I'm not really interested in performance enhancement myself, I've been told by one garage that I need new coils, another tells me I don't. The idle is occasionally rough and I've done everything else but change the coils. Is having bad coils damaging to the engine? Does it cause problems with output/performance other than just a bad idle?

The techinfo article shows how to test the coils.
http://www.bonnevilleclub.com/forum/...e=article&k=33

That'* a good start, but ac (or pulsating dc) impedances can be complex and not always show problems with a dc resistance check. Nor will any breakdown caused by high voltage. Swapping them out with known good ones is the best way. Know anyone that you can swap them around with?

A few years back, there was a link posted where you could check for any updates to the programming of your PCM. Mine showed one for a change in the injector pulses to smooth out a rough idle problem. That'* a possible cause for yours. Mines does it a little in park, but smooths out in drive.

Need coils? I happen to have some laying around. They are also listed in For Sale section. Price is much cheaper than new.

Well, if the only problem with bad coils is that you have an occasioanl rough idle then I don't see the point in replacing them. I looked at the TECH INFO section about testing them, but I don't have access to that device. No other 3800 S2 friends either (most of my friends drive Hondas. ). I wanna say Pontiac was gonna charge me $600.00. Is that about right?

List price on the coils (p/n 10477602 for yours) is $73.76. www.gmpartsdirect.com has them at $38.36, and www.rockauto.com is $46.79 each. Even if you buy 3 new coils, you're in just a little under $600.

I swapped mine for MSD'*, but only because my stock ones were rusted and not making contact. Plus anything red under your hood is good for at least 8 whp.