I have a 1990 BII that has a rebuilt 2.9 L engine but I m having a problem with acceleration. I replaced the plugs and the wires are fine but I keep getting a lag in acceleration. Its like rpms would shoot up but the speed is lagging to accelerate. I m not sure whats goin on and also it wont let me go 55mph unless I floor it. Also whats weird is that it runs fine between certain speeds then it starts to lag. please help!

 

"RPM's shoot up, but speed is lagging" Do you have a transission or is it a miserable/PITA automatic. Sounds like the clutch is slipping.

 

With the truck not moving if you barely press on the clutch & you are able to shift from neutral to any gear, the clutch is shot.

 

i have an automatic 2wd bII. I already replaced the fuel pressure regulator and tomorrow Im goin to replace the fuel filter.

 

Check your timing. A few degrees off makes a big difference. Factory is 10 degrees, but a lot of people run the 2.9's at 12.