305 engine
new tranny
oil change and tune up this week
has newish fuel pump(less thank 20k miles) and new fuel filter
had to replace tank for a new one as filler neck broke

Start going normally and at 20 it just seems to slow down for a few seconds and then starts to pick up normally again.
also feeling less overall hp

Thank you

 

Is this while the trans is switching gears? I am assuming its an automatic.

 

no it doesn't change gears until 40ish

 

So it is an automatic. So it will not shift into 2nd gear unless you are doing 40 mph? How do RPM's look and engine sound while this is happening?

 

my rpm gauge is retarded and always show max rpms whenever i press the gas. Sounds fine except from 20-25. Its a tbi also. I dont fell the shift until 40. This tranny has 3 days in it.

 

You got my scratching my head on this one. I am guessing it is transmission related since it only happens at a specific speed. It would be nice to see what RPM's are doing. Does the engine sound as if it is decelerating at this point? Misfiring? Can you be a little more specific with how it sounds? By new trans do you mean a rebuild or a brand spanking new one? What trans is it specifically?

 

Do you have a vacuum gauge that you can monitor while driving it?

 

ok found 1 spark plug wasn't changed in(was sitting by the battery in its box)fail with the tune up took it back and its not stalling at 20 anymore but still feel like it has less overall hp then it did a week ago.