Warm Idle Mixture

[Gary Crutchley]

My ’65 230SL (manual) starts easily hot or cold, runs beautifully at high and low speed, idles beautifully when cold but has just one little glitch – when I pull away after idling for a few moments (such as at traffic lights) it will cough, splutter and hesitate slightly and then all is well again.  The only way to get around this is to anticipate the change in the traffic lights, give it few quick revs and then pull away (very undignified).  My suspicion is that it’s idling a fraction rich when warm.  I’ll admit to being totally out of my depth with fuel injection and I’ve read and searched high and low in this forum for a solution and in the process learnt a whole more about our cars – but not a solution to my problem.  Is there a warm idle mixture adjustment screw (if so a photo would be helpful) and is it reasonable that I could adjust this incrementally to see if there is any improvement.  Or should I l take it to a specialist who I suspect will jump in the car go for a good blast around the block and not even experience the cough/splutter hesitation.  Many thanks in advance.

[stickandrudderman]

It sounds weak rather than rich.
As an experiment you could try adjusting the linkage so that you get a weak or rich bias and monitor if and how the symptoms change, or you could just use the fuel adjuster on the pump to bias it. Either way should yield results.

[wwheeler]

My car had this same problem and noticed it after I bought it. It ran lean only at warm idle and fine everywhere else. It stumbled just as you say. You can adjust the the idle mixture at the FIP (only when engine is stoppped!). That only effects the idle warm and probably cold idle as well.

However when I dug deeper, I found a whole can of worms that needed to be fixed. I followed the linkage tour and found that the PO did all of the classic "sins" of linkage adjustment. I got those worked out and kissed that problem goodbye.

Depending on how confident you are that your linkage is set up properly, you might go through the tour. Solves many mysterious problems.

[glenn]

Check the WRD- Warm(willnot)Running Device.  See 'Search'.

[Benz Dr.]

If the throttle valve and the lever on the IP don't open at the exact same time you will often get that little sputter as the mixture goes lean or very rich - depending on how much it's off. The only way to get good off idle throttle response is to have everything adjusted perfectly. It's not that hard to do.

[Gary Crutchley]

Thanks guys,  I think that Stick and Wallace may be correct in that it’s lean and not rich as there no fuel smell (when soft top is down) or rich looking exhaust .  I’ll have a very careful tinker over the weekend and let you know how it goes.  Thanks to all of you for your responses.
Cheers