'93 5.7l Suburban
Changing the ICM today. With cap and rotor off, what is the metal cylinder on the distributor shaft that rotates back & forth about 10 degrees, no spring. Is it supposed to move freely, I assume it has no spring. Mind binds/rubs a bit - is that normal?
Thank you!

 

Bumparoo
Looking at diagrams what I call a "metal cylinder" above appears to be the shield over the pick up coil. Should I be able to rotate a little or should it be solidly mounted? Also, it looks like the tip of the "star teeth" are rubbing one spot on the shield - could this account for rough idle at cold start? Maybe once it warms/rubs a bit it expands and no longer touches?? Grasping at straws here I guess.
Thanks

 

I doubt it. If the pickup gear is rubbing, not normal. Look to see if there is a hold down screw missing. It's been a long time since I had to replace a pickup coil, what I do remember is %^&*&^$#!

 

Yes it is normal for the shield to rotate as you described. However, the reluctor wheel teeth should not rub on anything. Is your distributor shaft loose if you wiggle it back and forth/side to side? Sounds like you may have worn out distributor shaft bushings.

 

Thanks Oldcat - this dizzy was replaced in 2005, 60k miles ago by our mechanic. Receipt shows it's a re manufactured one. I did not try the wiggle test but will do so at next opportunity & report back. For a long time (couple years?) truck has very erratic idle only at cold start; rev to 1500-2k for about 30 seconds and smooths out fine from then on. Smells rich when this happens.

 

Sounds like it's overfueling when cold. Check your engine coolant temp sensor terminals for corrosion. If there's corrosion there it will cause the coolant temp to read colder than actual and the computer will add more fuel.

 

Thank you - On the recent colder mornings it actually starts better and initially idles smooth at about 1k, then after about 10 sec runs bad again till it's rev'd as described above. Coolant sensor (on top of mani for ecu) was changed before and did not change condition. Seems to me when dizzy was last changed this problem went away for several years.

 

That is going to be fuel related.

 

If the reluctor teeth are contacting anything, it will induce false pulses to the ignition system and cause driveability issues.