Hi guys, Lately I've been noticing my 1990 7.3idi is exhibiting a strange behavior when switching over from high to low idle. Here's the proceedure leading up to and including the symptom: 1.) Cold start the engine and the high idle/cold advance appears to be working normally with my engine idling at a higher rate than when warm. No noticeable stutter or rough sounding idle. 2.) Drive the van home from work at night with ambient air temps usually around 35-50°F. 3.) About halfway home (usually 10ish minutes into the drive) the high ideal will abruptly switch off with an audible "thunk" noise coming from under what sounds like the drivers side fuse box. When this happens my headlights will severely dim and power to the engine drops significantly for maybe 1/4 - 1/2 second before recovering to normal operation. 4.) After the recovery my lights and engine are operating normally and there does not appear to be any additional issues. It only happens when things switch over. Thoughts? I'm thinking either the high idle solenoid is going bad/has a bad connection but wondering if anyone else has experienced this. Thanks!