98 SSEI 315xxx kms

when car has been driven for awhile and has reached full operating temp it will idle a little rough every 15-45 seconds not bad enough to stall........... sounds like small misfire but not big enough to through codes any ideas??

new plugs wires new coil packs cleaned injectors cleaned intake/maf

Check your fuel pressure, could be a slow fuel pump or fuel filter. But seeing it does it hot that'* a long shot. I would pull the throttle body and clean it. Also check the PCV and EGR. EGR is a good possibility because it happens when it'* hot.

throttle body has been cleaned pvc is good and egr is clean...........I will try fuel filter nxt

maybe CPS?

Don't see that causing a rough idle. Hot also has me think coil or ICM.

hmm ok good to know!

When testing the coil (there'* a write up in techinfo/testing) try testing with the coils both hot and cold. Warm up a bit in the oven and test. then put in the freezer and test again. Compare the readings. I've seen many coils test good, only to start failing when hot.

its got to be ICM I guess, I changed coil packs though

it only idles rough for a few seconds like a small missfire than its fine again.......

My bonneville does the same thing, no codes. Its like it stumbles. I've tried replacing quite a few components to no avail.

Ya I hear ya I think its a common thing for these 3.8 series 2 motors was thing about replace Cam Positioning Sensor next but Im kinda lazy and its not the ezest sensor to change