MFI Idle Speed Adjustment

[M491Cabriolet]

Hi. I had to chase down some frustrating oil leaks on my 1972 MFI 911, so I decided to install RSR rocker shaft seals, adjust the valves, change the oil (using Mobil 1 0W40) and replace all the top-of-the engine oil seals and gaskets. While I was at it, I installed another distributor, since my timing was beginning to bounce. The car still leaks a tiny bit of oil, which is no big deal (albeit a bit frustrating after all that work). Beyond leaking much less oil now, the car runs also much better (seems to have much more power), which I attribute to the valve adjustment and timing/distributor change. The funny thing is that I have two new issues, which I'd like to figure out and resolve. They both seem unrelated, but started up only after I did the above work. Nothing related to MFI was touched and I had the injection tuned professionally not long ago.

the first problem is that my idle is now at 1,100, up from 950. I think the car is running a bit lean (more later). My question is, if I try to turn the idle speed adjustment screw on the MFI injection pump two clicks to the right (rich), would that have the effect of slowing my idle speed, or speeding it up? I hope the answer is that it would slow it down.

Second, the warm up system started acting up after the work. When the engine begins to warm up, it now runs poorly, sputtering and popping. If I disconnect the hose from the heat exchanger to the thermostat, it strangely begins to run perfectly after a bit. If I leave it disconnected, the engine runs fine from cold. I could leave it alone, but this tells me that something is not right anymore. I think the thermostat is now leaning out the mixture too much for whatever reason. I plan to remove the discs and clean the assembly, making sure that the discs are properly installed and all there (not too many, I hope). So, I'm wondering...maybe if I richen it up at the idle screw it will help by richening the system enough to mitigate the thermostat problem (leaning out the mixture too much when warm)? Any advice in regard? Thanks!

[356RS]

Your first problem, idle went up, could be the new distributor timing. Your old distributor most likely had a longer/wider advance curve due because of worn out parts.
The new distributor has a much tighter curve and when the timing was set at the max rpm's, 30 degree's @ 6000 (don't quote me on that) now when the engine goes back to idle your at a little more advance in the timing which will cause the idle to rise a bit.
To properly lower the idle takes an adjustment of not only the idle mixture screw on the pump, but adjustments on your old throttle body (6) air/idle adjusting screws.
But to answer your first question, yes, if your richen up the pumps idle mixture screw this will bring down the idle speed.
On the possible thermostat problem, I would first check and correct if necessary the timing and idle adjustments before you play with the thermostat. Do a search on CMA on the MFI system, this will help you on what to check first, and in order, before you start looking at the thermostat or MFI pump.