Engine Misfiring at Light Loads '93 5.7 Engine

At about 1500 rpm in top gear, at a steady speed, the engine misses causing the car to buck. Switching to D2 or third gear, causes this to go away--rpms are higher in D2.

Any suggestions? I've changed plugs, plug wires, distributor cap, rotor. I do have the initial timing at about twice the recommended setting.

There are no codes indicated.

Sounds like an overdrive issue. I have a 92 roadmaster, same thing. Mine only does it going up a hill, I just downshift.

I don't know why you have the ignition timing set like that? I guess that is a story for another day.

The problem feels like an ignition misfire.

If the timing is set beyond the 6 degree recommended setting, does this cause other problems? I set it this way because with the reman engine, fuel economy has never been as good as the original engine. I used to get 24 mpg highway. Now it's about 20 mpg.

Mine is the overdrive, feels like the engine is cutting out. I shift out of od till I gain some speed then back to OD. Always on the same hill, in town, speed limit slows me down.

That timing issue doesn't sound right to me??

I read about a similar problem on another forum related to the EGR valve. I disconnected the EGR and blocked the vacuum line. Problem is gone!!!!

I'm wondering if there are consequences for disabling the EGR. If the only consequence is higher emissions, I'll leave it as is. Car runs perfect!