Stumped on Symptom

Anyone!!!!
So for about a year now I've been dealing with the issue of not being able to filup my tank all the way. When I do I get some loss of accelerationalong with hard shifting back and forth. 3 and 4th gear.
When I don't fill up
Runs like a dream. 3/4tank i have absolutelyno issues. I've chased down almost anything I can think of on the emmisuons side. Even speed sensors on the trans.

 

There are two M.I.L. TSBs related to this issue. The first, EG019-03, covers replacing the fuel filler neck, and the other, EG020-03, covers the vacuum switching valve.

 

Is the check engine light on?

Knowing that bulb can and does burn out, have you scanned for codes? Most local auto parts stores will do it for free.

 

Plus one on scanning for codes. I'd argue that anyone that owns a 20-ish year old truck should invest in a scan tool (rather than rely on an auto parts store), you'll save the cost many times over. Well, you'll save money if you don't just read the code and then fire the parts cannon at it!

I'm betting auto parts retailers LOVE scan tools. A bit like gunsmiths love Dremel. They both generate a lot of business.

What I am trying to say, long winded maybe, is get a scan tool. But come back here with whatever you find, or worst case whatever Autozone tell you the code is. Don't just go buy a part based on what the code says.