'86 MJ no power above 35 mph

[Rick A]

My truck only has 69,000 miles but I did rebuild the engine. The truck runs beautifully below 35 mph (even with AC), but when I put it under load it surges and sometimes misfires. I've checked timing and tried my best to clean the fuel system. It has the mechanical fuel pump (2nd one) and I've added a secondary fuel filter. This is the Rochester E2SE carb and I'm at the end of my competence on trying to get the thing to work properly. I can't afford to switch out the carb just yet. Is there such a thing as a person that can adjust this carb to make it work? 

[jdog]

V6? 4? Auto? Manual? If it runs great with no load but crappy with a load could be a sensor or timing.

[eaglescout526]

15 minutes ago, jdog said:

V6

He does say Rochester and mechanical pump for fuel so it’s the GM one. 
 

Little history, the carb sucks, not fun to work on and has minimal adjustments due to all the emissions stuff that had to be tied in. Often times an engine swap to a 3.4 with carb of fuel injection is the better route to take. 
 

But don’t expect too much power from the V6. It outputs less than the 2.5L. 

[jdog]

28 minutes ago, eaglescout526 said:

He does say Rochester and mechanical pump for fuel so it’s the GM one. 
 

Little history, the carb sucks, not fun to work on and has minimal adjustments due to all the emissions stuff that had to be tied in. Often times an engine swap to a 3.4 with carb of fuel injection is the better route to take. 
 

But don’t expect too much power from the V6. It outputs less than the 2.5L. 

True but I don't like to assume

[eaglescout526]

1 hour ago, jdog said:

True but I don't like to assume

I think it’s fair to here, haha. I mean luckily it’s not the diesel. 

[JYau]

Have you checked all the vacuum lines? There are a lot on that engine.

[zomeizter]

I concur that the v6 sux balls, especially the carburetor, but only when neglected. I recommend you ensure all the vacuum and emissions lines are properly routed in accordance with your decal.