Idle mixture adjustment question

[miked_md]

I have been trying to get the idle correct on my 230SL.  The best I can get is 1200 rpm and 17 mm vacuum with the mixture screw turned CCW to the point that it no longer clicks.  Splitting the linkage I can get another 200 rpm opening the throttle.  This is with a fully warmed up engine.  The dwell and timing are correct and the engine runs well apart from the high idle.  When in gear (automatic) with my foot on the brake the idle is lower around 700, if I take my foot off the brake it will move forward and run at 1400 rpm without touching the throttle.  The CSS is working as intended.

Any suggestions on how to correct this?

During warm up the car idles at 800 however splitting the linkage and adding air it will rev to 1800 rpm, I suspect it runs richer during warm up but 1800 seems a little high?  The cold start valve seems to function properly without leaking.  I have verified that the WRD does shut off the extra air once warm.

I previously had a 280SL that would idle around 1200 when cold then settle around 800 when warm.  My 230SL seems to be doing the opposite!

Thanks,

Mike

[ja17]

Have you set up the venturi stop screw (linkage tour) ?  Also which ignition distributor do you have?

[miked_md]

The Venturi stop screw is set and double acting solenoid is functioning correctly.  The distributor is the 051 version.  I may check the timing again at warm idle with and without the vacuum line connected.  When initially set I used 30 btdc at 3000 rpm.

[ja17]

If you unhook the vacuum line to the distributor while the engine is idling. The rpms should increase. Hooking the line back up should retard the ignition and lower the rpms.

[miked_md]

Thanks Joe.  Yep checked the vacuum retard while double checking the timing.  I am beginning to wonder if the engine is running too cool.  I rarely see the gauge go to 180.  The WRD cuts off the extra air around 145 to 150 on my car, the car will run at that temperature and not get much warmer unless sitting still.  My current theory is that the WRD was still supplying extra fuel during my idle adjustment.  Then when sitting in traffic and warmed to 180 the car was running too lean.  I’ll check the thermostat and see what I find.

[ctaylor738]

A couple of suggestions:

Check that the rack is moving freely.
Be sure that the injection pump lever is on the stop at idle.

Cheers,

CT

[miked_md]

I took the car out yesterday for a 15 mile drive to get gas and get it warmed up.  The car ran fine but it never got above 150.  After stopping I let it idle and got out my heat sensor.  I checked WRD, and the top of the radiator both were around 150.  While idling it eventually warmed up to around 180 and then the idle changed dramatically.  I stopped it and did a few idle mixture adjustment cycles to get a good idle.  The idle mixture had been set too lean previously due to the WRD still allowing extra fuel because the temperature cut off had not been reached.

Figuring I had a bad thermostat I decided to remove it and test it in a pan with hot water.  I removed the thermostat housing top.  See the picture below for what I found!