Help! Why is my car stalling??

[bhatt]

Hello all,

I'm stuck.. broke my car and have no idea what I did. Any help would be MUCH appreciated.. especially before Monday when I take it to the mechanic!

1990 300SL. Replaced the Mass Airflow Potentiometer a year ago. Ran OK, but never got it adjusted properly. Mechanic told me to get a new airflow meter unit with a pot attached and just swap the whole unit.

I did that this weekend. Pulled the old one off and found the new one wasn't exactly the same so I couldn't use it. Put the old one back on and reconnected everything as before.

NOW THE CARS STALLS AT IDLE!

I couldn't get the car to start at first (it would catch but die before you could even hit the gas to keep it running). Found that the "boot" on the bottom of the airflow meter wasn't connected properly around the throttle "pipe" so it was leaking air into the intake (ie. bypassing the entire airflow meter!)

Reconnected everything so the pipe has no leaks. Now the car starts and runs, but only over about 1000RPM.

If you let it get below 1000RPM, it starts to shake. Below 800RPM is in danger of stalling, and it definately won't run much lower than 700RPM. Need to keep your foot lightly on the gas otherwise the car stalls.

Any ideas??

I found a vacuum line I had cracked and replaced it. The only parts I touched were:

-2 vacuum lines (both reconnected and don't appear to leak)
-large round thing on the front of the airflow plate.. seems to be some kind of fuel control valve
-EHA on the back - unscrewed it and reattached it. Connector is attached to it firmly.
-Air cleaner including the air temperature sensor connector. Connector is reconnected firmly, not that this should make much of a difference
-Separated the fuel distributor and reconnected it. All 3 screws are tight, and the O-ring is in place. It leaks no fuel, either from the lines or between the air flow meter and fuel distributor body itself.
-Some thing that looked like a PCV. It's a bit cracked and the hose has a small split, but it appears to be full of "oily air" and I don't think it's critical like a vacuum line. I think it is a PCV but could be wrong.

Everything looks like it did last night before I started. Nothing was damaged and there are no extra parts

Any ideas??? It sounds to me like a vacuum leak but I can't find one. I did try spraying the 2 lines I disconnected with carb cleaner, but it didn't make a "big" change. It might have affected the car by 100 or 200RPM but I can't tell since I had someone with their foot on the gas at the time (to keep the car running) and that may have been a variation with their foot.

Any help would be appreciated!!