throttle. Pulls very nicely all the way up and with a linear curve. Maybe not running 100%, but quite close. Pre-requisites

• Timing and dwell is exactly where it should be
• New plugs (NGK BP5ES)
• Fuel pressure is 2 bar and is stable when I rev the engine - also when putting the car into D. Have not checked it while driving (accelerating) because I do not know how to route the extended fuel hose out of the engine bay without it being bent or crushed by the hood
• Checked for vacuum leaks via brake cleaner and have found nothing - have not used smoke, though
• Have pulled off throttle housing and cleaned the TPS 
• New (never used and in Bosch original package) engine temp sensor installed 

Hi Peter,

please check first of all whether you have a vacuum of 500 to 600 mBar at MPS hose at idle. From what Then check whether all injectors tick by touching them - you will feel it. Then please verify ignition timing at idle and that you have correct ECU matching your MPS.

Hi Peter,

are you sure that ECU rheostat is at lean and not at rich position ? What sounds so strange is that with disconnected air temp sensor car uns well. That means 20% more fuel.

Hi Volker,

Just checked vaccum with this device and at shows around 180 mBar at idle.  

All injectors are clicking regularly and in an even pattern. Timing is according to spec.

ECU rheostat is turn all the way counter-clockwise (towards the left-hand-side). When I turn it clock-wise it begins to miss-fire (at least it sounds like that) after 3-4 clicks.

Hi Peter,
the device you use doesn't show values in mBar but in mmHg and inHg.

What did it show?

Regards
Norbert

Hi Norbert,

Please see the picture - now with an arrow indicating the level of vaccum at idle.

 

Hi Peter,

I read 160 mm Hg which means 210 mBar. Far too little for idle. Should be 500 to 600 mBar.