1,5.3,6.2,4
The firing order for the 4.3L engine is 165432
18436572
1-8-4-3-6-5-7-2 Rotor turns clockwise.
I believe it is 18436572 1.8.4.3.6.5.7.2
Same as all GM 4.3 vortec V6's: 1,6,5,4,3,2
Firing order 1-6-5-4-3-2
1342
1-6-5-4-3-2
18436572
1-8-4-3-6-5-7-2
If your 1997 GMC 5.7L Vortec has a misfire at an idle but not while under throttle, the problem is likely the timing. This can be adjusted.
gmc jimmy1989 firing order spark plugs