Hesitate when first entering the freeway, not choked correct

[LaGrasta]

Something new has been happening these past few months, can't figure it out.

Background:
186k miles
fairly new rebuild on rear end and trans
tune up just a few years ago, maybe 30k or so

I start the van, jump on the freeway and I feel it cut on and off, hesitate, shudder, etc. If I engaged the cruise, I can really feel it. It goes away in less than a mile and doesn't do it again until it sits overnight upon first start up again. Once warm it never does it. After arriving to work and it sits at work all day, ti doesn't do it either.

Maybe a "choke" issue?

[LiftedAWDAstro]

Well there is no choke on the fuel injected engines, but it does sound like an open/closed loop running issue. I am not real familiar with what sensors are used during open loop compared to closed loop so hopefully one of the more technical guys can help. Have you pulled any codes or pending codes yet?

[LaGrasta]

notice choke was in quotes, i wasn't sure what to call the process of "waring up" a FI. lol
no codes at all.

[LiftedAWDAstro]

I figured being in quotes meant you knew there wasn't an actual choke. Wish I could help you with more troubleshooting ideas.

[LaGrasta]

At first I wondered if one of the rear bearings were dragging, they weren't replaced when i rebuilt the rear end. What killed that theory is it never does it unless it sits overnight. Hmmm.

Anyone else have any guesses?

[Smiliesafari]

Run some "Seafoam" through it. Half can in the intake and the other half in the gas tank. It could be something as simple as dirty injectors.

[astrozam]

EGR valve perhaps? I'm not sure if the 98's were the same as the 95's but I remember having issues sort of similiar to that one time due to a sticky EGR valve...but I'm only takin a guess here.

[LaGrasta]

I have a new spider injector upgrade somewhat recent, but the EGR valve, hmmm. Let me gander that.

[v8famvan]

CMP retard issue?

[LaGrasta]

UPDATE: It turns out it was low on trans fluid

[okie1]

Thanks for coming back with the answer, might help someone down the road.

[LaGrasta]

So many miles later, the problem returned and became worse. It bucks when idling along, such as when on cruise control on freeway. Basically, it's noticeable when no or little fuel is being supplied. With this determination, I finally figured it out and 100% fixed it. The distributor was worn and needed replaced. $100 and an hour of labor and it is back to perfect. This was a long term troubleshoot experience. We're now at 221,000.