The SES does NOT blink for a P0442.....it blinks/flashes for a misfire.....

I was just stating that was the only code I currently had. It must not leave a code for a misfire. I did pull all plug wires off and one had some gunk on the post so I cleaned it and I have not had anymore miss fires. Still don't know on the jerking motion.

95% likeliness it is one of three things:

Bad spark plug wire
Bad spark plug
Bad coil or corroded coil connection to plug wire.

Save some time, replace the plugs and plug wires- problem will likely be gone, if still happening time to troubleshoot the coils. Very common issue on your year Bonneville.

That is my plan for this coming weekend. Thanks for the tips.

Let us know how it turns out, good luck!

Seems this is more common than you think but with no immedite solution. I have (2) 2003 Bonneville SLE'* and they both do this. right around 4200 rpm. Both have had full recent tune ups (plugs,wires, filters, intake gaskets, FPR etc). They run great except for this condition. The two possible answers I have got is fuel pressure related like the pump is weak and the catalytic convertor is clogged. Have not had a chance to check the fuel prssure yet. Not really an issue, Maybe slows the kids down a little. Really would like to find out though. I am thinking that the one with 180,000 probaly needs a converter but lot of money to spend and find out that is not it.

So I have a P0306 code. Misfire in cylinder 6. Where do I start?

If you already changed plugs and wires, exchange the coil on cyl 6 with another coil and see if the misfire moves to the new location. Have you checked fuel pressure?

No I have not changed the plugs and wires yet. I just bought the stuff and am gonna do it now.

Changed out all plugs and wires and the car is running absolutely great. Thanks for everyone'* help.