Look here: http://autorepair.about.com/library/firing_orders/bl-fo-9636.htm
I believe it's 1-6-5-4-3-2
For a 1990 Buick Century V6 3.3L engine, the manufacturer's recommended spark plug gap is .060" (1.52mm)
1-6-5-4-3-2
The firing order for the 1990 Buick Reatta, which is equipped with a 3.8L V6 engine, is 1-6-5-4-3-2. The spark plugs are typically arranged in a way that aligns with this firing sequence to ensure proper engine performance. It's essential to follow this order when replacing spark plugs or performing ignition system maintenance to avoid engine misfires.
1,3,2,4 that is the firing order.
the firing order is 1342
firing order is1432
diagram of firing order on a 1990 Oldsmobile cutless 3.3 engine
Go to Google.com and type in the words "1990 Geo Tracker firing order" and it will get you to a site that will tell you.
1,3,4,2
The correct firing order is 13726548.
Pontiac.on.nimp.org That's should help you with the firing order. KOCKNMOUTH