'04 Grand Prix - Lucas Oil Stabilizer ----> car shakes?

I own an '04 Pontiac Grand Prix w/ 48,000 miles on it. I do my own oil changes w/ Castrol GTX or Mobil 1 5W-30 and a FRAM oil filter. For the first time, I added Lucas Oil Stabilizer (4 quarts oil and the LOS), and my has begun to shake when first started in the morning and sometimes throughout the day when I've been idiling for more than a couple of minutes. I'm going to change the oil again here soon, but if anyone has any reasoning as to why she's shaking after the stabilizer was put in, it would be greatly appreciated! I wrench on cars in my spare time, so I know my stuff ---- therefore, details would be great. Extras: fuel injectors are fine (also run fuel injector cleaner ever 3rd month to keep clean), just cleaned my throttle body and mass air flow sensor few weeks ago, and there is a new air filter. I usually run 87 (b/c she is a regular 3.8 V6 non-supercharged) and once a month put in 89 or higher (75%, I use Shell). Thanks for the help!'04 Grand Prix - Lucas Oil Stabilizer ----%26gt; car shakes?
just for the asking..where is your coil pack located..Is is by chance just above the oil filter..you could have bumped one of the plug wire connection to the coils..check this before changing the oil....and you might want to know this..adding quick cures in the bottles..do more harm than good..have you checked you oil level?when engine is cold? Is your check engine light on? Do this for me...crank car, holding brake pedal, put in reverse, still holding brake pedal with left foot and slowly increase the rpms with right foot...If rpms increase above 4 without any popping or missfire then you don't have a skip on a cylinder, but if you do, then thats your problem..If not a skip...when you cleaned your throttle body...problem might be the throttle position sensor..plunger might be getting stuck..or you might have a vacuum leak...all kinds of possibilities..get back to me and I can give you more testing solutions for you to run....IM me at gotspeed7883@yahoo.com