MJ not running properly in first and second.

[90manche]

My 1990 Comanche with the in-line 6 and manual tranny is not driving right, when I put it in first and second and let out the clutch it barely will stay running, I have to feather the clutch to keep it going, as soon as I get to 3000 rpm it runs fine in both gears, and it runs fine in 3+. I can rev it with the clutch in no problem. Any ideas? 
 

(is this the right place to post about things like this?)

[Ωhm]

Check vacuum hose  between manifold and MAP sensor for leaks or plugged line.

[Warren Mohler]

if you changed CPS since your last post about not starting proper, make sure CPS wire is not against exhaust manifold, check that vacuum line as Ohm suggests also make sure throttle body and IAC are clean---also does cat converter rattle?

[omega_rugal]

you mean it runs but lacks power?

 

there´s a vacuum leak in MAP or bad Throttle position sensor but since it can rev up to 3000 rpm fine, my vote goes for the MAP sensor vacuum leak, without it the ECU can not guess how much load is on the engine...

[90manche]

(Warren) I have one ordered, hoping to put it in this weekend.

 

(omega) if I don’t feather the clutch it will die, if I put the clutch back in it is fine.

[Minuit]

A nearly identical problem in my '89 ended up being a pinhole in the vacuum line running from the throttle body to the MAP sensor. Very hard to see, but it was there.

[cruiser54]

6 hours ago, Minuit said:

A nearly identical problem in my '89 ended up being a pinhole in the vacuum line running from the throttle body to the MAP sensor. Very hard to see, but it was there.

Yup. 

[MiNi Beast]

^so not bad driver?