The diagnosis is complicated by a few factors:

1. The day it happened I was using 87 octane, not 91 for the first time (though I understand that the car should run OK with 87, and I have now put gas line antifreeze and water remover but it didn't help).

2. It was raining pretty hard and I don't know how well the sealing rubbers work on the leading edge of the hood (but it has been dry since then and the problem still exists - I did get the car rustproofed and they did spray in cavities around the motor, but that was 2 weeks ago?)

3. I have pulled the cap and rotor they seem OK, and the plugs are new and seem to be a healthy tan shade. I did check it out in the dark, and observed no sparks.

4. It only screws up under load, in neurtral I can rev it out, but it only takes a light touch on the pedal to do it.

5. I did unplug my idle speed controller box (mine needs a repair) and aside from theidle jumping to 1500 rpm, the car ran just as poorly.

I am going to do the filter tonight, any other clues? I may get someone to sit in the car in drive, get it to misbehave and check the spark with a timing gun.

I don't know what else?

Antone know where the idle speed controller box is on an SL? I may wish to swap the out just to see.

thanks for the suggestions,

John