[s-cars] '92 S4 Stumble when Cold

[racingiron at comcast.net]

Just an update on my cut-out issue.  I dove into both footwells, and everything is tight and clean.  I put fuses in place of the thermal breakers.  The connector for one of them (S172, brown, second from left) seemed a bit loose, but I could see definite contact marks on both pins of the new fuse I installed.  That's power for injectors and MAF, so it's a prime suspect now.  I also checked the MAF and POS connectors, which all look good.  I checked the spark plug torque, and all were a bit loose, but not alarmingly so.  Finally, I just swapped in the entire coil pack from the '93 parts car (with new boots).

I've driven the car several times since the work, and no more stumble when cold yet.  I have had a single stumble on three separate occasions during steady highway cruise.  At this point, I suspect a bad coil in the original set (115k miles) and maybe another on the current set (190k miles).  To verify, I'm going to swap them again to see if the behavior comes back.  If not, I'll have a closer look at that connector above the ECU.

Beyond that, I've got several V6 POS units to try, if needed (the '93 has one channel already bypassed and a second bad one yet to be identified).  I also have new plugs to go in.  I'm trying to do this methodically to zero in on the component, because the '93 motor will eventually go into the urq, so I want to be sure it has healthy bits when that time comes.  I usually commute by motorcycle, so cold test runs during the week aren't plentiful, though this week's massive snowfall (rolling eyes) gave me several chances. Thanks for all the tips so far, and further wisdom is always welcome!

Eric R.
'86 urq
'92 urS
'93 urS